DTIC LD-A255 560 CT A RAND NOTE RJARS RAND's Version of the Jamming Aircraft and Radar Simulation William Sollfrey RAND wMm The research reported here was sponsored by the United States Air Force contract No F49620-91-C-0003 the United States Army contract No MDA903-91-C-0006 and by the Defense Advanced Research Projects Agency and the Director of Defense Research and Engineering contract No MDA903-90-C-0004 These federally funded research and development centers are sponsored by the U S Air Force the U S Army and by the Office of the Secretary of Defense and the Joint Chiefs of Staff The RAND Publication Series The Report is the principal publication documenting and transmitting RAND's major research findings and final research results The RAND Note reports other outputs of sponsored research for general distribution Publications of RAND do not necessarily reflect the opinions or policies of the sponsors of RAND research Published 1991 by RAND 1700 Main Street P O Box 2138 Santa Monica CA 90407-2138 A RAND NOTE N-2727-1-AF AIDARPA DR E RJARS RAND's Version of the Jamming Aircraft and Radar Simulation William Sollfrey Prepared for the United States Air Force United States Army Defense Advanced Research Projects Agency Director Defense Research and Engineering t DyrIC QUALMY aqpr- RAND 3T I TlvCodes 1 t APPROVED FOR PUBLIC RELEASE DISTRIBUTION UNLIMITED - iii - PREFACE RJARS is an engagement level model that simulates air-to-ground and ground-to-air combat primarily the latter treating the combatants as individuals rather than aggregating It has been designed to consider terrain masking multipath and clutter and flight dynamics in order to more carefully evaluate jamming effectiveness and mission attrition The model is an extensive development of JARS Jamming Aircraft and Radar Simulation which was originally developed at the Johns Hopkins University Applied Physics Laboratory The redevelopment effort began in 1989 for studies of electronic combat Funding for the multiyear development effort was provided by a coordinated set of RAND sponsors that included the Air Force Assistant Deputy Chief of Staff for Plans and the Assistant Deputy Chief of Staff for Operations the Deputy Director of Defense Research and Engineering Tactical Warfare Programs the Defense Advanced Research Projects Agency and the Army's Assistant Deputy Chief of Staff for Force Development This effort also drew on exploratory research funds from RAND's Project AIR FORCE the Arroyo Center and the National Defense Research Institute federally funded research and development centers FFRDCs sponsored respectively by the U S Air Force by the U S Army and by the Office of the Secretary of Defense and the Joint Chiefs of Staff The work was conducted through a series of related projects that included Electronic Combat in Support of Defense Suppression Operations Project AIR FORCE Concept Analysis Environment National Defense Research Institute Future of Army Aviation Arroyo Center and the Joint Close Support Project which is supported by all three FFRDCs The current version of RJARS considers sorties in which aircraft carrying warning receivers jammers anti-radiation missiles and air-launched cruise missiles fly against a defensive system with search acquisition and tracking radars IR and optical systems surface-to-air missiles artillery and a command control and communications system All equipment parametprq and scenarios can be varied The program is - fast efficient and compact iv - RJARS can operate independently or in conjunction with other simulations that have been developed at RAND In particular coordination with RAND's CAGIS Cartographic Analysis and Geographic Information System program enables the inclusion of detailed terrain parameters coordination with the flight planners BLUE MAX for fixed-wing aircraft and CHAMP rotary wing aircraft provides flight paths over the terrain including aircraft dynamics and coordination with JANUS allows treatment of air effects on ground combat This Note is an update of N-2727-AF December 1988 It should be of interest to analysts and mission planners who wish to treat air attack versus ground defense systems from either viewpoint to ascertain the survivability of missions against various defenses to evaluate the effectiveness of ground equipments in either the unjammed or jammed condition the effects of radar cross section the significance of cutting communications the results of changing any of the equipment or scenario parameters or almost any other problem which may arise in the treatment of such systems This Note describes RJARS as it was during September 1990 It is expected that there will be improvements and additions to the program Any reader who wishes further information should contact Dr William Sollfrey RAND 1700 Main Street Santa Monica CA 90407-2138 Telephone 213-393-0411 Extension 7222 - V - SUMMARY RJARS RAND's version of the Jamming Aircraft and Radar Simulation is a many-on-many computer simulation involving aircraft radars IR and optical systems jamming systems offensive and defensive missiles and a command control and communications system for the defense simulation can handle hundreds of aircraft and radars clutter and multipath are included The Terrain masking It is an extensive development by RAND of the computer program JARS Jamming Aircraft and Radar Simulation which originated at the Johns Hopkins University Applied Physics Laboratory Refs 1 2 RJARS has been designed to treat sortie operations and evaluate jamming effectiveness and mission attrition at a level of detail that includes reasonable refinements of equipment operation without excessive calculational complexity At RAND RJARS operates in conjunction with the Army's JANUS ground combat model the CAGIS Cartographic Analysis and Geographic Information System terrain model and several flight planners All operations of RJARS have been programmed both for independent operation and for use of these external programs A Revision Control System RCS keeps RJARS up to date and consistent for all users The parameters of all equipments aircraft receivers jammers airborne missiles radars and surface-to-air missiles SAMs are stored in library files that are updated and maintained off-line simulation is run under the control of a scenario i Among the scenario inputs for the offense are the number and types of the aircraft the equipments carried on board and their flight paths Flight paths can be described in terms of specified commands or may follow the output of an off-line flight path generator Aircraft can turn climb and accelerate turn jammers on and off enter or exit formation flying and launch weapons The defensive scenario includes the positions and types of all radars and missiles and who reports to whom launchers are at fixed positions All radars and SAM Infrared IR and optically aimed missiles and anti-aircraft artillery are included with a separate - vi - command structure in which they receive cueing data from the communications system The operation of the program may be understood by following a simple scenario Initially only the defensive long-range search radars and the searching optical systems are activated Suppose an ai-craft the term aircraft includes both fixed-wing and helicopters comes into the field of view of some radar A probabilistic detection will be performed which may take several scans to establish identification When detection is confirmed the radar will transmit this information to its site If the communications channel is working the site will report the new detection to its command site At the command site the information will be evaluated and if possible a tracker will be assigned from among those which report to that specific command site The terms tracker and tracking radar are used synonymously throughout this Note There are a number of conditions which must be satisfied for instance if a particular tracker is to be assigned the projeicted path of the aircraft must come within the maximum operating range of the SAM associated with that tracker When a tracker is assigned its associated acquisition radar is turned on after a delay determined by the communications delays uplink and downlink and the decision delay at the command site The acquisition radar performs a probabilistic deLecLion like that of the search radar and if successful turns the tracker on RJARS radars are multifunctional so one equipment may perform search acquisition and tracking functions The tracker then will follow the target with errors determined by target glint signal-to-noise ratio and jamming effects If the communications system had not been operating the scenario provides for cutting or connecting links at specific times the site will perform the assignment task autonomously using only the equipment that it controls directly Infrared and optically aimed weapons are controlled differently They search specified sectors using algorithms for detection and recognition of targets against sky or ground background If a target is detected and recognized either the IR missile waits for lock-on is - vii counted down and launches or the gun is aimed and fires If the optical signal is lost after recognition the equipment returns to search If any command system has detected a target the warning information is broadcast throughout the field If the target is potentially in range of a searching optical system the search sector is narrowed for improved detection While these defensive operations are proceeding the aircraft will continue their flight maneuvers They turn to the appropriate headings climb descend pitch bank or accelerate and launch weapons when commanded by the scenario catalog the information The warning receivers detect the radars and The jammers may be directed to jam radars of any or all classes search acquisition or track Jammers can employ noise jamming any combination of range or angle deception or one of several varieties of towed decoys depending on the capability of the jamming equipment and the choice of jamming technique designated by the library as appropriate for that radar by flares Infrared systems may be decoyed Rudimentary IR missile warning systems are on the aircraft and rudimentary flare rejection systems are on the IR missiles Jamming of infrared or optical systems is not included in RJARS at this time Deception is simulated by matching the jammer bandwidth to the radar bandwidth For search radars the effect on the probability of detection is ascertained For tracking radars the errors in range and angle are determined and the signal-to-noise ratio is compared to the breaklock level deterministic rather than probabilistic comparison Tf the signal to noise ratio is below the break-lock level in range or angle the tracker either cannot establish lock on the target or loses simulated lock if established and cannot guide a SAM if one has been launched There is no attempt to simulate the detailed operation of range or angle tracking circuits If a tracker is jammed while the target aircraft is approaching it will attempt to lock on to the aircraft for a time specified in the radar library while the target is receding it will drop track If it is jammed - viii - If a tracker establishes lock on its target for sufficient time it will count down and launch a SAM at the target found from a probability distribution Countdown times are Launch success is calculated by a random draw against the launch reliability If the launch is successful the SAM will fly on a trajectory in which its acceleration is determined by a thrust and drag program and its steering is either command-guided toward a predicted point of intercept or uses proportional navigation with a semiactive radar or IR system The SAM aerodynamics are represented by a first-order lag in the response to the guidance command The command data are corrupted by the radar errors When the SAM reaches its closest approach to the oriented target the miss distance is calculated by adding a randomly oriented normally distributed guidance CEP to the radar-produced error then calculating the kill probability as a piecewise linear function of the miss distance If there is an actual hit the kill probability is unity Otherwise a random draw against the kill probability determines the success If the aircraft has been shot down by the SAM it is removed from the simulation If not the tracker begins a second countdown or more if necessary Data have been collected on the effectiveness of jammers against various SAM systems These data may be used to determine the reduction in kill probability of a SAM rather than the detailed jamming calculations Data are available both averaged over all cases and as a function of signal-to-noise ratio If the aircraft are carrying anti-radiation missiles ARMs they may be launched at the trackers Frequently there is a close race with the ARM being launched first but with slower speed than the SAM If the AR'i kills the tracker another probabilistic calculation before the SAM arrives at the aircraft the SAM will lose guidance and continue ballistically Then if there is no interception following a specified time interval the SAM will self-destruct If the tracker goes off the air the ARM will continue its flight with reduced kill probability The alternate condition in which it diverts to another target was not implemented a limitation of the - simulation ix - Air-launched cruise missiles are treated as additional aircraft with their own scenario parameters ' The interplay of aircraft tracker and missiles continues until the aircraft is shot down or escapes from the region Terrain may be included in the calculation in several ways There may be no terrain with all calculations performed over a smooth spherical earth Terrain may be included directly with the elevation of the line of sight over the terrain between each aircraft-radar pair calculated at each time step and the result used to determine instantaneous visibility If the simulation is lengthy or repetitive operation is to be employed a preprocessor mode may be used to calculate the visibility intervals for each pair These visibility intervals are then used to control the main simulation Multipath and clutter effects are included in the radar calculations The ground defenses include not only radars but infrared missiles and optically aimed guns are included Background effects on such devices Terrain effects may be calculated using CAGIS which is more efficient than RJARS in finding visibilities between radars and aircraft or ground clutter points Also the ridges along various directions from each ground equipment are calculated preferably by CAGIS to determine if the ground is visible to the radar or if the optical system sees the target against a sky or a terrain background The sequence of operations as described will proceed until either the end of the simulation time is reached or all aircraft have been shot down During the run at scenario-selected time intervals information is printed out on the aircraft positions and maneuvers the search or acquisition radars' current observations the tracker measurements and errors the ARM's position and destination if launched and the SAM's position if launched When the SAM is closing on its target less than 1000 feet the details of the SAM trajectory are printed Events such as a detection launch or kill are printed as they occur 'RJARS addresses only cruise missile survivability not effectiveness At the end of the simulation summaries are printed showing all field of view entries detections and exits for each search radar and aircraft pair times of assignment acquisition and tracking duration for each tracking operation launching and result for each ARM and launch and intercept times and results for each SAM Box scores show how the aircraft fared in accomplishing their missions reaching destination surviving ingress and egress and how the SAMs performed their defensive mission Statistics on killing intervals and kill probability density may be collected When RJARS is operated in conjunction with the JANUS ground combat model these statistics are transmitted to JANUS for its use in determining the effects of coordinated air strikes on ground combat operations RJARS may be operated in Monte Carlo repetitive style of repetitions is specified in the scenario The number At the end of each run all the variables are reset to their initial values except the random number generator which is allowed to continue from its present value The resulting statistical information must be processed offline after completion of the Monte Carlo sequence except for the data transmitted to JANUS When operating Monte Carlo the details of the simulation are printed only for the first run On the ensuing runs only the status events detections launches etc and the summaries are printed RJARS now includes a graphics calculation This is provided as a file in CAGIS format and is the only nonportable part of RJARS With the graphics the terrain and defenses may be depicted on the screen along with the aircraft SAM flight paths and their interactions an aircraft progresses along its path it is initially in black As The path color changes to gray when a searcher detects the aircraft to blue when a tracker is in acquisition to yellow when a tracker is in track and to orange when a SAM or shell has been launched red SAM paths are in An endgame miss is a small red star an endgame kill is a large red star Icons are used for the defenses to indicate the type of radar SAM or gun Targets for the aircraft may also be shown Iterations may be presented in sequence The paths may be laid down all at once or the flights may be time-stepped The latter is usually much - xi - more descriptive The graphics operation is an RJARS postprocessor for which the data file is prepared during the RJARS run and th graphics program may be run at any time The variables treated stochastically are as follows Defense system element reliability A uniformly distibuted random draw against a reliability which is a property of the type of element Radar frequency A random value uniformly distributed over the frequency range available to the radar is selected Radar initial azimuth A random variable uniformly distributed from 0 to 360 degrees is selected Search radar probability of detection This is calculated by a formula relating probability of detection to signal-to-noise ratio then compared to a random variable uniformly distributed between zero and one If the probability of detection exceeds the value of the random variable a detection takes place Search radar errors The rms errors in range azimuth and elevation are calculated by formulas then multiplied by independent random variables normally distribLted with zero mean and unit variance Tracking radar errors Glint and noise including jamming are treated independently The rms errors in range azimuth and elevation are calculated then the current errors are determined using correlated random variables distributed according to three independent two-variable normal distributions with zero mean unit variance and correlation between the variables say the present and previous values of range error which depends on the glint frequency or servo bandwidth Anti-radiation missile kill probability The library value of the kill probability of an ARM of the appropriate type against a radar of the appropriate type reduced by a time-dependent factor if the radar goes off the air is compared to a random - xii - variable uniformly distributed between zero and one The library value is actually the product of the launch reliability and kill probability If the calculated value exceeds the random value a kill takes place Surface-to-air launch reliability The library value is compared to a random variable uniformly distributed between zero and one If the library value exceeds the random value a launch occurs Surface-to-air missile CEP This is treated as a vector whose magnitude is normally distributed with the proper rms value and whose direction is uniformly distributed over the unit sphere Surface-to-air missile kill probability This is calculated as a function of miss distance then compared to a random variable uniformly distributed between zero and one If the kill probability exceeds the random value a kill takes place Random phases for multipath or clutter calculations The radar operating frequency and initial azimuth are calculated at the beginning of the program and retained thereafter The other random variables are each calculated at the appropriate time search radar variables at each time step tracking radar variables at each time step when the tracker is on and each subdivided time step when a SAM has been launched reliability at launch and CEP and kill probabilities at the time of kill RJARS operates on UNIX systems in the C language Dynamic allocation permits RJARS to use the smallest amount of memory space compatible with the size of the scenario A more detailed description of the sequence of operations is presented in Sec II An analytical section Sec III provides the theoretical basis for the program A user's guide Sec IV shows how to prepare input files and operate RJARS A programmer's guide Sec V presents programming details and a glossary of the approximately 1100 variables used in RJARS Program flow charts appear in the Appendix - xiii - An implicit assumption in RJARq is that the laydown is truly known implying perfect intelligence It is also assumed that the offensive and defensive equipments are working perfectly ignoring problems of electromagnetic compatibility and electromagnetic interference other than jamming These problems may be considered in the future RJARS should be regarded as a simulation not as a true representation of the real world Further developments of RJARS are planned during the upcoming year The input data will be converted to a menu-driven operation that should be more user-friendly A statistics package will be added The radar modelling will be improved to provide better simulation for CW and pulse doppler radars Multipath clutter and electro-optical EO backups will be investigated The command and control will be modified to provide a three-level structure with intercommunications skip echeloning and other variations The aircraft vulnerability treatment will be expanded to include better dependence of kill probability on aircraft and missile type and a probability of kill given a hit model Target priority and firing doctrine will be investigated It is expected that this work will be funded from Project AIR FORCE and the Arroyo Center - xv - ACKNOWLEDGMENTS It is a pleasure to thank program directors Natalie Crawford and Bruce Don and project leader Fred Frostic for support in developing this improved version of RJARS Judy Lender established and maintained the configuration control system that keeps RJARS the same for all users Jack Ellis performed miracles of data collection and interpretation Keith Smith developed the coupling of probability effects between RJARS and JANUS Jim Gillogly originated the method of dynamically allocating variables The graphics were all developed by Gail Halverson Al Zobrist the chief modeler and developer of CAGIS performed yeoman service in the coordination between CAGIS and RJARS James Jennings and Sally LaForge respectively the adaptor of BLUE MAX and the developer of CHAMP labored to make their programs work in conjunction with CAGIS and RJARS The numerous users especially Bill Dean Ted Harshberger and Jerry Stiles found innumerable bugs before they became seriously contagious The comments of reviewer John Clark are much appreciated Anybody else who helped the author is hereby thanked anonymously - xvii - CONTENTS PREFACE SUMMARY iii v ACKNOWLEDGMENTS xv FIGURES xix Section I INTRODUCTION 1I II III GENERAL PROGRAM DESCRIPTION 9 ANALYSIS SECTION 23 A UPDCK--System Clock 23 B UPDAC--Aircraft Position and Maneuvers 23 1 Position Updating and Maneuvers 24 2 Flight Path Generators 28 3 Nonpositional Maneuvers 29 C UPDTR--Over-Terrain Visibility 32 D UPDRS--Update Search Radars 36 1 Signal and Jamming Power Analysis 37 2 Jamming Sequence 42 3 Detection Probability 43 3a Radar Cross Section 44 3b Measurement Errors 46 4 Output and Detection Table 47 5 Multipath and Clutter 48 6 Optical Systems 52 6a Detection Algorithm 53 6b Control of Optical Systems 59 6c Cueing by Communications Alerting 60 E UPDSI--Sites and Assignment 61 F UPDRT--Tracking Radars 63 1 Signal and Jamming Calculations 63 2 Tracking Errors 64 3 Conditions for Dropping Track 67 4 Interpolations and Correlated Errors 68 5 Towed Decoys 70 6 Semiactive Systems and Illuminators 71 7 Infrared Systems 73 7a Source Radiation and Attenuation 73 7b Signal Calculations 75 G UPDAR--Anti-radiation Missiles 77 H UPDSM- -Surface-to-Air Missiles 79 1 Sequence of Operations 79 -xviii - 2 SAM Propulsion and Guidance 82 3 Semiactive Seekers 87 3a Seeker Clutter 88 3b Jamming of Monopulse Seekers 90 4 Infrared Seekers 91 4a Flares 91 4b Signal from Target and Flares 93 5 Endgame 94 I UPDWR--Update Warning Receivers 97 1 Power Calculations 97 2 Receiver Decisions 98 3 Jammer Decisions 100 J OUTPUT--Print Summaries 101 1 Print Sequence 101 2 Statistical Calculations 103 K CALCSR--Auxiliary-Calculational Subroutines 104 IV V RJARS USER'S GUIDE 111l Preparation of Library Files 111l 1 Aircraft Parameters 112 2 Radar Cross Section 113 3 Anti-radiation Missiles 114 4 Infrared Parameters 115 5 Jammers 118 6 Terrain Parameters 119 7 Radars 119 8 Surface-to-Air Missiles 123 9 Warning Receivers 126 Preparation of Simulation Files 127 1 Terrain Data 128 2 Aircraft Radar Intervisibility Data 129 3 Ridge Data 130 4 Scenario 131 Outputs 139 1 Printed Outputs 139 2 Graphical Outputs 141 PROGRAMMER'S GUIDE 145 Glossary 149 GLOSSARY OF VARIABLES 151 Appendix FLOW CHARTS 175 REFERENCES 189 - xix - FIGURES 1 Connections Among Computer Programs to Form Land-Air Combat Model 2 Defensive Configuration A l RJARS Flow Chart A 2 GETDATA Sequence Chart A 3 Update Clock UPDCK and Update Aircraft UPDAC Flow Chart A 4 Update Terrain UPDTR Flow Chart A 5 Update Searchers UPDRS Flow Chart A 6 Update Optical Search and Acquisition Flow Chart A 7 Update Radar Search and Acquisition Flow Chart A 8 Update Sites UPDSI Flow Chart A 9 Update Trackers UPDRT Flow Chart A 1O Update Anti-Radiation Missiles UPDAR Flow Chart A 11 Update Surface-to-Air Missiles UPDSM Flow Chart A 12 Update Warning Receivers UPDWR Flow Chart A 13 Output and Monte Carlo UPDMC Flow Chart 3 12 176 177 178 179 180 181 182 183 184 185 186 187 188 - 1- I INTRODUCTION The original version of the Jamming Aircraft and Radar Simulation JARS was developed at the Johns Hopkins University Applied Physics Laboratory Refs 1 and 2 Its capability is well described by the following quotation Ref 1 page 1-1 The Jamming Aircraft and Radar Simulation JARS is a PL I computer program which simulates a many-on-many scenario involving support jammers strike aircraft and early warning radars that are netted to a user-defense system The program provides the user with the opportunity to evaluate jamming techniques and tactics against the radar defense system A probabilistic determination of target detection is obtained for each radar and each radar site against each aircraft Essentially the original version of JARS determines how aircraft carrying jammers will interact with search radars The aircraft fly prescribed paths and jammers are turned on and off under user control Only search radars are included and the aircraft and radars are immortal no weapon-type interactions The only significant outputs are the times in which aircraft are in detection and the times that radars are jammed JARS is an excellent program which performs rather limited objectives In the course of a study on electronic warfare it was decided at RAND that we would upgrade JARS to a full-fledged sortie simulation The resulting program named RJARS RAND's version of the Jamming Aircraft and Radar Simulation is several times as long as the Johns Hopkins version It enables us to investigate a much greater variety of offensive and defensive configurations and determine the effectiveness of jamming techniques including noise and simulated deception when the offense and defense are interacting RJARS can operate independently or in conjunction with other programs It has been translated into the C programming language to work under the UNIX operating system on the Sun work stations in the RAND Military Operations Simulation Facility MOSF As such RJARS -2- works with the Army's JANUS ground combat model to provide input threat laydowns and RAND's CAGIS Cartographic Analysis and Geographic Information System terrain mapping model to provide terrain and other inputs The flight path generators BLUE MAX fixed-wing and CHAMP helicopters associated with CAGIS can be used to prepare flight paths for RJARS Detailed procedures in CAGIS may be used to prepare the RJARS scenario and other input simulation files via automatic data preparation instead of manual calculation is written to be read by CAGIS The graphics output of RJARS While all of these have been very valuable to RAND's use of RJARS an external user who lacks these associated programs can still use RJARS by itself for everything but the graphics The interaction among the computer programs is depicted in Fig 1 The PL-I version of RJARS described in the first edition of this report Ref 3j was updated to include a few of the phenomena that were added to the C version in the period between June 1 1988 when the original N-2727-AF was actually completed and the present longer being kept up to date It is no Only the C version will be treated hereafter The C programming language requires that the names of all variables be fully qualified This would lead to very complicated description hence we have retained the PL-I type notation for the variables in the text For example the latitude of aircraft J is designated ACLAT J rather than the full C name AIRCRAFT J AC LAT The glossary at the end of the programmer's section lists all variables in the PL-I notation with structures represented in the first two or three letters of the variable name The aircraft now carry warning receivers jammers under warning receiver control towed decoys air-launched cruise missiles 1 and anti-radiation missiles The ground-based defensive system includes search acquisition tracking and illumination radars IR and optical 'Air-launched cruise missiles are treated as additional aircraft with their own scenario parameters It is their survivability that is being assessed not their effectiveness -3- JANUS Ground combat model Aircraft beginning and end points Threat laydown CAGIS Geographic model Flight paths Reduction of threat laydown Lines of sight and ridges Scenario RJARS Surface-to-air and electronic combat model Detailed interactions Kill probabilities Graphics 7 Fig 1--Connections among computer programs to form land-air combat model - 4 - systems surface-to-air missiles anti-aircraft artillery and a command control and communications system Terrain is used to determine masking clutter and multipath effects may be operated in Monte Carlo fashion The entire program Input data are contained in two types of files--library files with the properties of specific equipments and scenario files for particular runs RJARS may be employed to investigate a great variety of problems that require an intermediate level of detail Some potential applications are the following 1 Medium-scale attrition studies Flights of aircraft carrying jammers and anti-radiation missiles ARMs may be operated against surface-to-air missile SAM and anti-aircraft artillery defenses and the resulting attrition and mission success ascertained RJARS employs dynamic allocation for its variables and its problem size and speed limits are set by the properties and load of the machine not by any inherent limitations in the program Such attrition studies would be of value to mission planners 2 Jamming effectiveness studies Aircraft may be flown with different jammers and the corresponding mission successes compared The effectiveness of jamming techniques can be investigated The absolute and relative effectiveness of various jammers would be valuable information to both mission planners and equipment designers This assumes that the response of the several types of radars to jamming techniques is known The real world may be very different from the world of the simulation 3 Effects produced by terrain of primary interest for low-flying aircraft missions The delays and interruptions in radar coverage produced by terrain masking and the resultant changes in defensive capability can be evaluated to determine appropriate routes for attack missions The effects of clutter or multipath on the radar configuration can be determined -5- 4 Radar cross-section effects The improvement in mission success--of the aircraft reaching target or surviving the mission--produced by reducing the radar cross-section of the aircraft can be studied 5 Communications cutting effects RJARS organizes the defensive system so each radar and each SAM launcher reports to a site and each site reports to a command site Communications proceed upward from a site to its command site describing the detection of aircraft and downward from a command site to any of its sites describing tracker assignment There are delays on each link and a decision delay at the command site typical configuration is shown in Fig 2 p 12 A When communications links are cut RJARS sites revert to autonomous operation Each isolated site one whose communications have been cut assigns trackers that report to it as if there were no other defenses present The overall defensive assignments are changed the system delays are reduced and the resource allocations will be different The resulting changes in mission success can be studied to ascertain the value of such communications cutting 6 Resource allocation and defensive saturation studies A large attack can saturate the defenses since the number of trackers is limited RJARS does not include track-while-scan radars and thereby produce mission successes that cannot be deduced from one-on-one studies Also the limited number of missiles at a launch site can affect the defensive capability since sites can run out of missiles Mission planners can use RJARS for such studies These are but a few possible applications of RJARS The interested reader can undoubtedly think of ways to apply it to his or her particular field of interest -6- RJARS has limitations that prevent the study of various problems Among these are 1 All aircraft maneuvers have to be preloaded in the scenario Reactive maneuvers such as attempts to evade attacking missiles are not included However reactive maneuvers can be treated in an equivalent fashion by running a scenario ascertaining which defenses interact with the attack and then modifying the flight paths externally The use of flight path generators facilitates this process 2 The airborne warning receivers do not apply priority tables to the detected radar signals so all jammed radars in a frequency band of the jammer receive equal allocations of jammer power Furthermore the warning receivers are assumed to detect the signals as if they were radiated independently Problems of interleaved pulse trains and other high signal density effects are not considered 3 The command and control system for the defense is limited to site and command site up and down interactions with no cross connections between command sites This prevents consideration of large-scale command structures 4 Communications operate in an on-off fashion so studies of effects of communications jamming are limited to circumstances in which jamming is either completely effective or totally ineffective 5 Rain attenuation which can be significant at the higher radar frequencies is not modeled in RJARS so the simulation corresponds to frequencies below 10 GHz or clear weather conditions for frequencies above 10 GHz However IR and optical attenuation are included 6 The phenomena associated with ducting propagation are not included They can cause significant effects on radar propagation over water paths which could be important if RJARS were extended to treat naval surface-to-air operations - 7- 7 As mentioned in the Summary problems of electromagnetic compatibility and electromagnetic interference are not included These may play a very important role in determining if the equipments are actually working in the manner in which they are being simulated It is expected that there will be improvements and additions to RJARS during the coming year The treatment of CW radars will be improved to consider how they handle information differently from pulse radars Clutter for CW seekers will have an improved algorithm for calculating the area from which clutter is received since the present algorithm is both inaccurate and wasteful of computing time array radars will be included Phased Their problems include sector coverage raster or random scan patterns dwell time phenomena and track-while-scan operation Tracking of multiple targets by a single radar use of multiple illuminators and simultaneous control of several SAMs by a single radar will be incorporated over curved irregular ground will be improved for the radars will be incorporated The theory of multipath Electro-optical backup The gun model will be improved and the endgame calculation will include allowance for the probability of kill given a hit for the various aircraft and weapon types The command and control structure will be revamped to provide three-level structure skip echeloning matching operating modes to the tactical situation giving the user a choice of command and control models for the several SAM types and a general improvement in the communications model Not all of these operations may be accomplished We first describe the simulation to depict the sequence of decisions Next an analytical section provides the theoretical basis for the program A user's guide shows how to prepare input files and operate RJARS and a programmer's guide presents programming details and a glossary of the approximately 1100 variables used in RJARS The text that follows is almost entirely mathematical or verbal The author does not think in terms of flow charts and has not used them while building the program However following a reviewer's suggestion a set of flow charts has been included as in Appendix refer to the charts while reading the text The reader can - 9 - II GENERAL PROGRAM DESCRIPTION RJARS is a many-on-many computer simulation involving aircraft radars jamming systems offensive and defensive missiles and overall Hundreds of aircraft and radars may be included control It is implemented either in earth-based or internally referenced coordinates exactly as in JARSM Ref 2 by reading the input data Like all simulation programs it begins These data are contained in two types of files--library files containing equipment parameters and simulation files with the information for a particular run There are nine library files as follows 1 ACLIB Aircraft performance data 2 ACRCS Aircraft cross-section data 3 ARLIB Anti-radiatio m ssiie data 4 IRLIB 5 JMLIB Jammer data 6 MCLUT Tercaii propert 'es 7 RDLIB Radar data 8 SMLIB Surface-to-air missile data 9 WRLIB Warning receiver data ln-u and optical data and nine simulation files 1 SCENA Simulation run parameters 2 ACVIS Aircraft visibility over terrain input 3 ACSGT Air-raft visibility over terrain output 4 TERRA Terrain heights 5 BLUMX Flight paths from BLUE MAX fixed-wing 6 CHAMP Flight paths from CHAMP helicopters 7 RIDGE Ridges as seen by radars input 8 RDRDG Ridges as seen by radars output - 9 DISPL 10 - Graphics display file CAGIS format These files must all be prepared before a run is executed ACSGT RDRDG and DISPL are produced during the simulation Preparation details are given in the user's guide section The library files may be maintained and updated as information is acquired on additional equipments The scenario file SCENA is modified for each run Terrain may be omitted from the run or included in several ways The terrain data may be read in and the visibility between aircraft-radar pairs calculated during a simulation Alternatively a preprocessor mode may be used which traces the paths of the aircraft as specified in the scenario and determines the time intervals for which each aircraft may be visible to each radar The preprocessor output ACSGT may then be moved to the simulation input file ACVIS which then provides visibility intervals for the full simulation be produced by the user from direct reading of maps ACVIS may also The visibility intervals as determined by the terrain are then used to control the simulation If a small terrain region or a relatively small number of aircraft and radars are treated in the simulation and if Monte Carlo operation is not involved then it is usually best to incorporate the terrain effects directly in the simulation For any large problem or if Monte Carlo is included the two-stage preprocessor simulator procedure will almost always be more efficient since the terrainmasking calculation requires considerable computing time and it is most desirable to not have to repeat the lengthy process Multipath and clutter effects involve determining whether the ground from which return is expected is actually visible to the radar This calculation involves determining ridge and reappearance ranges from the radar to the terrain in various directions This is also conveniently performed by a preprocessor since the ridges remain the same throughout the simulation When RJARS is operated in this mode the preprocessor output is placed in a file RDRDG which is then stored under an appropriate name and moved to the working file RIDGE when the configuration is to be treated by the full simulation The RIDGE file - 11 - may be very long if the terrain is complex and there are many radars but this space consideration is overwhelmed by the advantage in running time for a simulation with many Monte Carlo iterations The files RIDGE and ACVIS are prepared by CAGIS in the RAND Military Operations Simulation Facility Since CAGIS is a much more effective program for treating terrain than is RJARS this greatly increases the overall efficiency of the combined systems Each aircraft carries a warning receiver a jammer and a scenarioselected number of air-launched cruise missiles and or anti-radiation missiles The aircraft are organized into groups corresponding to formation flying If an acquisition or track radar locks onto a member of the group all the aircraft in the group will jam the radar Aircraft may split from or join groups under scenario control The defensive system is organized into what we call for lack of a better name a two-level parallel system consisting of sites and command sites Figure 2 depicts a typical configuration forms a site A cluster of radars All types of radars search acquisition and tracking the last with its associated SAM launcher may be represented at a site A site corresponds to the lowest level of field operations Each site is connected via communication links to a command site The communications delays on each link are in the scenario file links may be cut or reconnected These Each command site will perform the assignment of all the defensive resources with which it is linked When the link from a site to a command site is cut the site reverts to autonomous operation and assigns its own resources interaction between command sites There is no Optically aimed weapons such as shoulder-fired IR SAMs and free-standing guns are not included in the command structure but instead receive their information from communications broadcasting The program reads from library and simulation files until all data have been entered If there are any reading errors which cause an end- of-file condition to be reached the program aborts and prints the appropriate error message If no errors have occurred the simulation begins with the aircraft at their initial positions and vector - 12 - CommandComan Site 1 3 20 it Acquisitin2 Track 4 Acquisition 310 Site eSite 34 Search 3 6 Track4 Sfe14 2 Siercof Acquisition Track Site 2 Fig 2-Defensive configuration Track 4 - 13 - velocities and only the search radars and searching optical systems activated RJARS radars can perform a variety of functions They may be purely search radars or may be trackers which can search acquire track and perhaps illuminate the target Also optically guided weapons employ simulated visual observers to perform their search and acquisition functions The changing functions of the individual equipments are followed during the simulation The operation may be conveniently followed by considering a single aircraft There is a specified field of action for the simulation described by maximum and minimum latitudes and longitudes measured with respect to a coordinate origin The aircraft will fly over the terrain and enter this field initially the aircraft may be either inside or outside the field but must be inside the terrain boundaries Equipments may be connected to the command and control system or they may be autonomous Shoulder-fired SAMs and free-standing guns are in the second category Initially all pure search radars and all optical autonomous systems are in search mode the variable RDSTATE is L for the search radars W for the optical systems Also the command system may contain command sites which have no pure search radar at any of their associated sites For such command sites the multifunction radar trackers are in the W state Trackers at other sites are turned off STATE 0 The search radars and optical devices will be scanning and eventually the aircraft will clear the terrain and become visible to some search radar The warning receiver at the aircraft will detect the radar if possible and turn on the jammer if the scenario specifies that this aircraft should jam search radars The jamming technique may be either noise or deciption depending on the characteristics of the radar and the capabilities of the jammer This jamming operation will be deferred until the receiver has an indication that the radar has detected the aircraft thereby avoiding acting as a beacon RJARS is limited to radars Jamming in No jamming is provided for IR or optical systems but flares can be launched against the IR SAMs - 14 - The search radar will receive the reflected signal from the aircraft and if the suitably processed signal exceeds threshold for two of three successive scans it will notify the site that it has a detection This condition which was also used in JARSM should be sufficient to establish target identity The radar will continue to scan and the range bearing and elevation of the aircraft will be determined with errors that depend on aircraft glint and receiver signalto-noise ratio as modified by jamming Each search radar is equipped with a far sidelobe canceller a form of automatic gain control that sets the system threshold so it is not triggered by signals usually jamming which come from directions in the far sidelobes of the radar antenna All detections are probabilistic with a detection probability that is a function of signal-to-noise ratio Radar antenna patterns correspond to elliptical uniformly illuminated dishes with stacked beams for search radars If the radar has information about a particular aircraft and the radar's site is connected to its command site the information will be transmitted to the command site with a delay determined by the communication link At the command site the information will be catalogued and the command site will ascertain whether a tracker has already been assigned to this aircraft The terms tracker and totracking radar are synonyms in this Note If one has nothing further need be done If not the command site examines the data on the aircraft from each radar that has seen it and selects the position information that has the least error to choose the assignment 1 It then looks among its trackers Conditions for assignment are The tracker and its acquisition radar must be alive and unassigned Since either the tracker or the acquisition radar may be killed by an ARM and an acquisition radar may serve several trackers it is necessary to test that both are operating - 2 15 - The aircraft must be visible to both the tracker and acquisition radar 3 The aircraft altitude must be above the minimum and below the maximum altitude of operation for the SAM type associated with the tracker 4 The aircraft must be farther away from the tracker than half the maximum range of the associated SAM This is to provide enough time that the target may be acquired and tracked and the SAM counted down before the aircraft comes closer to the tracker than the minimum operating range of the SAM The condition is too stringent for long-range SAMs 5 The projected flight path of the aircraft must be inside or must pass into the circle around the tracker with radius equal to the maximum range of the SAM 6 It is assumed that the SAM is launched at the earliest time possible including the several system delays and the interception point is calculated This point must be within the maximum range of the SAM 7 Trackers in RJARS have an assigned sector of responsibility For most types especially older vintage the sector is a full circle Certain types including all IR SAMs and guns have limited sectors The target must be within the responsibility sector or be on a heading such that it will enter the sector 8 Among the possibly several trackers that meet the first seven conditions that tracker closest to the present position of the aircraft is assigned If no tracker meets the conditions the program will announce that fact When a tracker is assigned its acquisition radar is turned on at a future time determined by the sum of the decision delay in the command site and the communications delay in the downlink between the command site and the site For a multifunction radar the tracker and acquisition radar are the same equipment and the change is indicated by setting the variable RDSTATE to 'A' If the assigned equipment is an IR SAM launcher certain types of IR systems are under centralized control - 16 - rather than autonomous it goes directly into the track state--RDSTATE 'Q'--and begins seeking the target If the communications link between a site and its command site is cut the assignment operation proceeds as above but only those search acquisition and track radars associated with the site may participate The decision and up-and-down communications delays disappear The autonomous IR SAMs and guns receive their information in a different manner Initially they are in the W or searching state scanning across their sector of responsibility using eyeballs perhaps aided by binoculars An algorithm gives the detection probability in terms of the optical contrast at the viewer If one detects it goes immediately to the A state in which it uses the algorithm with a stronger criterion recognition rather than simple detection and instead of scanning stares in the apparent direction of the target it recognizes the target it goes into track If Meanwhile the command sites which have been observing the battlefield will broadcast the information on target position for each radar-detected aircraft This broadcast information is received at all sites and used to cue the optical searchers to a narrower sector so they have a better detection probability The probability of receiving correct information at a site is at the moment set to unity This was done because a survey of existing HF and UHF radio equipments on the possible sides of the simulated combat indicated that the range of successful transmission of information usually exceeded the dimensions of the RJARS combat field It is expected that radio propagation will be studied to provide message probability for possible future versions of RJARS The broadcast from each command site continues as long as that command site has information on that aircraft but a site need be cued only once When the acquisition radar is turned on it behaves like a search radar but only collects information on its assigned target Those aircraft in the group associated with the target that detect the acquisition radar and are designated by the scenario as acquisition jammers will jam the acquisition radar For the acquisition radar to - 17 - establish acquisition and turn on the tracker it must detect the aircraft on three out of five successive scans with no two consecutive failures to detect in the sequence This requirement permits the acquisition radar to provide good initial information to the tracker Designating detection by D and nondetection by N the only sequences of successive scans that can establish acquisition are DDD DDND DNDD and DNDND If none of these patterns occurs in a time specified as a parameter of the radar type the acquisition radar drops acquisition and returns the aircraft to the assignment procedure Other reasons for dropping acquisition that have been implemented are 1 Tracker or acquisition radar killed by an ARM 2 Aircraft shot down by a SAM from another site 3 Aircraft outbound and nominal interception point outside the maximum range of the SAM before acquisition occurs 4 Tracker reassigned There is a priority choice among aircraft and the current assignment may be overridden 5 Aircraft leaves the field of view of the radar usually because of terrain masking If the tracker is turned on it begins to track the target aircraft with errors determined by servo acceleration lag target glint and signal-to-noise ratio as modified by jamming The tracker may be susceptible to range deception angle deception or both If the jammer on the target aircraft or members of its group are designated to jam trackers and if it is capable of producing the desired jamming technique it employs the tactic appropriate to the tracker Otherwise random noise is radiated Multipath and clutter effects are now included in RJARS effects are calculated for search and track radars Multipath Clutter effects are calculated for search and track radars pulse doppler seekers and CW seekers Most of the multipath and clutter treatment is taken from ESAMS Ref 6 - 18 - The aircraft may be carrying ARMs These are designated by the scenario as preprogrammed in which case they may be launched only at a specified radar or opportunistic for which they may be launched at trackers which are operating against the indicated aircraft Each ARM has a specified operating frequency band and a minimum and maximum range and the target tracker must be within the frequency and range limits for launch to take place Once an ARM is launched it flies in a lofted trajectory at constant velocity toward its target If the radar ceases to transmit the ARM will continue its flight for a specified time with the kill probability reducing linearly to zero during that time The alternate condition in which the ARM diverts to another target is not implemented in RJARS a limitation of the simulation Otherwise it will fly to the target and perform a random draw against a probability of kill to determine the outcome of the attack With the tracker providing information about the path of the aircraft the SAM system will determine when a SAM should be launched The requirement for launch is that the position of intersection of the extrapolated path of the aircraft and the straight line path of the SAM when flown at the proper heading should lie between the range of the SAM at booster cutoff and the maximum range of the SAM All SAMs are treated as four-stage devices composed of an initial unguided booster an unpowered coast for most SAMs the duration of the coast is zero a powered and guided sustainer and an unpowered guided coasting stage After a random draw to determine launch success the SAM is launched propelled by calculating thrust and drag accelerations and guided either by a variation of lead pursuit guidance in which the SAM heading is pointed toward the projected aircraft position or by proportional navigation each with a lag corresponding to the missile dynamics When the SAM reaches its calculated minimum distance from the target which calculation includes the errors in the radar guidance information it determines a nominal miss distance by adding an error in an arbitrary direction corresponding to the error in the SAM guidance system point of closest approach is compared to the oriented aircraft This The aircraft is taken to be an ellipsoidal fuselage with elliptical wings - 19 If the closest approach point is within the aircraft corrsponding to an actual hit the kill probability is taken to be unity This is a reasonable assumption for large warhead weapons but is too favorable to the defense for small warhead weapons or artillery If the aircraft is missed but the weapon contains a proximity fuse shoulder-fired IR SAMs and all guns are assumed to have contact fuses others proximity fuses the SAM kill probability is taken to be constant for a miss distance less then a specified value the value of the constant is the SAM warhead reliability and to drop linearly with miss distance to zero at a value large enough that the kill probability should be negligible Another random draw determines the outcome of this endgame If the aircraft is killed it is removed from the simulation and the tracker and SAM revert to the available state If the aircraft survives the equivalent of shoot-look-shoot makes the SAM start counting down again The process is contii ued until the aircraft is killed or escapes from the effective range case the assignment if the tracker-SAM combination In the latter 6 tem takes over The term SM may include anti-aircraft artillery gun as a special case of a SAM RJARS treats a The propulsion takes place only in a very short booster stage chosen to give the projectile its correct initial velocity and the trajectory thereafter is unpowered constant mass and unguided drag is still simulated The launch calculation is modified to determine the shell trajectory and find the proper aiming direction Air density variation and gravity drop are included The kill probability is the kill probability per burst not per bullet In other respects the simulation is the same Radar-guided SAMs may obtain their guidance information directly from the tracker via data link corresponding to command guidance or may use a semiactive system in which an illuminator located at the tracker shines on the target and the reflected signal is received at the seeker mounted on the missile is turned on at launch time For a semiactive system the illuminator - 20 - While all these complex operations are going on in the defensive system the aircraft is performing maneuvers of its own Under the control of the scenario it can accelerate climb or turn each at a specified rate to a new value of velocity altitude or heading Jammers can be turned on and off by the scenario as well as by the automatically operating warning receiver groups It can split from or join ARMs can be launched as can air-launched cruise missiles The latter are treated by the simulation as additional aircraft each with its appropriate parameters and flight maneuvers The cruise missiles are visible to the radar only after they have been launched Maneuver commands should not be given to cruise missiles while they are on board their respective carriers The aircraft may also tow jamming decoys The aircraft will normally have a destination within the interaction field and will then turn and proceed homeward This change triggers the defensive system to lower the priority on that aircraft so if it is being tracked and no SAM has yet been launched the tracker is included in the assignment pool if an incoming aircraft is detected RJARS grinds through the simulation as described above until either the end of the simulation time is reached or all aircraft are shot down Output is provided at selectable time intervals for the aircraft radar and missile status positions etc At the end of the run summaries are printed showing the detections of each search radar against each aircraft tracking times of assignment acquisition and tracking SAM and ARM launches and outcomes and an overall box score RJARS can perform Monte Carlo operations If a number of runs is specified at the end of each run until the last all the scenario parameters except the random number generator will be returned to their initial values The run will then be repeated but the outcomes of the various random draws can be expected to be different Statistics on the runs can be compiled RJARS now includes a graphics calculation This is provided as a file in CAGIS format and is the only nonportable part of RJARS With the graphics the terrain and defenses may be depicted on the screen along with the aircraft SAM flight paths and their interactions As - 21 an aircraft progresses along its path it is initially in black The path color changes to gray when a searcher detects the aircraft to blue when a tracker is in acquisition to yellow when a tracker is in track and to orange when a SAM or shell has been launched red SAM paths are in An endgame miss is a small red star an endgame kill is a large red star Icons are used for the defenses to indicate the type of radar SAM or gun Targets for the aircraft may also be shown Iterations may be presented in sequence The paths may be laid down all at once or the flights may be time-stepped The latter is usually much more descriptive The graphics operation is an RJARS postprocessor for which the data file is prepared during the RJARS run and the graphics program may be run at any time The printed output from RJARS is extensive and we have usually found it sufficient for our purposes The graphics are useful for determining general characteristics of a particular simulation run This completes the general program description We shall next present the analysis and show the development of the several program modules RJARS contains 11 updating modules 1 UPDCK System clock 2 UPDAC Aircraft positions and maneuvers 3 UPDTR Over-terrain visibility 4 UPDRS Search radars 5 UPDSI Sites and assignment of trackers 6 UPDRT Tracking radars 7 UPDAR Anti-radiation missiles 8 UPDSM Surface-to-air missiles 9 UPDWR Warning receivers 10 OUTPUT Summary outputs 11 UPDMC Monte Carlo These will be discussed in detail - 22 - N-2727-AF Ref 3 contains an appendix listing of the PL-I program The C program is inherently much longer and with the many added phenomena the listing has grown too long to be practical Therefore the Note has undergone an appendectomy followed by a resection a new and much shorter appendix containing flow charts - 23 - III A UPDCK--SYSTEM ANALYSIS SECTION CLOCK The system clock is updated at each time step generally used a time step of 2 5 seconds The author has This is shorter than the scan period of most search radars but is such that the aircraft will move 1400 feet Mach 5 to 5600 feet Mach 2 during the step distances large enough to be observed by the system Since the SAMs require much better position measurement the time step is subdivided and the aircraft position interpolated when a SAM is in flight toward the aircraft The clock keeps track of the simulation time and of the number of surviving aircraft If the end of simulation time maximum 9999 seconds is reached or if all the aircraft have been shot down the clock signals the main program to terminate this simulation run print the summaries and continue to the next Monte Carlo sequence if necessary B UPDAC--AIRCRAFT POSITION AND MANEUVERS In the subroutine UPDAC the aircraft position is updated and any scenario-required maneuvers are performed If terrain effects are included VIS 2 or 3 the aircraft input altitude and any subsequent climb maneuvers are specified with respect to the terrain so a constant altitude value would correspond to terrain following The flight path may be presented in two ways either by a sequence of maneuver commands like the previous treatments or by the prescription of an external flight path generator BLUE MAX or CHAMP The maneuver sequence technique will be described first then the flight path generator technique 24 - 1 Position Updating and Maneuvers The position updating used in JARSM has been improved in RJARS In JARSM the aircraft latitude and longitude are updated at the beginning of UPDAC using the values of velocity and heading valid at the previous time step If a maneuver is called or in progress the velocity altitude or heading is then updated using the value of acceleration climb rate or turn rate as appropriate further updated However the position is not If for example an acceleration of 2 g 64 fps 2 is in progress in an interval of 2 5 seconds the aircraft will travel an additional 200 feet This may not be important to radar detection but is far too much error for SAM guidance position updating to second order Consequently RJARS carries In addition climb maneuvers include pitching to the correct attitude The aircraft velocity vector in RJARS has magnitude ACVEL pitch ACPITCH horizontal 0 and heading ACHDG zero northbound positive clockwise Simplifying these to V P and H the northward eastward and vertical components of velocity are VN V cosP cosH la VE V cosP sinH lb Vz V sinP 1c Differentiating these gives the rectangular components of acceleration where a dot above a variable denotes its time derivative VN V cosP-V- P sinP cosH-V H cosP sinH VN V cos P- V P sin P sin H V Hf cosP cosH Vz s in P V P cosP 2a 2b 2c In JARSM and also in RJARS the motion of the aircraft is straight and level unless a maneuver is called A maneuver may be an acceleration for which dV dt is constant a horizontal turn for which - 25 - dH dt is constant a climb for which Vz is constant or a pitch for which the pitch rate dP dt is constant The scenario specifies the maneuvers in terms of a starting time T O which need not be a multiple of the time step DT a maneuver rate acceleration turn rate pitch rate or climb rate and a final value for velocity heading pitch or altitude The duration of the maneuver is the quotient of the difference between final and initial values and the maneuver rate and usually includes several time steps The time available for maneuver during each time step is designated VARS in the program VAR5 is one of many dummy calculation variables and has other meanings in different parts of the program At the time step immediately after initiation of the maneuver VAR5 T - TO intermediate time steps VAR5 DT For For the final time step VAR5 T0 maneuver duration - T where T is the simulation time at the last time step before the end of the maneuver The maximum pitch acceleration up or down and the maximum turn acceleration are given in g's for each aircraft type in ACLIB If the turn rate or pitch rate specified in the maneuver leads to an angular acceleration that exceeds the maximum it is replaced by the limiting vrlue A climb maneuver is rather complex The specified input parameters are the climb rate and the final altitude The rate determines the pitch during the steady climb part of the maneuver If the climb is upward a pitch maneuver to the steady pitch at the maximum upward pitch rate PITACUP begins the climb and a downward maneuver to level flight at the maximum downward pitch rate PITACDN completes the maneuver Between these the aircraft climbs at a constant rate The time to initiate the downward maneuver is calculated before the climb begins For descents the pitch maneuvers are first down then up If the difference in altitude is so small that there is no time for a steady climb at the indicated climb rate the up and down pitch maneuvers are matched to the altitude difference 26 - Occasionally the maneuvers will be so small that they should be completed in less than one time step RJARS checks such details and modifies the values of VAR5 see above accordingly For example the first pitch maneuver of a climb may take less than one time step RJARS will complete the pitch maneuver bring the aircraft to the proper attitude velocity and position and initiate the climb maneuver with the correct value of VARS These techniques are applied to all maneuvers At the beginning of UPDAC at every time step the horizontal components of position are updated by ALAT V DT cosP cosH 3a ALONG V DT cosP sinH 3b where A denotes change of During an acceleration maneuver the velocity and horizontal components of position are updated by AV V VAR5 ALAT 5 V VAR 4a 5 2 cosH cosP ALONG 5 V VAR 5 2 sinH CosP 4b 4c During a pitch maneuver the pitch and components of position are updated by AP P VAR 5 5a ALAT - 5 V VAR5 2 cos H sin P 5b ALONG - 5 V VAR 5 2 sinH sinP 5c AALT 5 V VAR 5 2 CosP 5d During a turn maneuver the heading and horizontal components of position are updated by - 27 - 6a AH H VAR5 ALAT - 5 V 1H VAR 5 2 cos P sin H ALONG 5 V H VAR 5 2 cos P cos H 6b 6c During a climb maneuver the altitude is updated by AALT Vz VAR 5 7 These formulas hold for the increments in velocity vector and position vector during the maneuver An additional correction is required during the final time step to take account of the fact that after the maneuver is completed the velocity vector continues at its commanded value rather than its value at the beginning of the time step This correction adds to the latitude change during the final step of acceleration ALAT V VAR5 DT-VAR5 cosH cosP 8 and corresponding terms for the other position terms A note on units is in order system of English units altitude in feet Latitude and longitude are in nautical miles Horizontal and total velocity are in knots vertical velocity in feet per second seconds Both JARSM and RJARS employ a mixed All angles are in degrees and all times in As a result factors of 6080 feet per nautical mile 3600 seconds per hour and DR 7 180 radians per degree are scattered all through RJARS and anyone who wishes to make modifications must be wary - 2 28 - Flight Path Generators RJARS is prepared to accept input flight data from either the fixed- wing flight path generator BLUE MAX or the helicopter flight path generator CHAMP They work in basically the same manner The CAGIS mapping program is used to set up the terrain over which the path is to be flown The user selects a starting point then a next point along the path In the terrain following mode the path generator will attempt to fly from one point to the next at constant altitude above the terrain going directly over obstacles In the terrain avoidance mode he will look ahead and either go over or around the obstacle The aircraft dynamics are used to find the actual path under the conditions indicated The path is continued through an appropriate number of points to the destination and return The use of these path generators is strongly dependent on the ability of the simulator pilot who must understand both the dynamics of the aircraft and the tactics that may be required for the mission lest he crash or overstress on route For example flying a helicopter five feet off the ground through tree at a speed of 150 knots is permitted by the flight path generator but is unlikely in real life These flight path generators whose operation has many arcane qualities have proved extremely valuable The output of the flight path generator is a file that includes for each path an identification number a time step and the aircraft position vector latitude longitude and altitude its velocity vector velocity pitch and heading and its attitude vector nose pitch bank and yaw For helicopters it also contains a hiding parameter 0 if fully exposed 1 if only rotor exposed 2 if hiding For the special case of tilting rotor vehicles the tilt angle is presented There may be several flight paths used in the simulation RJARS employs the convention that helicopter flight paths obtained from CHAMP have an identification number greater than 100 apply the same convention Helicopter types The flight paths may have different durations and different initial delays The primary purpose of the initial delay is to permit several aircraft to be flown down the same path without having to construct new visibility tables If the - 29 - simulation time exceeds the duration of the path RJARS uses the PITCH maneuver to bring the aircraft to level flight then continues the path straight and level over the terrain with the ve 'zity and heading of the last point on the path Similarly for times before the initiation of the delayed path RJARS extrapolates the path backwards from the initial point straight and level If a path goes off the terrain the aircraft is removed from the simulation with the announcement that it has been TERMINATED WITH EXTREME PREJUDICE This is to avoid trying to calculate height above nonexistent terrain which will go outside the limits of the terrain array 3 Nonpositional Maneuvers In the flight maneuvers section of the scenario each maneuver for each aircraft is written as a single line containing four values--the time of the maneuver a character expression five or fewer letters identifying the maneuver type and two parameters X and Y that give the maneuver specifics The maneuvers for a specified aircraft are sequenced by the maneuver time several maneuvers may begin at the same time and the last maneuver for each aircraft must have the time 9999 The sets of maneuvers for each aircraft are then sequenced by aircraft number not specifically included in SCENA so first all the maneuvers for aircraft 1 appear then all those for aircraft 2 up to the last aircraft If an aircraft has no maneuvers an unlikely event the 9999 line must still appear In addition the flight maneuvers section includes a dummy aircraft NAC 1 where NAC is the number of aircraft This dummy which must be present represents connection and cutting of the communications systems and was placed here because it has the same input pattern as flight maneuvers It is discussed in the command section UPDSI Besides the positional maneuvers ACCEL CLIMB PITCH and TURN the aircraft has several mission-related maneuvers 1 ON Those are Turns the aircraft jammer on Used only - 30 - if at some earlier time the jammer has been turned off 2 OFF Turns the aircraft jammer off Used if the scenario designer wishes to maintain radio silence during a point of the flight or to simulate jammer failure 3 HOME Flag to indicate the aircraft has reached its destination and is returning to base Acts as trigger on the defensive system to reduce priority 4 SPLIT The aircraft splits from its group parameter X and will jam only those radars involved with itself 5 JOIN The aircraft joins a group parameter X and will jam all radars involved with the group SPLIT and JOIN simulate formation flying and flight command operations 6 VIS Aircraft becomes visible to a radar X and will be until a time Y Used to simulate terrain effects when operating in the terrain not included mode VIS 0 7 BLANK Used for air-launched cruise missiles ALCM ALCM is on board aircraft X and is invisible to all radars After a missile has been placed aboard a carrier aircraft it will maintain the position of its carrier Maneuvers should not be given to a cruise - 31 - missile while it is blanked 8 SEP Used for ALCMs Aircraft X has launched the ALCM which can now be observed by radars 9 DECOY Release a towed decoy jammer to a backward displacement X ft Jammer on decoy is of type Y 10 ATTK Attack command Aircraft or ALCM attacks its target at latitude X and longitude Y If information about kill probability of weapons is available a kill maneuver command can be added 11 BLUMX Fixed-wing aircraft is to follow BLUE MAX flight path X with time delay Y This is given with TIME 0 The flight path previously read in is associated with the aircraft which will follow the stored flight path values for position velocity vector and attitude 12 CHAMP Helicopter follows CHAMP flight path X with time delay Y See BLUMX The hiding state of the helicopter is included in the data 13 HIDE Helicopter goes into hiding at altitude X above ground 14 SENSE Helicopter exposes its sensor if any at altitude X above ground 15 ROTON Helicopter exposes its rotor only 16 POPUP Helicopter climbs vertically to altitude above - 32 - ground X with vertical velocity Y fps 17 BLINK Establish aircraft X as partner using blink jamming technique Y 18 BLKPR Set blink jamming period Y with partner X In the actual C program the names of the maneuvers are supplemented with sufficient x characters to form a five-character word RJARS is capable of handling five types of jamming decoys decoy is itself an aircraft of type 13 The The scenario specifies that there are NDECOY decoys on each carrier aircraft where NDECOY may be zero Only one decoy per aircraft is towed at a given time At the beginning of the simulation a decoy is deployed via the maneuver DECOY see above If the decoy is killed by a SAM that has been fooled into attacking the decoy instead of the carrier aircraft another decoy will be deployed until there are none left The jamming techniques available to the decoys will be discussed under tracking radars The position of the aircraft is printed out at intervals determined by a multiplier IPA every 10 seconds If DT 2 5 IPA 4 the position will be printed If a position maneuver is in progress the maneuver time and current value of velocity heading or altitude is printed at each time step during the maneuver Mission maneuvers are printed at their time of occurrence C UPDTR--OVER-TERRAIN VISIBILITY The manner in which terrain is treated by RJARS is controlled by the variable VIS It may take on five values with the following meanings I VIS 0 No terrain smooth earth 2 Visibility during simulation VIS I read from ACVIS file - 3 VIS 2 33 - Preparation of visibility file ACSGT from aircraft flight paths radar positions and TERRA file 4 VIS 3 Visibility over terrain calculated during simulation using TERRA file 5 VIS 4 Calculate the ridges for the radar laydown If VIS 0 the visibility calculations and over-the-horizon determination are performed using a smooth spherical earth with radius equal to 4 3 of the earth radius a factor that takes into account the average effects of refraction on the radar line of sight For the other cases the terrain is used to control the visibility between aircraft-radar pairs It is simplest to first explain the calculations when VIS 3 The input file TERRA contains the locations and heights of the many terrain elements contained in the field of action of the simulation The locations may be in RJARS rectangular coordinates or may be global values in the form of degrees and fractions of degrees not degrees minutes and seconds The locations and heights may be derived from maps from preexisting terrain files or by using CAGIS As presently designed two terrain elements are stored on each line of TERRA If the field of action is 50 miles by 50 miles and the resolution element is 1 4 mile there will be 40 000 elements occupying 20 000 lines so evidently TERRA can be very large The terrain field and the aircraft flight paths must be so related that no aircraft ever comes into a border element of the terrain As the simulation proceeds the aircraft are flown along their prescribed paths At each time step the azimuth and elevation of the line of sight from each radar to each aircraft is calculated This line of sight will pass over several terrain elements as it extends to the - 34 - range of the aircraft Beginning at the radar the distance along the line of sight is incremented in steps equal to half the length of the diagonal of a terrain element miles or degrees All terrain elements are the same size At each point the height of the line of sight above sea level on the spherical earth is calculated by first finding the height above the plane surface that is tangent to the radius vector from the center of the earth to the radar then lowering by the square of the ground range divided by twice the modified earth radius The height-finding subroutine ZTERN is called to find the height of the terrain at the point beneath the calculation point If the terrain height exceeds the test point height by ten feet an arbitrary margin included to provide some effect of aircraft size the line of sight is masked It is assumed in the calculations that the field of action is sufficiently small compared to the modified earth radius 4586 nm that only first-order terms in the ratio need be kept This should be valid at least for dimensions of 200 nm Each line of sight is tested along its length to determine masking If a line of sight is masked that aircraft-radar pair is excluded from the simulation calculations Memory is provided for acquisition or tracking radars which are not treated as masked until three scans or settling times have elapsed The modes VIS 1 and VIS 2 are complementary If VIS 1 the file ACVIS is read to provide a list of times for each aircraft-radar pair during which they are mutually visible The mode VIS 2 creates the file ACSGT equivalent to ACVIS and thus acts as a preprocessor for VIS 1 With VIS 2 the aircraft are flown along their paths but no radars or missiles are activated At each time step the masking calculations are performed as described assumed masked Initially all pairs are A visibility matrix with three arguments the aircraft-radar pair and counter VISKEY for that pair is initialized so all on-times are 9999 and all off-times are zero If a line of sight becomes unmasked the counter VISKEY for that pair is incremented the - 35 - on-time is stored and the off-time is set to 9999 If at a later time the line becomes masked again the off-time is stored is continued to the end of the simulation This procedure Then the visibility matrix is read into the file ACSGT in order of increasing on-time actually nondecreasing on-time since several pairs may have the same on-time A terminator line with an on-time of 9999 is automatically added to the file since the input file ACVIS see below always reads one line further than the last line whose on-time equals the current time If VIS 2 has been run the terrain may be included in the simulation by running VIS 1 The file ACSGT should be copied to the input file ACVIS Then when RJARS is run the visibility data for each pair will be read in at the time that visibility begins The simulation proceeds with the aircraft-radar horizon limits determined by the visibility data from the file If ACVIS is prepared as shown all on times will be multiples of the time step It is also possible to prepare ACVIS directly from maps or CAGIS if the terrain field is small or smooth In this situation the on times may be arbitrary At RAND ACVIS is normally prepared by CAGIS so the mode VIS 2 is not required However users of RJARS who do not have CAGIS available or who are not concerned with a specific terrain region can use VIS 2 to calculate visibility without the intercession of CAGIS If only a single run is desired or if the terrain field is small it is reasonable to use VIS 3 In most cases if many runs are desired or different jammers or radars are to be considered the preprocessor VIS 2 should be employed so that the later runs with VIS 1 do not have to calculate the terrain masking effects The mode VIS 4 is used to calculate ridges for clutter or optical systems This is normally performed in CAGIS but RJARS also has the requisite capability For each ground equipment calculations are performed at a set of angles determined by the parameter nrdgangle number of ridge angles defaulted to 37 corresponding to an angular spacing of 10 degrees Along each direction distance is stepped in small units and the visibility to the radar of the ground at each point - 36 - is ascertained Because of the variable terrain height the ground may go in and out of visibility Each time it goes out of visibility the range and depression angle are stored tuie When it reappears at previous depression angle the range is stored continued out to the terrain boundary The process is The number of ridges in any direction is of course unknown at the beginning of the simLlaLion Multipath and clutter effect calculations require a knowledge of whether the ground is visible to the radar or seeker Optical equipments use ridge data to determine if the target is seen against a sky or ground background The ridge data file RIDGE is required if any of the flags ICLUT clutter included IMULT multipath included or IOPT optical equipment in use is set The read-in scans the RIDGE file twice the first time to determine the number of ridges in each direction the second time to dynamically allocate space and read the ridge data If CAGIS is available it provides the ridge data file for a given defensive laydown first run RJARS with VIS 4 If not The ridge data are stored in the file RDRDG which should be transferred to a permanent location When the ridge data are required for the simulation they should be copied to the file RIDGE which is the data input file for use of ridge data Thus VIS 4 is a preprocessor for RJARS and need be run only once for each defensive laydown Again like VIS 2 it should be run before using VIS 1 for the actual simulation D UPDRS--UPDATE SEARCH RADARS In RJARS radars are divided into six categories identified by a four-character code Each radar is The first character may be L long- range search H height finding A acquisition T track Q IR or G gun The letter Q is used rather than I because I is used for the illuminator state for semiactive missile launchers The heightfinders' peculiar scanning and nodding motion has not been implemented in RJARS so an option HF has been included in the scenario then the height-finders are excluded from calculation If HF N Also no height- - 37 - finders need be included in the scenario If height-finder-type radars are included they are treated just like long-range search radars The radar theory used in RJARS is based on Refs 4 and 5 The data pertaining to each radar type are contained in file RDLIB See the user's section for instructions on preparing RDLIB The scenario contains the location type and site identification of each radar The radars may be in any order in the scenario There are many variables that are associated only with search radars and many others including all SAM variables that are associated only with trackers The PL-I version of RJARS carries the radars in two lists one for trackers and one for all others thus reducing the required working space considerably Because of the multifunction radar concept and the dynamic allocation this double listing has not been incorporated into the C version It probably will be in the future After the radar data have been entered certain calculations are performed to set radar variables that are retained throughout the simulation The search radars are initially turned on and are oriented in random directions The frequency of each radar which is specified by RDLIB as being between an upper and lower bound is set to a random value within that frequency range The search radars then begin scanning clockwise at their specified scan rates and will continue to scan unless they are killed by an ARM Optical systems search a sector rather than spinning The subroutine SECTSCAN moves the direction of observation in a sawtooth pattern across the sector of responsibility the lower scan limit Initially viewers are at The subroutine INBEAM determines if the sawtooth scan has passed over the target during the time step 1 Signal and Jamming Power Analysis The signal power received from the aircraft by the radar at the time when the main beam of the radar passes over the aircraft is - 38 ERP R GR C2 OT 9 4n F R RRT The variables in this equation are ERP R Effective radiated power of the radar GR Radar antenna gain on axis LR Losses in the radar receiving system C Velocity of light aT Scattering cross-section of the target FR Radar frequency RRT Range from the radar to the target This may be rewritten in the form S RPROD R GT RRT 10 where aT is in square meters RRT in nautical miles and the multiplier RPROD held through the simulation is 8 RPROD 2 32 10- ERP W G L F MHZ 2 where the subscript R is implied Equation 9 represents free space propagation with no additional attenuation of the signal Rain attenuation which can be significant at the higher radar frequencies is not modeled in RJARS so the simulation corresponds to frequencies below 10 GHz or clear weather conditions for frequencies above 10 GHz In the absence of jamming the noise power in the receiver is 11 39 - 12a MJS R k T NF R BW R 4 10- 14 BW MHZ 12b where k is Boltzmann's constant T the receiver temperature NF the receiver noise figure and BW the receiver band width In going from 12a to 12b the effective receiver temperature T'NF has been set to 3000 degrees Kelvin receiver The actual temperature varies from receiver to However for any well-designed radar the signal is large compared to receiver noise when the target is within the operating range of the system The receiver noise provides a floor for the undesired signal amplitude when the radar is jammed but any effective jammer will produce at the radar a power large compared to receiver noise Thus the receiver noise temperature which in any case does not vary over a wide range 600 degrees Kelvin is very good 10000 degrees Kelvin is very poor is not a critical parameter The signal will be processed by the receiver which will integrate over the number of pulses received from the target The receiver threshold will be set to a level determined by the false alarm rate In JARSM this threshold setting was an input parameter which had to be set by the scenario writer In RJARS we have used the theory of detection for search radars Refs 4 5 and fitted the curve for probability of detection 0 5 false alarm rate 10 -6 Ref 4 page 2 22 Fig 9 by the expr - MDS dB 11 2 - 8 45 logIoN 0 75 logoN 2 13 where N the number of pulses integrated N PRF R SCN R HB R 360 14 If the false alarm rate were raised to 10 -4 the threshold MDS would be - 40 - lowered by 1 5 dB the constant 11 2 in equation 13 would become 9 7 This is not a significant variation In Eq 14 PRF is the radar pulse repetition frequency in pulses per second SCN is the radar scan period in seconds and HB is the horizontal beamwidth between half-power points of the radar antenna The receiver is set at a threshold MDS dB above the noise floor MJS When jamming is present the power received from each jammer is ERP j GR LR C 2 Lp BW R EFF R SDL 1 4C 2 FR RR BW i 15 where the added variables are ERP J Effective radiated power of the jammer GJR Gain of the jammer antenna in the direction of the radar LpPLoss due to polarization difference between radar and jammer--usually 3 dB corresponding to linear polarization of the radar and circular polarization of the jammer SDL JR Sidelobe attenuation of the radar in the direction of the jammer relative to main beam gain RRJ Distance from radar to jammer BW J Bandwidth over which the jammer is radiating noise EFF JR If the jammer is employing deceptive tactics - 41 - EFF JR BW J BW R1 so all the jammer power is in the radar receiver band Otherwise EFF JR 1 Many airborne jammers use multiple antennas to achieve coverage without scanning direction Each antenna provides coverage in a particular The combined pattern is approximated by a rosette antenna pattern which contains JMNLEAF lobes All lobes have the beamwidths JMNHB and JMNVB in the horizontal and vertical planes and are offset by an angle JMDIP in the vertical plane The first lobe is offset from the forward direction by an angle JMBS and the succeeding lobes are centered on directions displaced from the first by multiples of an angle JMPHIN 360 JMNLEAF The antenna gain is calculated from this rosette pattern Among the radar's input parameters is the jamming tactic to which it is susceptible as discussed in the general simulation description Since all deception techniques involve repeating the transmitted signal thereby matching the band width the indicated effectiveness factor is included in the jamming power RJARS has additional capabilities for determining jamming effectiveness which will be discussed under tracking radars To calculate the sidelobe level the antenna pattern must be known In RJARS the basic antenna pattern is an elliptical pencil beam The sidelobe level SDL is calculated by the subroutine ANTPAT1 which has as arguments the azimuth angle off axis PHI the elevation angle off axis THETA the horizontal and vertical beamwidths between half-power points HB and VB and the backlobe level BL The elliptical scaled off-axis angle X is given by sinCHETA 2 c sin PHI 12112 In terms of X the pattern is gaussian for X less than 1 2 constant 16 - 42 - from 1 2 to 2 filling in the first null then follows the envelope of the many-lobed pattern out to the backlobe level SDL min 12 041 X 2 17 526 min 1O 25 log1o X BL In detail 17a X 2 17b X 2 Equation 17b is the standard pattern used by the CCIR International Radio Consultative Committee to characterize the sidelobe pattern of communications satellite antennas which are similar to radar antennas The parameters HB VB and BL are inputs from RDLIB The far sidelobe level BL is often about 30-35 dB but careful sidelobe design may make it lower This pattern corresponds to a single pencil beam However many search radars use multiple beams stacking them in elevation to achieve sharper vertical resolution while maintaining broad coverage Hence search radar patterns are calculated by a pattern function ANTPATS which combines the patterns of NSTACK individual beams each having the vertical beamwidth NVB with the first elevated upward by a half beamwidth and the successive lobes having centers separated by one beamwidth Above the highest lobe the pattern is completed by a cosecant square function 2 The value of NSTACK is stored in RDLIB Jamming Sequence The first operation in UPDRS is to determine if jamming is present and if it is to set the backlobe canceller and present the strobe widths The backlobe canceller is a practical device a low-gain antenna slaved to the high-gain radar antenna Jammers that are at angles far from the antenna boresight angle will be enhanced in the receiver associated with the low-gain antenna relative to the highgain antenna and thereby identified The gain of the main receiver is set so these signals do not appear on the display - 43 - Each aircraft keeps a running identification of which radars it is jamming in each of the frequency bands of the jammer This information is used to determine the power received at the radar The antenna direction is updated at each time step by adding to it a value RSANTCH the angle through which the radar turns in a time step A subroutine LINSGHT which is used in many places in RJARS calculates the range elevation and azimuth from the radar to the target and if terrain is not included in the simulation VIS 0 determines if the aircraft is beyond the horizon to the radar The aircraft sequence is run through twice The first time the power from those jammers that are in the backlobe of the radar is summed and the resulting total used to get the receiver threshold The second time through the factor by which the jammer power exceeds the receiver threshold is determined and the antenna pattern formula Eq 17 is inverted to find the angle at which the jamming signal level blends into background This is the strobe width which is then printed out A scenario-set parameter IP controls the printout rate each IP'th time step will be printed 3 Detection Probability Target detection probability is the next quantity calculated set of aircraft is run through again The It is determined at each step whether the aircraft is within the effective field of view of the radar Here effective means that the aircraft is within the physical horizon of the radar the flag RDACOH marks this and whether it is within the maximum range at which the aircraft could be detected by the radar This latter range is the product of the radar's maximum range against a 1-m2 target an input parameter and the fourth root of the nose-on cross-section of the aircraft in square meters For the special case of low-observable aircraft marked by the setting of the flag ILOBS in the scenario the cross section in the horizontal plane averaged over azimuth is used instead of the nose-on cross section This modification was installed when it was found that RJARS was waiting too long for low-observable aircraft with very low nose-on cross section - 44 - even when they were being observed from another direction If the aircraft is within the effective field of view it is tested to see if the main beam of the radar passed over the aircraft during the last time step If it did the signal power and jamming power are calculated and the probability of detection is found RJARS radars are all equipped with mcving target indicators MTI The radial component of target velocity is calculated yielding the doppler frequency A two-stage delay line simulator provides attenuation proportional to the fourth power of the doppler frequency when it is below the doppler filter threshold determined by the pulse repetition rate of the radar The clutter signal reduction for search radars is limited by scanning noise which is proportional to the square of the number of pulses on the target Pulse doppler systems with semiactive seekers may use a very high PRF For such systems eight times the width of the doppler filter is used for the critical frequency instead of the PRF 3a This appears to closely match practice Radar Cross Section The radar cross-section treatment in RJARS is more extensive than in JARSM The variable NDOF in the scenario determines whether the aircraft attitude is calculated If NDOF 3 no attitude information the radar cross section is stored as a function of aspect angle only If NDOF 5 attitude information the cross section is stored as a function of both defining angles of the line of sight from the radar to the oriented aircraft the cross section data Further RJARS permits variable resolution for Two numbers ACRCSAZRES and ACRCSELRES which may differ are stored in the data file ACRCS for each aircraft and the data are stored at that angular resolution The units of radar cross section are dBsm decibels with respect to one square meter The radar cross section of a helicopter is calculated in two ways associated with its motion over the ground and with the spinning rotor As mentioned before the helicopter consists of a body a rotor and perhaps a mast-mounted sensor As far as the flight of the helicopter over the ground is concerned these may be added to form the total cross - 45 - section which total is used to calculate the signal to which the doppler filtering is to be applied In addition the rapidly spinning rotor produces a doppler high-frequency signal which is above the doppler frequency threshold and is not reduced by filtering even when the helicopter is hovering This high frequency signal is typically 8 dB below the main low-frequency rotor signal ' RJARS provides helicopter visibility modes via the parameter IHIDE which is 0 for fully exposed 1 for only the rotor showing and 2 if only the mast-mounted sight is showing or if the helicopter is fully concealed The equivalence of the latter configurations arises from the observation that if the helicopter is in a condition with only its sight showing it almost certainly is hovering The sight then looks like a small stationary sphere and should be indistinguishable from clutter to either a radar or an optical system Two formulations of detection probability are used in RJARS The first characterized by the scenario parameter PRBTYP 0 is identical to that in JARSM threshold The signal-to-noise ratio is compared to the receiver If it is less than -9 dB the detection probability PD is 0 If it is greater than 9 dB the detection probability is 1 For intermediate values PD is fitted with the form PD I sin S N dB -MDS dB 7 l8 2 18 The second or cookie-cutter detection probability type for which PRBTYP 1 tests whether noise or deception is being used for jamming If noise is used and the signal-to-noise ratio exceeds -6 dB then PD 1 If deception is used and the signal-to-noise ratio exceeds -3 dB then PD 1 Otherwise PD 0 This treatment permits calculation of clearly defined burnthrough ranges 'The author is indebted to RAND colleague Howland Bailey for this information - 46 - The variable PRBTYP is also used to select the table for evaluation of jamming effectiveness as determined by field data This will be discussed under tracking radars The detection probability is compared to a random number and the resulting detection choice established As discussed in the general description and also in Ref 1 detection is established if two of three consecutive scans yield successful results Once the target has been detected the fact of detection is held until the time TDROP which is the sum of the present time and the smaller of RSTMAX a library input chosen as a likely value for the maximum time a radar will retain memory of a target or the product of the radar scan period and the number of scans with successful detection When and if T exceeds TDROP corresponding to loss of detection the time and range are stored for the summary and the information printed 3b Measurement Errors If the detection is successful the next step is to calculate the measurement errors noise Sources of error included in UPDRS are glint and The theory of glint is given in Ref 4 Chapter 28 The time of integration of a search radar is usually long compared to the rate at which the returned signal fluctuates and the theory thereby may be considerably simplified The effective dimension of the aircraft ACGLN is taken as the larger of the projected wing and body dimensions which in turn are approximated by multiplying the square root of the broadside radar cross section by the sine or 65 times the cosine of the aspect angle This approximation comes from empirical fits to published data on aircraft dimensions The center of radiation of the signal fluctuates by about one quarter of the effective length and the corresponding azimuth and elevation fluctuations are AAZ 02166 GLN m R n mi 19a AEL AAZ4 19b - 47 - The error due to integrated signal-to-noise ratio is found from Ref 5 pages 46 and 51 as 20a AR C PW 4 S N NPLS ' AAZ 49 58vr- 20b HB S N NPLS lfl 20c AEL 49 58J4W VB S N NPLS ' where the limiting values for small and large S N for angular accuracy given in Ref 5 p 51 have been combined Here PW is the radar pulse width NPLS is the number of pulses integrated the same as N of Eq 14 and the other symbols are as before The values of Eqs 19 of normal distributions and 20 are the root mean square variances A subroutine NORMV produces two normally distributed independent uncorrelated variables per call It is used thrice to combine the errors from Eqs 19 and 20 to obtain the errors as sampled at each time step The resulting range azimuth and elevation errors are then combined to form the total position error 4 Output and Detection Table The signal signal noise nominal position and position errors are printed out under the control of the scenario parameters JREP PRNTMOD and IP JREP is the number of the Monte Carlo repetition currently being run and the detailed radar data are printed only during the first run PRNTMOD determines the output format If PRNTMOD S then a heading is printed followed by all the data per radar aircraft pair on a single line each value Otherwise the radar data have a descriptive word with As before IP sets the time step at which radar data are printed RJARS maintains a detection table similar to but more extensive than JARSM Each time an aircraft comes into the field of view of a radar the occasion is marked by incrementing the parameter ISF and the time and range are stored Each time during that pass that the radar establishes detection of the aircraft the parameter DTISD which has as - 48 - arguments radar aircraft and ISF is incremented and the time and range also stored These variable arrays are dinensioned so the aircraft may make srchno initialized to 10 separate appearances in the field of view and be detedted three times on each appearance So many appearances would correspond to rapidly fluctuating terrain and lowflying aircraft A normal scenario could expect to have mostly single detections per pass but jamming might cause loss and recovery of signal if the aircraft follows a complicated path Other quantities in the detection table are the flags DTFLG detection this pass DTNEW new detection this pass DTPSS established detection this pass and DTPSSL established detection last pass which last flag is used to establish loss of detection now and the hand-off variables DTRNG DTBRG and DTEL The values including errors are sent by the radar to its site UPDRS also has routines that apply to acquisition radars either dropping acquisition or turning the tracker on The conditions for activating these routines have been presented in the general description 5 Multipath and Clutter The multipath and clutter calculations in RJARS are closely based on those in ESAMS Ref 6 For search and track radars clutter reduces the effective signal-to-noise ratio and produces errors in the calculated position of the target doppler or CW seekers It also puts errors into pulse Multipath may increase or decrease the received signal strength and will produce elevation errors These effects will be described mostly on a qualitative basis For search or track radars clutter comes mostly from the region of the ground under the target The lateral extent of the clutter patch along the ground perpendicular to the line of site is approximately the product of the range and the antenna horizontal beamwidth The longitudinal extent along the ground parallel to the line of sight is approximately the product of the pulse width and the velocity of light The latter product is usually small compared to the rate of change of - 49 - the ground properties so the clutter region can be viewed as a thin strip on the ground perpendicular to the line of sight This description is limited to the condition where the longitudinal extent given above is small compared to the product of the range and the vertical beamwidth a condition usually satisfied except for very close targets The subroutine FACE examines the clutter patch and finds which terrain elements are included in it For them the terrain type is found and the reflection coefficient is calculated The data necessary to calculate the cross section per unit area as a function of frequency and angle of incidence are stored in the file MCLUT The subroutines CLUTTER POWER and RESPNS find the actual clutter power returned from each element For clutter power to actually reach the receiver the clutter patch must be visible The visibility may be modified by refraction or diffraction effects At present these are not modelled in RJARS The file RIDGE previously described contains the data for these visibility calculations The range to the patch is compared to the ridge data interpolated to the proper angle Since the number of ridges along the bounding lines of the target sector may be different for the two bounds the interpolation process is complicated If the ground is visible then its slope is examined to make sure that it is not in a selfshadowing configuration tilted away more steeply than the angle of incidence If the ground is visible the clutter power is calculated using the indicated subroutines The clutter cross-section per unit area of ground is determined at each relevant terrain element This cross section is a function of the frequency FRQ MHz the terrain type and the angle of incidence THETA The equation giving the cross-section SIGMA derived from ESAMS is SIGMA A FRQ 1 5E4 ' THETA C B exp -D l ROUGH FRQ 3E5 21 - 50 - The parameters A B C D and ROUGH the roughness in cm are stored in the file MCLUT as functions of the terrain type The cross-section per unit area for each element is multiplied by the pulse width and the velocity of light and the length of the element in the direction perpendicular to the line of sight It is then multiplied by the square of the antenna gain in the direction of the element corresponding to two-way propagation to yield the clutter power at the receiver elements The power is summed over the active terrain This power is filtered using the doppler filters described above actually the signal is reduced relative to clutter if the doppler frequency of the signal falls into the filter notch The filtered clutter power is added to the noise plus jamming to give the effective signal-to-noise ratio of the system and the mean azimuth and elevation of the clutter appropriately weighted are combined with the signal to give errors in the indicated position For low-flying aircraft it is quite possible that the clutter signal will be strong enough to mask the signal from the aircraft This is only likely for pulse not pulse doppler radars and because of the filtering aircraft flying in a direction perpendicular to the line of sight The effect will show in RJARS in the calculation of the detection probability for which the resultant signal may drop below the effective minimum detectible signal Sometimes if the aircraft is distant but visible the ground at the same location will not be visible permitting detection and then as the aircraft approaches the ground comes into visibility and the aircraft drops out of detection Multipath effects are also simulated in RJARS Multipath is a phenomenon involving reflections of the returned signal from the target against the ground If the angle of incidence of the ray from the target to the ground point and the ray from the radar to the ground point make equal angles with the local slope of the ground a condition known as specular reflection the ground signal may be very strong representation of multipath in RJARS is also derived from ESAMS The - 51 - Multipath signals come from a region on the ground surrounding the specular point or points If the terrain is flat this region known as the first Fresnel zone is a long narrow ellipse the size and shape of which are determined by the condition that the total path length of the rays from radar to ground and target to ground shall not exceed the total path length of the rays to the specular point by more than a half wavelength The program steps through the points on the ground below the sight line to the target For those points that are visible and not self-shadowed to either ray the angles of the rays with the local slope of the ground in the direction paralleling the sight line are found and tested for equality thereby determining the presence of specular points The size of the Fresnel zone is found from the elliptical formulas treating the return as coming from the tangent plane at the specular point approximation If the ground is rapidly varying this may be a bad However the complication of finding the actual shape of the region on the ground using the ray length criterion is so great that the simpler procedure has been retained The reflection coefficient at the specular point is found using the Fresnel reflection coefficients which are calculated from the dielectric properties of the ground The real and imaginary parts of the dielectric constant are stored as functions of terrain type in MCLUT They are actually functions of frequency but the variation over the microwave region is small enough and the values uncertain enough that constants have been used The reflection coefficient depends on the radar polarization stored in RDLIB and on the angle of incidence For most configurations of interest the angle of incidence is very small and the reflection coefficient is close to -1 The total multipath signal is found by multiplying the reflection coefficient by the area of the Fresnel zone and by the square of the antenna gain in the direction of the specular point Again if the zone is long the antenna gain should have been weighted over the zone is too complicated to consider This - 52 - The multipath signal is combined with the direct signal from the target using the proper phase determined by the difference between the lengths of the direct ray from the target and the reflected ray from the specular point As the aircraft travels this phase difference may change rapidly Fluctuations caused by multipath are well known in radar phenomenology The signals may add in phase causing an increase in detection range and then as the aircraft flies the return goes in and out of visibility as the interference of the rays changes from constructive to destructive This combined multipath signal is used to determine the target detectibility and the effective azimuth and elevation of the weighted combined signals provide azimuth and especially elevation errors The errors are not too important for search radars but may be a major effect for trackers 6 Optical Systems This completes the discussion of search radars We shall now describe the manner in which infrared and optical detectors are simulated in RJARS Infrared IR detection systems in RJARS are used only in the tracking state If they are in the connected control system they are assigned in the same manner as radars and go directly into the tracking state If they are autonomous they obtain their search information from optical systems Hence we shall defer discussion of the algorithms used for detection and tracking by the infrared systems to the section on tracking UPDRT and shall present the techniques used for optical detection As has been mentioned several times the ground defensive systems in RJARS are divided into controlled and autonomous classes All shoulder-fired IR SAMs and all freely moving guns not associated with radars are in the autonomous class The guns include main tank guns machine guns mounted on carriers and fixed weapons aimed by personnel They are designated as radar class 'G' persons with or without binoculars The optical equipments are By changing certain parameters the - 53 - optical devices could be considered to include low-level TV systems A random draw during the data input procedure determines which individual optical systems are using magnification The amount of magnification is a property of the equipment type stored in RDLIB and the random draw for each equipment is against 5 making it equally likely that magnification is or is not being employed 6a Detection Algorithm At the beginning of the simulation all optical equipments are on and in the W state Each will scan a scenario-assigned sector of responsibility beginning at the lower scan limit The scan rate is such that the fixation field of view is covered in the time it takes for a successful glimpse if the contrast is sufficiently high rates are about 5 to 10 degrees per second Typical scan If magnification is being employed the effective field of view is reduced so the scan rate is reduced proportionateiy The subroutine SECTSCAN moves the instantaneous direction of observation across the sector of responsibility and back at the scan rate The eye is treated as a contrast detector The algorithm for determining detection capability was developed by the Night Vision Electro-Optical Laboratory NVEOL 2 The calculations are performed by the subroutine OPDET The basic concept is that the probability of detection is a function of the number of resolvable elements on the target This in turn depends on the contrast of the target and the background and on a reference minimum detectible contrast The contrast between the target and the background is taken to be the difference in brightness between the two divided by the smaller of the two brightnesses Usually the contrast is taken as the difference in brightness divided by the background brightness The resulting expression is then attenuated by a function of the range With this definition the contrast can become infinitely large but can only become as small as -1 perfectly black 2 This algorithm has been provided to the author by RAND colleague Lloyd Mundie - target against any background 54 - Hence because of attenuation the definition strongly discriminates against the detection of dark targets against bright background which is the usual situation with low-flying aircraft in the daytime The algorithm may be traced to its source the Night Vision Laboratory who are usually interested in bright objects against dark background the converse situation We have chosen the unconventional definition given above which is symmetrical between positive and negative contrast At present RJARS contains no optically self-luminous objects except the flares used as IR countermeasures background are illuminated only by the sun All aircraft and As an automatic consequence of this assumption no optical systems can operate at night The flag INIGHT has been put into the scenario to provide for this condition The aircraft are treated as two-surface objects an upper surface directly illuminated by the sun and a lower surface illuminated by sunlight reflected from the ground directly below the aircraft The ground reflection coefficient is a function of terrain type and is stored in MCLUT The aircraft is split into three parts fuselage wings and tail The upper and lower surfaces have associated colors of paint the particular colors being scenario input parameters PAINTU and PAINTL for each aircraft RJARS recognizes eight colors each designated by a two character code as follows 1 Aluminum AL 2 Olive drab OD 3 White WH 4 Black BK 5 Blue BL 6 Gray GY 7 Green GR 0 Nonreflecting NR The value 0 is used for nonreflecting to designate the last color in the - set 55 - Other colors may be added and RJARS will allocate the appropriate space A reflection coefficient is associated with each color The instantaneous attitude of the aircraft is used to calculate which areas are parts of the upper surface and which areas are lower surface The tail is the same color as the upper surface The areas must be projected toward the line of sight The fuselage is approximated by a cylinder the wings and tail by planes fuselage is split into a nose area and a side area The The roll attitude of the aircraft determines which portion of the side area is upper surface The tail area contributes only to the upper surface The wings display their upper surface if the aircraft is rolled toward the line of sight their lower surface if it is rolled away contributes equally to upper and lower surfaces The nose area RJARS combines all the projected areas to obtain the full projected upper and lower surfaces The effective contrast of the aircraft depends on whether the sun is or is not in the field of view Observation toward the sun is more difficult than observation away from the sun The position of the sun is found from the time of day which is a scenario input Due attention is paid to the latitude hemisphere to ensure that the sun appears in the proper location is visible The flag ISUN in the scenario establishes if the sun If the angle between the line of sight and the sun is less than 180 degrees the sun is fully effective in reducing contrast The background of the target may be either sky or ground uses the ridge files to determine this RJARS Given the azimuth and elevation of the target RJARS tests the line of sight to determine if it lies above the highest furthest ridge in the given azimuthal direction Interpolation with respect to azimuth in the ridge file is necessary to perform this test If the line of sight lies above the highest ridge then the target is being viewed against a sky background If the line of sight is below the highest ridge then RJARS extrapolates the line of sight from the target range to the point where it intersects the ground The terrain at this location provides the background for the observation It is assumed that the variation of terrain type with location is sufficiently small that a single terrain - 56 - type can represent all of the terrain that is within the field of view The reflection coefficient of the ground at this location then gives the background brightness If we are dealing with a configuration without terrain VIS 0 then a smooth spherical earth is used the line of sight is checked against the effective horizon no refraction correction and if the background is on the surface an average terrain reflection coefficient 1 is used The contrast at the target is found by combining the quantities already calculated knowing the proportion of the target included in the upper and lower surface and weighting the reflection coefficient accordingly to obtain the effective contrast There are many details involving presence or absence of the sun in the field of view which puts factors of 5 in various elements of the expression The resulting contrast must then be multiplied by a contrast attenuation factor to find the contrast at the viewer This factor depends on the atmospheric extinction coefficient which is a function of the season the location and the seeing conditions It also depends on a parameter called the sky-ground ratio although it really has nothing to do with the physical sky-ground ratio within the field of view in optical history The terminology is embedded An examination of the data on these parameters showed that at least for European locations the values depended slightly on location so that dependence has been dropped The seasonal dependence split into two values designated summer and winter although summer conditions apply essentially in April through October and winter conditions the rest of the year The flag ISUMMER in the scenario 1 for summer puts the seasonal choice in the hands of the operator Similarly examination of data at European specifically German locations provided data for median seeing conditions and for conditions that are exceeded better for the observer only 10 percent of the time ' The flag ISEEING in the scenario gives this choice to the operator 3 The values of the parameters are in the file IRLIB These data examinations were performed by RAND colleague Horace Ory - 57 - With the choices established the contrast at the target is attenuated with range to give the contrast at the viewer The attenuation equation is 22 VIEWER CONTRAST TARGET CONTRAST 1 SKG exp EXT RNG - 1 The parameters SKG sky-ground ratio and EXT extinction coefficient are two by two matrices with arguments ISUMMER and ISEEING The numerical values are stored in IRLIB The number of cycles separable visual elements across the target is proportional to the magnification proportional to the angle subtended by the smallest dimension of the target at the viewer and is a function of the contrast at the viewer Analysis' has shown that the dependence on viewer contrast is closely approximated by a linear function cF the logarithm of the contrast so the number of cycles C is given by C MAGNIFY 1 22 log abs VIEWER CONTRAST 4 09 23 FUSELAGE DIAMETER 6 08 RANGE Here MAGN FY is the magnification of the binoculars the fuselage diameter 'feet has been assumed to be the smallest dimension of the aircraft and the factor 6 08 adjusts dimensions If the number of cycles is negative corresponding to a small region lying between plus or minus 00044 around zero contrast the number is set to 0001 The problem it with the curve fit and under such conditions the probability of detection should be negligible The detection probability is a function of the number of cycles divided by a minimum number of cycles required for detection 'Private communication from RAND colleague Howland Bailey It may be - 58 - split into the product of a static part and a dynamic part where the static part is the detection probability given infinite observation time and the dynamic part represents the effect of the finite observation time With C the number of cycles given by the equation above and M the minimum number then Howland Bailey's analysis shows that the static part may be closely represented by S - C M 2 7 0 7 C M c M 2 7 0 7 C M 24 When the number of cycles is small compared to the minimum number this is approximately C M 2 50% at C 1 7 and tends rapidly to zero 1 94 5% at C M 2 and 99 5% The probability is at C M 3 It has been found by extensive field testing that to detect an aircraft-type target that is to determine that it is present the minimum number of cycles M should be set to 2 To recognize it that is to be able to observe enough features to determine what type of aircraft is present requires M 3 5 These values are used in RJARS for these two functions The dynamic part may be represented in the form 25 PD I-exp - C M ITIME I 45 ANGVEL 6 8 Here TIME is the time that the observer dwells on the target scanning it is the glimpse time about 1 3 second it is the time he continues to observe If he is If he is staring The variable ANGVEL is the angular velocity of the target in degrees per second This expression comes from field tests in which the improvement in detection capability of the eye when observing a moving target was evaluated The factor 6 8 in the exponent is an experimentally determined quantity found by the original researchers from curve fits to the data - 59 6b Control of Optical Systems With this algorithm in hand we shall now describe how RJARS handles optically aimed weapons sector using M 2 F-ch initially scans its search If an aircraft is in the sector not over the horizon and within the maximum range capability of the observer which is taken to be that range at which the magnified target minimum dimension subtends an angle of one minute of arc then the subroutines SECTSCAN and INBEAM are used to ascertain if the observer has scanned over the target during the current time step If he has the algorithm OPDET is used to determine whether detection actually takes place It has been found by testing the algorithm that for the low-reflectance paints used on most aircraft the detection range is quite short If the target is detected the viewer goes into an acquisition phase He or she ceases scanning and be74-s to stare at the nominal target direction step The observation time in the algorithm is now the time At each time step the detection probability is calculated with M 3 5 corresponding to recognition If the recognition test is successful then the system goes into the track phase If the viewer is controlling an IR SAM the IR detection system is activated and it attempts to lock the IR seeker on the target fire control system begins its calculations the description under UPDRT The gun is aimed and the For further details see While the system is in acquisition it can move to outside the sector of responsibility If the recognition test is unsuccessful the detection probability is calculated with M 2 to establish if the target is still being observed If the detection test is successful the observer continues to stare and tests again at the next time step If the test is unsuccessful the system reverts to scanning starting at the currently perceived direction of the target - 6c 60 - Cueing by Communications Alerting This presentation describes the operation of the optical weapons when their operators have no information about the battle configuration RJARS provides them with broadcast information as well If a search radar located somewhere in the field of action detects an aircraft and reports this to its command site then the command site not only assigns a tracker from among its own resources but begins broadcasting the detection to all the sites in the field described This has already been When an observer receives the broadcast information about the location of a potential target the range and azimuth are calculated If the azimuth is within the sector of responsibility and the range is within the horizon and maximum detectibility limits then the scan pattern is changed to a sawtooth centered around the target azimuth with a width determined by the library input parameter SECTWIDTH which is stored in RDLIB in the po3ition occupied by RDLVUL 1 for radars optical systems are immune to antiradiation missiles so their variables can be used for other purposes This restricted scan width has usually been set to plus or minus degrees narrower than the usual scan limits but wide enough that if the aircraft turns while approaching it can still usually be found If the system is in the acquisition phase and loses detection but has been cued to the target it will revert to search over the cued sector If the aircraft leaves the sector of responsibility while the system is in cued search the system will revert to uncued search over its original sector starting at its present position If it goes into track the observer returns to uncued search over the original sector If the present position is within the sector he or she begins at the plesent position If it is outside the viewer slews to the nearer sector limit and begins scanning inward This completes the discussion of searching radars and optical systems - 61 E UPDSI--SITES AND ASSIGNMENT Most of the material on sites and assignment is already presented in the general description where the tests involved in assignment are listed A number of flags are used to set the assignment conditions The tracker assemblage is first tested to ascertain if all trackers in the system are busy by comparing the variables RTNSI the number of trackers at each site and RTNSIA the number of trackers at each site that have been activated If no trackers are available anywhere RJARS announces the condition and exits from UPDSI Otherwise it selects the best data on each aircraft and performs the assignment process as described Among the flags are ASFIRDET Some radar has detected the aircraft ASINFLD Aircraft in the field of action SIPSFLG CSPSMFLG Data on the aircraft exist at a specified site or command site RSDEAD RTDEAD Search acquisition or track radar dead must be false ASRTKFLG ASRTMFLG Aircraft already in track at site or command site ASRAKFLG ASRAMFLG Aircraft already in acquisition at site or command site SMSTATE State of the SAM set associated with the tracker must be A - available ASHOMFLG Aircraft on way home INOUTFLG Whether inbound or outbound aircraft are being tested These two flags are used in conjunction to determine priority RTFLG Tracker already assigned RSAFLG Acquisition radar associated with tracker already assigned - 62 - When all these flags have their proper values the numerous tests listed in the general description will be satisfied and a tracker will be assigned to the aircraft During the simulation the communications links between sites and command sites may be cut or connected The condition is marked by the flag SICOMFLG 1 connected 0 isolated If the command CUT is given to the fictitious NAC l aircraft in flight maneuvers parameter X site in question K see the description of flight maneuver parameters in UPDAC then operating acquisition or tracking radars ASRAMFLG or ASRTMFLG 1 signifying they have been turned on by command site M are switched to site-autonomous operation ASRAKFLG or ASRTKFLG 1 and the site K is not included when the command site M to which site K had formerly reported tries to assign a tracker to a new aircraft The command CON reverses the process reconnected only to its original command site A site can be Since there is no interaction between command sites the situation corresponds to independent battlefield commands As described previously if a command site gets information on an aircraft it broadcasts it to the field What actually happens in the simulation is that a flag CSCOMALERT is set for that command site and that aircraft The flag is set only if there are data at the command site about that aircraft CSPSMFLG 1 and the flag CSCOMALERT is not set Thus the flag will not be continuously reset newly set the sites will be alerted to that aircraft If the flag is For those command sites that have no reporting search radars the alerting of the site causes it to assign one of its trackers using the standard algorithm for isolated sites The optically aimed weapons belonging to any alerted site will be cued to the aircraft At the moment the battlefield dimensions treated by RJARS are usually such that the information transmission via radio link is certain although a message probability is included in the calculations may be included in RJARS in the future A radio propagation model The announcement of broadcasting the command alert is printed each time it occurs When there is no information on the aircraft at the command site CSPSMFLG 0 and the command alert is on it will be turned off - 63 - As long as at least one command site is broadcasting the alert on a given aircraft the sites will remain alerted When finally none of them is broadcasting or if the aircraft is shot down the site alert will be turned off and the equipments at each site will revert to the W state for radars and uncued search for optical systems F UPDRT--TRACKING RADARS When the acquisition radar associated with the tracker has marked acquisition by achieving three successes in no more than five scans it turns itself off and turns the tracker on in a time RTSCN Unlike RSSCN tne scan period of a search radar which measures duration of rotation RTSCN corresponds to the lock-on and settling time of the tracker circuits The tracker will then follow its target using range and angle servos and have both steady and random errors It will provide position information at interpolated time steps to its associated SAM guidance system 1 Signal and Jamming Calculations First the jamming power is calculated Since each tracker may be susceptible to range deception angle deception or both the jamming powers in the range and angle channels are calculated separately using the appropriate jamming effectiveness factor The signal and signal- to-noise ratio in both channels are then determined RJARS has the ability to use externally generated jamming effectiveness tables to determine the susceptibility to jamming have been collected for two types of tables Data The first uses measured results from flight tests and averages over all kinds of variables to find a net rcduction in kill probability when a particular jammer is used against a particular radar These data are used by setting the scenario parameter PRBTYP equal to 2 Under these circumstances the tracker and SAM guidance system will be treated as if they were unjammed out to the point of calculation of the kill probability in the SAM endgame The kill probability is then reduced by the factor in the - 64 - table The second table is based on measured data that give the jamming effectiveness as a function of signal-to-noise ratio The actual data were limited in that almost all of them referred to a single value of S N which we treat as a threshold such that the indicated effectiveness is achieved for S N values above that threshold There were effectiveness values for two values of S N for a particular jammer-radar combination indicating an approximately linear falloff of effectiveness below the threshold and we arbitrarily extended that result to all jammer-radar pairs for which data were collected The second type of effectiveness table is used by setting PRBTYP equal to 3 RJARS then again treats the system as unjammed out to the endgame then calculates the signal-to-noise ratio determines the effectiveness and reduces the kill probability as above RJARS can use either fixed or automatically adaptive servo If the fixed bandwidth is selected the bandwidth in both bandwidths the range and angle channels is set to 1 5 Hz a hard-wired number that appears to be representative of many radars If automatically adapting servos are used characterized by setting the input parameter SRBMOD A then the following theory is applied 2 Tracking Errors The theory of error in tracking radar servos leads to the expression for the RMS error in the azimuth angle channels due to inability to follow accelerated motion Ref 5 p 307 ERR 4 I ACC I SRB 2 26 Where ACC is the acceleration in angle SRB the servo bandwidth and ERR the error This error is a steady lag if the motion is a constant acceleration or is an RMS fluctuation if the acceleration is fluctuating The error pro- iced by noise jamming is Ref 5 p 278 - 65 - ERR 637 NHB SRB PRF S N ' 27 where NHB is the horizontal beamwidth of the radar antenna and PRF is the pulse repetition frequency The combination of these two sources of error may be minimized by choosing the servo bandwidth so the derivative with respect to the servo bandwidth of the sunj of the errors is zero This optimum servo bandwidth is SRBp t 6 3 PRF S N '2 I ACC I NHB O 4 28 If the bandwidth is less than 0 5 Hz the system will be unable to follow reasonable motions of the aircraft so the bandwidth should be cut off on the low end by 0 5 Hz The high end of the servo bandwidth should be below the lowest vibration frequency of the antenna assembly This vibration frequency is inversely proportional to the dimensions of the antenna which in turn are inversely proportional to the frequency and the antenna beamwidth An estimate of the proportionality constant yields for the maximum servo bandwidth in the azimuthal channel RTMHSB 0013 FRQ NHB Similar calcolations apply to the elevation channel with NHB replaced by NVB A tracker normally operates by measuring the error signals ir the several channels and applying corrections co drive these signals toward zero If the errors are too large the slope detector that provides the tracking signal will be forced out of its capability range and the tracking lock will be broken Angle tracking circuits usually can operate in the presence of a much poorer signal-to-noise ratio than can 29 66 range tracking circuits - The theory Ref 5 pp 281 and 369 indicaLes that the integrated signal-to-noise ratio must exceed about 8 dB for the range circuit to maintain lock but the angle circuit only requires -6 dB Thus the tracker can be in any of four states--range and angle range only angle only or neither depending on the jamming susceptibility RJARS treats the four conditions separately Thk ime spent in each state after the tracker is turned on is designated by RTTIMRA range and angle RTTIMRNA range no angle RTTIMNRA no range angle and RTTIMNRNA no range no angle A counter RTJMCNT determines for how many time steps any function has been jammed This counter is used to cause an already launched SAM that is still approaching its target to lose guidance if the radar has been jammed too long A flag RTJAMFLG prevents launch of a SAM while the tracker lock in range or angle is broken The time step is generally long compared to the tracking servo response time so the errors at successive steps can be treated as uncorrelated The subroutine SRVERR combines glint and noise errors as independent normally distributed variables and adds the acceleration leg term as a bias error If both range and angle locks are broken the condition is printed out If only range tracking is effective the error in range is calculated using SRVERR without a glint term and the signal signalto-noise range and range error are printed If only angle tracking is operating the errors in azimuth and elevation are calculated as independent quantities and the signal signal-to-noise angles and angular errors are printed If all channels are working all errors are calculated and the signal signal-to-noise range angles range error angle errors and total position error are printed errors are in feet angle errors in degrees Range and position - 3 67 - Conditions for Dropping Track Tracking will be maintained until one of the several conditions for dropping track is satisfied at which time a subroutine DROPTCK will turn the tracker off return the tracker SAM system to the available state unless the tracker has been killed by an ARM or the SAM launcher is out of missiles and record the results of the tracker-aircraft interaction 1 The conditions for dropping track are Target shot down either by a SAM from the launcher associated with the tracker or by a SAM from some other command site A command site will assign only one tracker to an aircraft an isolated site no communication likewise 2 Tracker killed by an ARM The ARM success probability is calculated in the section UPDAR which follows UPDRT in the subroutine sequence so the tracker must be turned off at the next time step 3 Tracker reassigned If the tracker is following a home-bound target and it receives a command to track an inbound target the tracker must go off so the acquisition radar can come on 4 Launcher reloading or exhausted If the launcher shoots at a target and misses the tracker will remain on the target for another shot unless the launcher has no missiles remaining That can be a temporary condition missiles available at the site to reload the launcher or permanent all missiles exhausted 5 Target goes over horizon This situation will have a delay of three tracker settling times so track may be maintained during short terrain masking intervals 6 Tareet goes beyond maximum range of tracker This will occur rarely except for very low radar cross-section targets since the maximum range of the radar is usually much greater than the maximum range of the SAM - 68 - 7 Target not coming within critical radius The tracker was assigned under the condition that the target was coming within the maximum range of the SAM If as a result of an aircraft maneuver this is no longer true there is no point in maintaining track 8 Target outbound beyond the critical radius of the SAM with SAM not launched This permits the tracker to hold the track as long as possible 9 Target outbound while the tracker is jammed for three time steps with the SAM not launched Because of the different range dependence of signals and jamming if a target is outbound and achieving effective jamming the signal-to-noise ratio will become worse as the flight continues so the tracker will not recover and might as well quit Effective jamming means that range or angle lock is broken 10 Target outbound while the tracker is in excess clutter for three time steps with the SAM not launched If the clutter is bad the tracker probably cannot recover the track 11 Tracker jammed too long with the SAM in flight is jammed the SAM will fly unguided If the tracker We allow three full time steps to elapse before tracking ceases since the system might recover then give up Again being in excess clutter for three time steps will cause the tracker to break lock 4 Interpolations and Correlated Errors If a SAM is in flight it requires information more frequently than once per time step INTERPOL This information is supplied by a subroutine A scenario parameter DTG gives the time requirement for the SAM and the time interval DT is divided into NGUI segments each of length DTG DT which should be chosen to be an integer We have sually set DTG 05 which with DT 2 5 yields NGUI 50 segments Values of the range azimuth and elevation from the tracker to the target are maintained for the present and two previous time values they were used earlier in UPDRT to calculate the target and angle - accelerations 69 - A quadratic interpolation formula is used to obtain the range azimuth and elevation at the interpolatory time values from which the true or ground reference aircraft position ACLATG ACLONGC ACALTG is calculated Errors must now be added For this short time interval the errors in each channel are not independent but are correlated in time so the subroutine SRVERRCOR is used for calculation SRVERRCOR connects the past and present values of a normally distributed variable by the relation 30 ERR PAST COR PRES sqrt 1 - COR COR VAR2 where PAST and PRES are the previous and current values of the variable COR the correlation between them a function of the time spacing DTG and VAR2 is one of the normally distributed zero mean unit standard deviation variables provided by NORMV For both glint and noise errors the correlation is an exponential function of time For glint Ref 5 p 288 the exponent is proportional to the change in apparent angular position which in turn is proportional to the angular rate frequency and target dimension yielding in azimuth 31 COR exp - 041917 I dPHI dt I FRQ GLN DTG where dPHI dt is the angular rate in the azimuth channel GLN the effective length of the target and the other symbols as before The coefficient is a complicated combination of constants and unit conversions For noise the exponent is the change permissible during one servo bandwidth so COR exp -2 PI SRB DTG 32 70 - Interpol uses SRVERRCOR to calculate the correlated errors in each channel The glint noise and acceleration components are combined as independent variables to give the total error in each channel These are added to the range azimuth and elevation as previously interpolated and then these error-affected values are used to calculate the interpolated and corrupted aircraft coordinates ACLATI ACLONGI ACALTI Their values are where the tracker thinks the aircraft is located and they are the values furnished to the SAM guidance system 5 Towed Decoys As previously mentioned the aircraft may be towing decoys used to jam trackers There are five techniques available to a decoy Since jamming techniques 0 noise 1 search deception 2 range deception 3 angle deception and 4 range and angle deception are already assigned these techniques are designated 5 Towed reflector The decoy itself small and cheap may be carrying one or several corner reflectors that make it look like a large target The tracker may then follow the decoy instead of the aircraft 6 Towed noise jammer The decoy directed by a warning receiver which may be on the aircraft or on the decoy itself may radiate noise This would be most useful against home-on- jam counter-countermeasures 7 Towed repeater The decoy amplifies and repeats all tracker signals it receives in its coverage band providing the tracker with a strong false target For those trackers that follow the center of radiation of the received signal the information transmitted to a command guided missile will be erroneous 8 Blinking noise noise The aircraft and the decoy alternately radiate The idea is to make the tracker oscillate between the two targets with a resultant loss in accuracy - 9 Blinking repeaters 71 - Like technique 8 but the reradiated signal is an amplified repeated signal It is expected to be more effective than 8 The blinking techniques can be employed by two independent aircraft The commands BLINK and BLKPR in the aircraft command list see UPDAC make the aircraft partners and allow them to use these techniques 5 6 Semiactive Systems and Illuminators The SAMs associated with tracking radars are of two types command guided and semiactive The command guided SAMs use information directly provided by the tracker for their guidance systems Semiactive SAM systems have an illuminator associated with the tracker The illuminator is slaved to the tracker and radiates a signal usually either CW or pulse doppler which is reflected from the target and received by the SAM in flight The seeker on the SAM is a monopulse receiver which uses servos and points itself at the center of radiation of the reflected signal The details will be presented in UPDSM Such receivers are-susceptible to the decoy techniques described above The illuminator is turned on at the time of launch If the target is distant or of low radar cross-section and the illuminator is weak which is a quite common situation the received signal at the seeker may be below the threshold value which the seeker requires to operate What RJARS does is to provide the semiactive seeker information at launch on the aircraft current position and velocity vector is adequate the seeker behaves normally If the seeker signal If the signal is below threshold the seeker calculates the projected position of the target 5 1t is the author's opinion that the blinking techniques are less effective against seekers than the decoy-only radiating techniques With blinking the seeker will swing from one target to the other When the SAM is sufficiently close one of the targets will go out of the field of view and the seeker will lock on the other If the final target is the decoy great but if it is the aircraft curtains Since there is no relation between the time phase of the blinking cycle and the distance of final lock on the chances are 50 percent that the blink cycle will be in the wrong phase Hence the author believes that the blinking techniques 8 and 9 should not be used against illuminators - 72 - assuming no maneuvers and guides toward that point If eventually the signal becomes strong enough the normal guidance system takes over The main advantage of a semiactive system is that the tracker need only point toward the target with sufficient accuracy to keep the target within the illuminator beam Semiactive systems are very well suited for track-while-scan operation in which one tracker aims several illuminators the future This has not been implemented in RJARS but it may be in Also the accuracy of the missile does not degrade as badly with range as it does for command guided systems The angular accuracy of a tracker will fall as the square of the range proportional to the square root of the received signal power two-way propagation while the accuracy of a seeker will be almost independent of range short distance from seeker to target during final approach providing strong signal Consequently many modern systems use the semiactive approach Clutter and multipath effects are included for trackers calculations are identical to those for search radars However the effects of clutter and multipath are more severe for trackers be broken by clutter or the errors may become large The Lock may If the multipath effect is strong and the phase relations are right the tracker will point at the ground below the target the centroid of the target and its image RJARS follows ESAMS in making detailed calculations of the location of the specular point and the amplitude and phase of the reflected signal A separate random number generator NORMC is used so the random number sequence for the main simulation will be the same in the presence or absence of clutter and multipath The multipath effect on the signal amplitude and the elevation error are worked out in detail Trackers have procedures to reduce the effects of clutter Following ESAMS these techniques are subsumed in a single expression TRKSCVD tracker subclutter visibility in dB an input number stored for each tracker type in RDLIB After the clutter signal not the multipath has been calculated it is reduced by the appropriate factor Generally pulse doppler radars have better clutter reduction than ordinary pulse radars - 7 73 - Infrared Systems We shall next describe the methods used by IR systems in RJARS The assignment of IR trackers either centrally controlled or autonomous has already been discussed so it will be assumed that the IR equipment is in the tracking state RDSTATE 'Q' used to determine signal strength will be presented The algorithms All the numerical data used for IR systems and also for optical systems are in the file IRLIB Most of the IR material has been derived from ESAMS An IR tracker detects the thermal radiation from a target finds the direction of the center of radiation and uses the resulting angular information to guide its missile The tracker is located on the missile and we shall consistently refer to it as a seeker To develop the theory of IR seekers we need to know the properties of the radiation from the source 7a Source Radiation and Attenuation Following ESAMS we assume that the seeker works in either of two spectral bands and measures the radiation from the source integrated over the appropriate band The radiation from each type of aircraft is presented in tables similar to the radar cross-section tables For each band the radiant output from the aircraft in watts per unit solid angle watts ster is given as a function of the azimuth and elevation angles of the line of sight to the aircraft Azimuth is measured in the horizontal plane of the aircraft with zero at the tail 180 degrees at the nose and right-left symmetry assumed Elevation is measured from directly below 0 through the horizontal plane 90 to directly above 180 The tables are in steps of 15 degrees This procedure regards the aircraft as a single source of radiation with a directivity determined by the shadowing of the hot parts around the engines by the body structure The parts of different temperature radiate different amounts of energy in the two wavelength bands so the directionality is different We shall shortly say more about the separation of the radiation into body and jet plume radiation - 74 - The radiation at the source will be attenuated as it travels through the atmosphere The attenuation is a function of wavelength so the proper procedure is to take the radiant source energy in each direction as a function of wavelength multiply by the attenuation factor at that wavelength the exponential of the product of the attenuation constant and the range then integrate over the wavelength coverage at the seeker an off-line calculation This is sufficiently complex that it requires The results for ESAMS were developed using an unspecified computer program Some further calculations at RAND used the LOWTRAN program For proper representation of the attenuation it should be presented for each aircraft type as a function of type wavelength range azimuth and elevation ESAMS has simplified this situation by using the same attenuation for all aircraft types Thus the attenuation data in IRLIB are presented as ten tables For the two bands and for five ranges 1000 5000 13000 30000 and 99000 feet the tables give the attenuation for elevation angles between 0 and 180 degrees and for azimuth angles between 0 and 90 degrees tail to beam It is assumed that the engine radiation is sufficiently shielded in the forward hemisphere that only the body is radiating so the attenuation in the forward hemisphere is taken as the same as in the beam plane The effect of this approximation is that all aircraft are treated as having the same wavelength-dependent shielding in the sense that the spectral distribution of the radiation in a given direction is taken to be the same for all aircraft assumption This is clearly a questionable For example an aircraft with engines above the wing such as the A10 will put less engine radiation into the lower hemisphere than will an aircraft with engines below the wing Since the engine radiation is hotter than the body radiation more of it will lie in the shorter wavelength band Since the spectral distribution in the bands is different for the two types of aircraft the attenuation will be different and this should show in the tables However lack of data on the variation of spectral distribution with type has caused us to retain the ESAMS procedure - 75 - RAND colleagues Lloyd Mundie and Horace Ory studied this effect For two fixed-wing aircraft types AlO F16 and three helicopters AH64 0H58 V22 the radiation and its spectral distribution were calculated as a function of observation direction The LOWTRAN program was used to obtain the attenuation for each type as described above The original radiation was split into the body including engines and the jet plume and separate calculations were performed for each These improved data and any that may result from further calculations will be incorporated into RJARS in the future with a flag to show for any aircraft type whether it uses the original calculations or the new and improved variety 7b Signal Calculations The detailed calculations performed by the subroutine IRSIG determine the angles between the line of sight and the oriented aircraft Interpolation in the radiation tables gives the radiant output of the aircraft in the proper band in the indicated direction The range is determined this information is not known to the actual seeker but it exists in reality the program knows it and can use it to perform the calculations and three-variable interpolation in the attenuation tables gives the attenuation factor The product of the radiant intensity and the attenuation divided by the square of the range gives the signal received at the seeker When the Mundie-Ory model is incorporated the signal from the body and the plume will be found separately and added In the daytime the only relevant time for IR operation the aircraft will be illuminated by the sun and the seeker will receive the reflected sunlight The reflected solar energy is treated as a fixed constant for each band multiplied by the attenuation factor of solar radiation in that band Many seekers use detectors that work in an IR wavelength band where solar radiation is negligible The solar signal is added to the self-produced signal to give the total signal to the seeker - 76 - The signal is divided by the equivalent noise of the seeker to obtain the signal-to-noise ratio The equivalent noise of an IR system is subject to several mutually inconsistent definitions The one used in ESAMS and RJARS is that the equivalent noise is the sensitivity of the detector in watts sqm a property of the material multiplied by the detector area divided by the area of the collecting mirror and divided by the transmissivity of the seeker optics It thus is the sensitivity of the detector divided by the optical gain of the system and is the minimum detectible signal at the input to the optics The signal calculated above in watts sqm is at the input to the optics so the calculation is consistent For the system to operate properly the signal-to-noise ratio must exceed a threshold value 2 ESAMS and RJARS generally set this value to At this point an approximation to the effects of background clutter is introduced If the field of view of the seeker when pointing at the target includes the ground the threshold is increased from 2 to 7 A correspondence with BDM Corporation the developers of ESAMS revealed that this approximation was provided many years ago by the Army Helicopter Group in St Louis Discussions with RAND's specialists in IR systems indicate that not enough is known about the effects of IR ground clutter to warrant further investigation When the IR seeker is initially turned on it begins to calculate the received signal When the signal-to-noise ratio exceeds the clutter-modified threshold the integer SKLOCK is set to 2 and the launch procedures proceed exactly as for radar equipments If the signal-to-noise ratio drops below threshold SKLOCK is decremented If SKLOCK drops to 0 meaning loss of signal for two time steps the seeker will drop track If the SAM has not been launched the seeker will continue looking for the target If it has been launched self- destruction ensues IR seekers can be decoyed by flares RJARS treats this possibility launching and flying the flares and finding the resultant combined signal and angular displacements The details are in UPDSM - 77 G - UPDAR--ANTI-RADIATION MISSILES As mentioned in the general description each aircraft may carry several anti-radiation missiles Each missile has an associated frequency band corresponding to its receiver coverage ARMs may have scenario-specified targets corresponding to known radar locations or may shoot at targets of opportunity flight and results for the ARMS UPDAR controls the assignment There is no interaction between ARMs and IR or optical systems UPDAR first checks for each aircraft that it is in the field of action has missiles on board and either the aircraft is still alive or ARMs it has launched are still flying It then checks the radars to verify if they are turned on and if they have been registered by the warning receiver on the aircraft A flag ARMLNCH ascertains whether an ARM has already been launched from that aircraft at that radar Only those acquisition or tracking radars that are pointed at the aircraft are appropriate for ARM attack If no ARM has been launched at a radar UPDAR determines whether one should be launched It tests that the aircraft is approaching the radar and then checks for each missile still on board that the radar range is between the ARM's maximum and minimum flight ranges that the radar frequency is within the frequency band of the ARM and that the ARM is either preprogrammed for that radar or is opportunistic If all these Londitions are satisfied an ARM is launched The counter ARMNL tells the aircraft how many ARMs it has left ARMNL 0 no further ARMs may be launched by that aircraft If Since the ARMs have self-contained guidance they can continue flight even if the parent aircraft is shot down at least until the target radar ceases transmitting The ARM trajectory used in RJARS ig much simplified from what we believe to be actual ARM trajectories The ARM flies at constant velocity rather than initially accelerating away from the aircraft and then slowing from drag The ARM velocity used in RJARS is the velocity with respect to the ground and may be thought of as the sum of the velocity of the launching aircraft assumed to be aimed at the target - 78 - radar and the velocity imparted to the ARM by its propulsion system Aircraft aiming maneuvers are not included in RJARS The ARM is launched on an initially lofted trajectory on the bearing connecting the aircraft and the target It goes into a l-g pitch-down maneuver until the pitch of the vector velocity of the ARM drops below the line of sight from the ARM to the target radar The pitch is then maintained along the line of sight so the trajectory is straight The position of the ARM and its range to its target are printed out at each time step during flight Anti-radiation missiles require a radar signal for their guidance system operation If the target radar goes off the air which may occur for the variety of reasons presented in the sections on radars then an ARM used in RJARS will lose guidance It will continue to fly for a time ARMTDLY a library input with the kill probability reducing linearly to zero at the end of the no-guidance interval The alternative possibility that the ARM can divert to another target has not been implemented except as described in the next paragraph This is a limitation of the simulation In normal operation if an acquisition radar locks on to its target it turns its tracker on and turns itself off that an It is possible 'M was in flight against that acquisition radar especially if the radar is being jammed If the acquisition radar and its tracker are in close proximity the hard-wired value is 01 nmi 60 ft and both the acquisition radar and the tracker are in the frequency coverage of the ARM then the ARM will transfer its attention to the tracker Conversely if the ARM was directed against a tracker which is in autonomous operation and reverts from track to acquisition or search the ARM will continue to fly against that tracker if the acquisition or search frequency is in the coverage band of the ARM The arrival of an ARM at its target is marked by the ARM altitude dropping below the radar altitude The time of arrival is then determined by interpolating the linpar trajectory back to the radar altitude The vulnerability of a radar type to an ARM type is a parameter array RDVUL five elements per radar corresponding to five - 79 ARM types which was stored during the data read-in process This vulnerability is compared to a random draw and the outcome of the ARM's attack on the radar thereby determined and printed If the attack is successful the flag RSDEAD search radars or RTDEAD track radars is set equal to 1 and that radar will no longer participate in the simulation H UPDSM--SURFACE-TO-AIR MISSILES Much of the theory and programming for surface-to-air missiles has been derived from the computer program ESAMS Ref 6 After the tracker has established lock-on to the target aircraft its associated SAM system must be alerted counted down the SAM launched flown under its propulsion system guided to the target and a mission outcome determined These procedures are implemented in UPDSM An option parameter NOSHT will bypass UPDSM if it is set equal to Y This option may be used if it is desired to study only the target-radarjamming interactions 1 Sequence of Operations The condition of a SAM is characterized by the parameter SMSTATE which has the following possible values A Available P Preparing F Ready refire R Reloading E Exhausted B Boosting I Interstage S Sustaining C Coasting - 80 - The SAM may be an anti-aircraft artillery weapon The identification is determined by the parameter SMGUICL which has the values A Artillery C Command guided S Semiactive I Infrared An unassigned SAM is in the A state If it is determined that it should be launched it goes into the P state for countdown If it is launched successfully it steps through B I S and C in the flight After the attack endgame the number of missiles at the launcher is checked If they are all gone but there are still missiles in storage at the launch site the system reloads in state R If all missiles at the launch site have been expended the launcher falls into state E and leaves the simulation If there still are missiles at the launcher then if the attack was successful the system reverts to state A for further assignment If the attack was unsuccessful the system enters state F where it remains assigned to the current target but the reaction time is reduced from that of state A The reaction and refire times in RJARS are drawn from distributions Either uniform or normal distributions may be employed the control being the character flag RCTDISTRIB in the scenario which may be set to U or N For each SAM type two numbers are stored for reaction time and for refire time representing the upper and lower limits for each A uniform distribution draws between these limits a normal distribution uses the average of the two for its mean and 1 6 of the difference for the standard deviation with the distribution cut at the limits 3 a points It is expected that lognormal distributions for reaction and refire times will be added to RJARS in the future Only SAMs in state A or state F may be launched If the tracker has been tracking its target in both range and angle for more than two time steps then the call goes to the SAM system to execute the subroutine LNCHCALC In this subroutine the flight of the SAM is approximated as a constant velocity flight after booster cutoff The - 81 - aircraft path is projected with its present velocity in its present direction The SAM path is drawn to intersect the aircraft path and the pitch and heading of the SAM are adjusted so that when the paths cross both the SAM and the aircraft are at the point of intersection The time until intersection includes the countdown delay time during which the SAM is stationary but the aircraft is flying When the range from the SAM to the radar is equated to the range from the aircraft to the radar there results a quadratic equation in the time This equation is solved by LNCHCALC to obtain both time and range of intersection If the resulting range lies between the maximum and minimum range capability of the SAM library inputs then the SAM enters state P and a nominal launch time is set at the countdown duration from the present upward adjusted to an exact time step If the SAM is an anti-aircraft artillery weapon a different procedure must be followed The approximation of constant velocity is not appropriate for a shell which starts at high velocity and slows down from the effects of drag and gravity The shell trajectory is approximated as a constant drag coefficient flight so the velocity is an inverse function of time and the range is a logarithmic function of time This trajectory is employed to find the point and time of intersection the launch elevation and the launch heading These values are then corrected to first order for the effects of variable density and gravity drop When the nominal launch time is reached the current situation is checked The aircraft may have maneuvered so that if its position projected to the time of SAM booster cutoff is either closer than the range of booster cutoff or beyond the maximum range capability of the SAM Also it is possible that the tracker is now being jammed If these events oe-'lr the SAM launch is delayed till the next time step If not the launch command is given The SAM launch reliability is compared to a random draw If there is a failure the system transits to the F state and begins another countdown Otherwise the SAM launch parameters are initialized The time and range of the expected intercept point are found from LNCHCALC - 82 - Projecting the aircraft forward by this time yields the coordinates of the projected intercept point from which the SAM launch azimuth and elevation are found The SAM elevation is incremented by a loft angle The aircraft may be in a dive at present which would cause the projected intercept to be underground set to thp loft angle If so the launch elevation is The SAM enters the B state a launch flag SMLNCHD is set and the success or failure is printed If the launcher is an optically aimed gun the accuracy of aiming is simulated by the parameter SKAIMERR stored in RDLIB Independent normally distributed errors with mean zero and rms value SKAIMERR are added to the initial aiming direction of the gun For most guns this error is more important than the dispersion in the launch direction 2 SAM Propulsion and Guidance The SAM must now be flown out to intercept As discussed in the general description the time step must be shortened if any accuracy of flight is to be achieved The propulsion and guidance system used in RJARS is a hybrid system in which propulsion is applied along the body axis of the SAM and the heading and pitch are steered directly from the tracker or seeker with a lag to approximate the missile dynamics The SAM propulsion system is contained in the subroutine SAMACC This subroutine implements the equation ACCEL THRUST - DRAG MASS 33 All SAMs are modeled as four-stage devices--an unguided booster an interstage coast which may have zero duration a guided propelled sustainer and a guided unpropelled coast stage In each stage the thrust is constant zero for the coast stages and the mpss dpcreases linearly with time The thrust mass at the beginning of the stage and mass rate are library inputs All the SAMs on which we have collected data have used metric units so the thrust is in Newtons the mass in kilograms the mass rate in kilograms sec Factors of MTF meters to - 83 - feet appear in the equations to convert the acceleration to the English units used elsewhere in RJARS The drag is a function of the atmospheric density and the Mach number A subroutine ATMOS copied from ESAMS calculates the atmospheric density and the velocity of sound as functions of the SAM The Mach number is the ratio of the SAM velocity to the altitude velocity -f sound The drag force is DRAG 5 DENSITY REF AREA VEL MTF 2 CD 34 where the reference area is in square meters the SAM velocity in fps and CD denotes the drag coefficient For an actual SAM the drag coefficient is a function of Mach number the angle of attack of the SAM with respect to its flight path and the position of the guiding fins The latter two variables are not included in RJARS so the drag coefficient is treated as a function of Mach number only For almost any SAM the drag coefficient will be approximately constant at low velocity will increase rapidly as the velocity of sound is approached to a maximum for M the Mach number slightly beyond unity then will decrease again as the airflow around the SAM becomes smoothly supersonic The drag coefficients for the three stages will have approximately the same shape versus M but will have different numerical values We have found by studying an ensemble of SAMs that the drag coefficient is well fitted by a set of inverse quadratic functions of M 3 coast Let the three stages be denoted 1 boost 2 sustain The interstage coast uses the drag of the sustainer For each stage define three transition values designated MACHT in the program thereby forming a three-by-three array MACHT K L where K denotes the stage Then the drag coefficient is given by - 84 - CD CDI K L I CD2 K L M 2 35 If the Mach number is below MAC17T K l L 1 is used in Eq 35 if it is between MACHT K 1 and MACHT K 2 L 2 and if it is between MACHT K 2 and MACHT K 3 L 3 For Mach numbers above MACHT K 3 set the Mach number equal to MACHT K 3 thereby keeping the drag coefficient constant at high velocities The coefficient CDl is always positive For the booster CD2 l l 0 or a small negative value corresponding to the near constancy of the low velocity drag coefficient usually between - 4 and - 6 CD2 1 2 will be negative and is All others coefficients will be positive Actual calculation of the drag coefficient parameters may be done quite readily from a curve of drag coefficient versus Mach number the curve is generally provided with SAM data The SAM velocity and position are updated with a second-order Runge-Kutta equation The subroutine SAMACC which takes as inputs the SAM altitude and velocity is used with their values at the previous subdivided time step to calculate the acceleration at the beginning of the last interval pitch and heading The position is updated using the past velocity The velocity is then incremented with the calculated acceleration and the mass is decremented The new altitude velocity and mass are entered into SAMACC to obtain the acceleration at the end of the interval The velocity and position are then corrected yielding as final results the equivalent of allowing the acceleration to vary linearly over the subdivided time interval The direction and range from the SAM to the target are calculated During the boost stage no guidance is applied to the SAM so its heading is maintained constant the loft program The pitch decreases steadily following During sustain and coast for command guidance the aircraft and SAM paths are projected forward along their current headings to their point of closest approach The azimuth and elevation of the line of sight from the SAM to the position of the aircraft at its time of closest approach then determine the direction toward which the - 85 - SAM should be pointed Semiactive and IR SAMs use proportional navigation If the SAM is an artillery shell the flight is unguided acceleration and velocity are calculated as above The The pitch is corrected for the effects of gravity drop and the heading is maintained at its launch value The position is then updated Let S denote the vector from the SAM to the aircraft with present value S and let u vM - vA denote the relative velocity of the aircraft and the SAM Then the magnitude of the square of the vector S is given as a function of time from the present by S 2 S' - 2 SJ t u2 t2 36 This has a minimum at the time t s3u lu 2 7 at which the position of the aircraft with respect to the ground is given by 2 Al XAO y S u2 38 The SAM velocity vector is commanded to point along the vector from the SAM to the position XAl However a true SAM could not execute such a command which requires instantaneous velocity changes since it can only apply finite accelerations using its fins or thrust vector controls To simulate the situation without requiring excessive complication the dynamic response of the SAM has been approximated by a simple lag response characterized by the library input TIMECON Thus the SAM heading H responds to the commanded direction A the azimuth of the line to the projected point described above by the differential equation - 86 - TIMECON dHldt H A 39 The direction A is assumed to vary linearly with time from the beginning to the end of the subdivided time step With this approximation the solution of Eq 39 expresses the heading at the end of the interval in terms of the heading at the beginning of the interval the commanded azimuth at beginning and end and three lag parameters H t UTG H t LAGCON l A t LAGCON 2 40 A t DTG LAGCON 3 where the three lag parameters calculated during data input are given in terms of the time constant by X DTGiTIMECON 41a LAGCON 1 exp -X 41b LAGCON 2 1 - EXP -X X - EXP -X 41c LAGCON 3 I - I -exp -X X 41d This guidance system is a modified form of lead pursuit guidance The information about the aircraft position comes from the tracking system in terms of the variables ACLATI ACLONGI ACALTI so it is already corrupted with tracking errors The SAM will stage itself at booster cutoff enter state S - sustaining and at sustainer cutoff enter state C - coasting If the flight time exceeds the maximum flight time available to the SAM it will self-destruct and so announce Semiactive and IR SAMs employ proportional navigation for which the commanded rate of change of heading is proportional to the angular change of the line of sight from missile to target The proportionality - 87 - constant SMGUIGAN is stored in SMLIB for each missile type The equations may be integrated once yielding the change in heading during a subdivided time step in terms of the commanded change and the SAM lag constants Because of the higher order equations an additional lag constant appears in the expressions Proportional navigation systems are well known to be subject to instability in the final approach stage if the gain is too high The problem is alleviated by making the gain a function of the time to go This has not been implemented in RJARS but if the closing velocity is high the effect should not be too important 3 Semiactive Seekers The semiactive and IR seekers are updated in UPDSM seeker is a monopulse radar receiver four antenna system The semiactive Briefly it is simulated as a One pair of antennas is displaced in the horizontal plane the other in the vertical Antenna patterns are calculated using the subroutines SEKRPAT which finds the pattern of an individual antenna taken to be the pattern of a horn antenna rather than a paraboloid and MONOPAT which assembles the patterns of the four oriented and displaced antennas The sum of the four outputs SKSUMSIG is used to find the total returned signal The combined signal from the two right displaced antennas is compared to the signal from the two left antennas If it is greater then the target should be to the right of the antenna vertical midline Similarly the signal from the upper antennas is compared to the lower pair to find if the target should be above or below the horizontal midline These signals designated SKDIFFSIG O and SKDIFFSIG l are divided by the sum signal and properly scaled to provide azimuth and elevation input commands for the guidance system The scaling is established in the opening GETDATA section of RJARS by finding the values of command signal produced by 01 degree displacements The subroutines ORIENT and REORIENT respectively convert the angles from inertial space to the nominal sight line from target to missile and back onopulse seekers are generally limited to about a beamwidth of coverage since outside that value the correction - signal has the wrong sign 88 - This effect is included in RJARS The beamwidth is that of the seeker and may be considerably wider than that of the tracker 3a Seeker Clutter RJARS first calculates the signals as if the seeker were aimed perfectly at the target It then looks at the effects of clutter Clutter in a pulse doppler or CW system is more complicated than is the clutter treatment in a pulse radar system clutter follow those of ESAMS The procedures used to treat For clutter to affect a pulse doppler system mounted on the seeker the following conditions must be satisfied I The clutter signal must lie within the range gate of the seeker Thus the path length from tracker to clutter region to missile may differ from the path length from tracker to target to missile by less than the range gate width Since a constant value for the sum of two such lengths corresponds to an ellipse this condition defines a pair of ellipses on the ground 2 The clutter signal must lie within the doppler filter width around the signal doppler frequency The doppler frequency of the clutter signal is determined by the aircraft and SAM velocity which set the rate of change of the two path lengths Since the two lengths involve the coordinates of the ground point with opposite signs there results a condition on the difference of the two path lengths A constant value for the difference of two such lengths corresponds to a hyperbola so the ground point must lie between two hyperbolas 3 The clutter signal will lie in the doppler filter band if the doppler frequency produced by the path difference differs from the target doppler frequency by a multiple of the pulse repetition frequency Consequently there will be a set of paired hyperbolas on the ground which can produce clutter - 89 - signals These may extend out to the horizon of mutual visibility 4 The range gate width and doppler filter width are generally small enough that the ground properties do not change appreciably over the ground regions allowed by conditions 1 and 2 Thus two ground points can be located determined by the possible intersections of the ellipse and hyperbola at the center of the regions The effective area of each ground region can be calculated analytically by approximating it as a parallelogram 5 The ground points must now be tested for visibility to the tracker the missile and the target Since the position of the missile is not known prior to the simulation this calculation cannot be performed by the preprocessors but must be made at each subdivided time step during the missile flight The subroutine MASK performs the detailed calculations which are essentially the same as those described earlier in UPDTR If the ground points are visible to both the seeker and the target the seeker antenna gains in the proper directions are used to find the clutter signal from each point The sum and difference signals of the clutter are combined with those of the target to find the net input signal to the guidance system The appropriately weighted signals from all visible hyperbola pairs must be included While seeKer clutter occurs rather infrequently because of the severity of the conditions above when it does occur the effects may be quite severe and cause the seeker to lose lock on the target Clutter in a CW seeker is a somewhat nastier problem range gate so the ellipses do not limit the clutter region There is no The clutter must be integrated over the region between each pair of hyperbolas out to the visibility limits Each ground point between the hyperbolas must b e weighted by its area which involves the distance from the midline of the hyperboia the angle bisecting the asymptotes and by the antenna pattern in the proper direction This calculation is - 90 - quite complex and significantly slows the RJARS operating speed the moment CW cluLter is commented out of RJARS At When the theory is improved the effect will be restored While clutter effects on seeker5 are quite complex the effect of multipath should be negligible For a seeker to be affected by multipath not only must the return meet the conditions above but the ground regions must include specular reflection points The probability of this occurring is sufficiently low that seeker multipath effects are not included in RJARS 3b Jamming of Monopulse Seekers Jamming effects on monopulse seekers are considered The usual technique for jamming a pulsc doppler seeker is velocity gate pull off in which the jammer generates a signal at a deceptive doppler frequency varies it in time to cause the velocity gate to move away from the target doppler velocity then turns off the deception signal tu leave the seeker hanging in limbo timing of ti- A more sophisticated version varies the l'eception signal so the range gate is also deceived RJARS does not handle this procedure but includes it under range and angle deception of the tracker if desired simulation of velocity gate pull off is fairly simple The effect of decoy deception of seekers is included When a decoy is present the combination of target and decoy signals weighted acccrding to their relative strength is used to get the net sum and difference signals for guidance input The reflected and radiated signals are included as the variables SKINTERF 0 and SKINTERF l1 The effect is to cause the seeker to follow the apparent center of radiation which it is boped lies close to the decoy The target and decoy signals are proportional to the antenna patterns in their respective directions Since only the motion of the seeker direction is controlled these patterns must be evaluated from tne predicted position of the seeker from its last position and the seeker servo equations This effect can tend to make the seeker wander between the two sources rather than lock on one of them - 91 - As the missile approaches its target the angular separation between the target and the decoy increases until only one of the' is in the seeker field of view At that point the seeker should snap to the direction of the remaining signal limited by its rate of servo motion For typical seeker beamwidths and decoy separations this event will usually not occur until the last 1000 to 2000 feet of travel 4 Infrared Seekers Infrared guided SAMs operate very similarly to semiactive SAMs The launch procedure requires that the seeker actually be locked onto the target Since IR SAMs are generally pointed by optical equipments the relative sensitivity of the IR and optical determines whether the SAM has to wait a long time after being aimed until the seeker locks on Once the SAM takes off it uses the onboard seeker to provide the angular information for the proportional navigation guidance system The maximum angular rate capability of the seeker is a function of the received signal level will not move For signals below the minimum level the seeker Above the upper critical level the seeker can move at its maximum rate In between the seeker rate is limited to an amount proportional to the signal level The critical levels and maximum rate are stored in SMLIB The rate of response of a seeker is usually very fast so it moves to the center of radiation of the received IR energy The resulting pointing direction is transmitted to the guidance system clearly can be decoyed by flares Such a system RJARS has adapted the ESAMS flare treatment 4a Flares Only a single type of flare is provided in RJARS changed if data on other flare types become available This may be Each airplane can have zero one or two flare dispensers the number and dispensing pattern being governed by the variable ACFLPAT for each aircraft in the scenario The position of each flare dispenser is displaced longitudinally along the fuselage midline from the aircraft center and - 92 - laterally perpendicular to the midline midline A single dispenser is along the Dispensers are tilted with respect to the vertical and pointed in an arbitrary azimuth direction If there are two dispensers they have the same tilt from the vertical and symmetric azimuth The number of flares in each dispenser is specified in the variable ASLFLAREO stored in IRLIB for each aircraft type same number of flares in each dispenser Flares are dispensed with a constant time separation Two dispensers may fire simultaneously or alternately If the latter a random draw at the beginning of the simulation determines which dispenser fires first The data on flares are stored in IRLIB The flare brightness is given as a lookup table against time and flare velocity Its mass and drag coefficient are given as a separate lookup table using the same variables but with different values for the time and velocity arguments Flare radiation is treated as omnidirectional and the attenuation factor for the two bands is stored for the same values of range as used for the aircraft attenuation data The decision to launch flares in RJARS is reactive Two numbers are stored for each aircraft in IRLIB representing the probability of detecting a missile launch from nose-on or tail-on incidence The nose- on probability is derived from discussion with pilots resident at RAND the tail-on probability from some consideration of the capabilities of IR missile warning detectors The detection probability is fitted with a cosine function in azimuth between the nose and tail values and a cosine of the elevation angle to partially account for the obscuration of the line of sight When the IR missile is launched a random draw determines if the aircraft is successful in detecting the launch and the result is printed If the detection is successful the aircraft begins dispensing flares according to its specified pattern The probability of successfully launching each is determined by a random draw against IRFLREL the reliability of launching and lighting the flare If successful the flare is released with an initial velocity with respect - 93 - to the aircraft IRFLVEL in the direction set by the tilt and azimuth of the dispenser These variables plus the time separation of flares IRFLINT are stored in IRLIB The flare is flown by the subroutine FLYFLARE which operates every subdivided time step DTG The drag coefficient stored versus time and velocity is actually the product of the true drag coefficient and the area of the flare FLYFLARE flies the flare like an unguided SAM interpolating in the lookup tables for mass and drag coefficient and updating the velocity and position The characteristics of flares are usually such that they decelerate rapidly and fall behind the aircraft If the tilt and azimuth angles are properly chosen forward flying flares can be simulated 4b Signal from Target and Flares The IR radiation in each spectral band is calculated from the lookup tables knowing the flight time and the velocity signal at the seeker received from each flare This gives the RJARS contains a rudimentary scheme for determining whether the flare is received or rejected by the seeker The flare travels and is observed for a time SKFLRJCTTIME during which it is affecting the seeker After that time a random draw against a number SKFLRJCTPROB ascertains if the flare is accepted or rejected The time and probability are stored in SMLIB for each IR missile type A better scheme would be to use either the kinematics of the flare or the spectral properties of its radiation for the rejection process Since we do not have data on either of these we have resorted to the overly simplified process just described The numbers for time and rejection probability at present in SMLIB are quite arbitrary and any conclusions based on them should be taken cum grano salis If the flare is rejected by the seeker it continues to fly but its radiation does not affect the seeker If it is accepted the seeker now has as inputs the radiation from the target and the flare The weighted sum of the angles to each sets the pointing angle of the seeker toward the center of radiation If either the target or the flare moves outside the field of view of the seeker its radiation is set to zero - 94 - Most often a flare is brighter than an aircraft and the seeker is decoyed The aircraft continues to release flares following its specified pattern at the time separation IRFLINT infrared flare interval Each flies until it burns out at the end of its flight interval set by the length of the lookup tables for drag and brightness used in RJARS this duration is six seconds rejection test For the flare type Each flare undergoes the The seeker will point toward the resultant center of radiation of the signals from the aircraft and all the accepted flares each at its proper flight time flares from each aircraft An index ASNFLARE marks the number of A subroutine KILLFLARE tests if the flare has reached the end of its burn time or has hit the ground If it does either the index of any other flare from that aircraft is decremented the nature of the dispensing ensures that the burnout of flares is sequential with index The SAM flight continues until the endgame is reached 5 Endgame SAM flight data are printed out under the options SMPRNT and IPG If SMPRNT 1 then detailed flight data appears at each IPG'th subdivided time step Otherwise the SAM state and range to its launcher and target are printed each time step When the range to the target is less than 1000 feet the detailed data are printed every subdivided time Printed quantities are listed in the user's section step The SAM continues its flight until any of several conditions is met 1 Its range from the launcher exceeds the range of the aircraft from the launcher This is usually the final condition when the following tests are not met 2 The range from the SAM to its target or the partner of its target is less than the fuzing range SMFUZRNG and the range to the closer of the indicated objects is increasing range is stored in SMLIB The fuze - 95 - The SAM uses IR guidance and the seeker has lost lock on its 3 target The target may change during the flight When any of these tests is passed the endgame flag SMENDFLG is set and the position of the SAM is interpolated backwards along the last segment of its flight to determine the time and the coordinates of the point of closest approach to the true position of the aircraft The flight of the SAM has used imperfect radar data but to this point has been treated as following its guidance system perfectly Guidance errors are now simulated by adding a random vector to the miss distance vector The magnitude of this vector is normally distributed with a standard deviation equal to the input value SMCEP and the direction of the vector is uniformly distributed over the unit sphere If the SAM is a shell the SMCEP stored in SMLIB is actually an angular dispersion and it is multiplied by the range to give the displacement SMCEP In either cdse the resulting magnitude of the miss distance is then calculated The aircraft is approximated as an oriented ellipsoidal fuselage with flat elliptical wings The fuselage is circularly symmetric around the body longitudinal axis with an elliptical side view with major axis ACLENGTH and minor axis ACFUSDIAM The elliptical wings have major axis ACSPAN and minor axis ACWINGCHORD All these dimensions are stored in ACLIB If the location of the miss distance calculated above is within the fuselage or wing a direct hit the kill probability is set to unity When a suitable model of kill probability versus hit probability becomes available it will be incorporated in RJARS SAMs with contact fuzes can kill only with a direct hit For those SAMs with proximity fuzes the endgame kill probability in RJARS is assumed to be a function of the magnitude of the miss distance from the nearest critical point on the oriented aircraft Warheads generally produce both blast and fragmentation effects so the kill depends on the orientation of the vulnerable components of the aircraft An attempt to simulate these effects leads to great complications see Ref 6 pp 158-204 At present the kill probability versus distance is taken to - 96 - depend on the SAM type but not on the aircraft type and the angular dependence of the kill probability has been dropped The kill probability is the product of the probability that the warhead detonates library input and the probability a kill is achieved if it does detonate At close distances below a range KRMIN blast effects are so strong that the latter probability is unity At great distances beyond a range KRMAX the kill probability is zero We have approximated the kill probability as a linear function of range between KRMIN and KRMAX both library inputs This type of relation is consistent with test results on various SAMs The calculated kill probability is compared to a random draw to determine the outcome of the endgame and stored for the summary The success or failure is printed If the kill is successful the aircraft's flag ASDEAD is set to zero which removes it from the simulation Otherwise the SAM enters the F or refire state for another shot The number of missiles available at the state is checked as described at the beginning of this section If a radar-guided SAM has been deflected to a decoy and kills it the aircraft will release another decoy as long as there are still decoys on board The launcher will think it has missed the target and will begin to count down another SAM The decoy identification number is incremented to make clear to the summary just what has happened If an IR-guided SAM is deflected to a flare it will kill it leaving the aircraft unscathed Flares still in the air will zontinue to fly until they burn out or crash If available a new SAM will begin countdown and it is assumed to be unaffected by flares until it launches possibility that the optical observer associated with the SAM can identify flares has not been implemented The - 97 I - UPDWR--UPDATE WARNING RECEIVERS The warning receivers in RJARS are used to establish whether the aircraft is detecting the radar and whether the jammer on the aircraft should be turned on or off The receiver contains WRNBAND frequency bands each of which has an upper and lower frequency limit and a receiver sensitivity WRBSENS Most airborne warning receivers use multiple antennas to achieve coverage without scanning provides coverage in a particular direction Each antenna The signals from the several antennas are combined and the resultant displays gain without scanning The combined pattern is approximated by a rosette antenna pattern which contains WRNLEAF lobes All lobes have the beamwidths WRNHB and WRNVB in the horizontal and vertical planes and are offset by an angle WRDIP in the vertical plane The first lobe is offset from the forward direction by an angle WRBS and the succeeding lobes are centered on directions displaced from the first by multiples of an angle WRPHIN 360 WRNLEAF 1 Power Calculations A flag WROUTBFLG determines if a radar lies within the frequency coverage of the warning receiver If this flag is set then that receiver ignores that radar thereafter Otherwise at each time step the receiver on each aircraft checks the signal from each radar that is transmitting is within the horizon and is within the maximum range of the radar against that aircraft The last choice is to ensure that the jammer will not be turned on if the radar cannot detect the aircraft The power from the radar is calculated from the equation ERP R Gw C 2 SDL RW 42 2 F2 R2w 47C R RRW where GW is the gain of the warning receiver antenna in the direction of the radar SDL R the sidelobe level of the radar in the direction of the receiver RRW the range from the radar to the receiver and the - 98 other symbols are familiar - For search or acquisition radars the sidelobe level is set equal to unity corresponding to the time at which the radar scan sweeps over the receiver For a tracker pointing at the selected aircraft the sidelobe level is again unity but for a tracker pointing at some other aircraft the appropriate sidelobe level must be used The gain of the receiver antenna is calculated from the rosette pattern The received power from Eq 42 is compared to the receiver sensitivity in the proper frequency band Receiver sensitivities are customarily expressed in decibels with respect to one milliwatt dBm and RJARS adheres to this conversion In reality many radar pulse trains may simultaneously be incident on the receiver and the separation of these trains and identification of signals is a very difficult task RJARS ignores these high density environment problems and assumes that the several signals are immediately identified This is a possibly significant limitation in the model One resolution might be to provide a delay in identification that is proportional to the number of signals received Another is to allow for saturation of the receiver by limiting the number of signals it can accept in any frequency band Still another is to limit the number of pulses per second that can be handled thereby limiting the number of radars with special provision for high repetition rate pulse doppler transmitters These are all possibilities for future expansion of RJARS 2 Receiver Decisions After the comparison with the sensitivities there are a number of possibilities the radar A flag WRRDFLG marks whether the receiver has detected WRRDFLG has as arguments the aircraft identification number and th radar identification number so there is a flag for each aircraft-radar pair For simplicity the variable will be used without citing the arguments If WRRDFLG 0 and the received power is below sensitivity then the undetected radar is still undetected and nothing - 99 - need be done Also if WRRDFLG 1 and the received power exceeds sensitivity then the catalogued radar is still being detected and again no procedure is necessary If WRRDFLG 0 and the received power exceeds sensitivity then the receiver has detected a new radar It adds one to the running count of radars detected in that frequency band sets the flag WRRDFLG to 1 and sets WRBID the array item that tells the receiver which radar it is dealing with to the radar identification number this radar type is one that it should jam It then checks if If true then if the radar is a long-range searcher or if it is an acquisition or track radar either pointed at the aircraft itself for aircraft that are not members of a group or pointed at itself or a member of the aircraft's associated group then the subroutine WRJMON is called to begin jamming the radar If the flag WRRDFLG 1 and the received power is below sensitivity then there are further possibilities If the radar is a search or acquisition radar then the parameter INBEAM is checked to ascertain if the radar has swept over the receiver during the last time step If it has not then the situation is only temporary and the receiver does nothing If it has or if the radar is a tracker then either the radar went off the air or the aircraft went over the horizon or beyond detection range If the radar is off the air the receiver and jammer should be turned off a task performed by the subroutine WRRECOFF The program calculates receiver power only for those radars which are not over the horizon If the received power has dropped below sensitivity while the jammer is on as could happen if the radar is a tracker aimed at another member of the aircraft's group so the aircraft is in the sidelobes of the radar transmitting antenna then also the receiver and jammer should be turned off If the radar and aircraft are mutually masked by terrain then the jammer should be turned off regardless of the received signal - 100 3 Jammer Decisions The subroutine WRJMON is called when the receiver is turned on or when the aircraft joins a group that is jamming the radar WRJMON first checks that the radar is within the frequency coverage of the jamming transmitter and if so selects the proper band It then determines what is the most effective jamming technique to use against that radar and looks at its own stable of techniques to find if the desired technique is available If so that technique is the jamming tactic to be employed otherwise barrage noise is radiated The jammer flag JMRDFLG is set signifying that particular radar is being jammed the count of radars in the band being jammed is incremented and the identification JMBID is set to the radar number The jammer antenna is approximated by a rosette just like the receiver The parameters of the rosette will be different For those jammers that use fixed antennas the actual combined rosette pattern will be used For those jammers that scan the antenna and track the target the number of leaves of the antenna is set to one In such cases the power radiated by the jammer is emitted as if the jammer antenna is pointed directly at the radar corresponding to accurate measurement of the angle of arrival of the signal followed by steering of the jammer transmitter antenna If the jammer antenna gain is low then the situation could also correspond to a broad antenna beam which encompasses the radars being jammed or even an isotropic transmitter Note that the ERP of the jammer should be interpreted as the product of the on-axis antenna gain and the power input to the antenna including line and reflection losses RJARS divides the power available in a given frequency bond equally among all the radars in that band that are being jammed at a given time A priority designation would be desirable but has not been implemented The subroutine WRRECOFF turns the receiver and jammer off when called It first identifies which position in the count of signals in that band is occupied by that radar The positions are determined by the sequence in which the radars were detected Those radars that occupy higher positions are each lowered one position and the now vacant - highest position is dropped flag is turned off 101 The count is decremented and the receiver The subroutine WRJMOFF is then called to apply the same procedures to the jammer The event information is printed UPDWR is the last calculation routine called during the simulation run After its completion the time is incremented and the procedures repeated until either the final time is reached or there are no surviving aircraft the possibility of no surviving radars is very unlikely If it were to occur the aircraft would simply continue flying until the time is up At the simulation end the subroutine output is called to print the summary of the run J OUTPUT--PRINT 1 Print Sequence SUMMARIES OUTPUT first identifies which run in the Monte Carlo sequence is being printed It then prints the search radar summary specifying the behavior of each search or acquisition radar against each aircraft The number of looks of the radar at the aircraft number of hits successful detections and their ratio is printed giving a measure of radar and also jammer effectiveness Each time and range of entry or exit of the aircraft into the field of view of the radar is printed there may be many if the aircraft is frequently masked by terrain and the time and range of each detection and loss of detection Finally the average number of radars pointed at each aircraft as determined by the number of times radar beams passed over the aircraft divided by the number of time steps is presented The second summary pertains to trackers For each tracker aircraft combination which actually occurred the parameter RTITK counts the number of times a tracker was assigned to an aircraft the times of assignment turning-on and turning-off of the acquisition radar and turning-on and turning-off of the tracker are printed The anomalies described in the earlier version of RJARS have been corrected All times are properly initialized and updated each time step so all printouts are consistent It is still possible for the acquisition radar to turn the tracker off without its ever having been on If this - 102 occurs the tracker on and off times are the same as the acquisition off time After the trackers the summary of the SAMs is printed For each SAM which reaches the launch state the identification of the launcher the list number for that SAM among the several SAMS fired from that launcher the target aircraft the launch time and the launch outcome success or failure is printed If the SAM is decoyed the identification number of the decoy is printed If the SAM crashes or loses tracking during flight that result and its occurrence time is printed If the SAM performs an interception the time range from the launcher miss distance kill probability and outcome MISSED TGT or SHOT TGT DOWN are printed Following is a box score showing the number of SAMs launched launch failures number losing track number of misses and number of kills Next comes a summary on the anti-radiation missiles For each ARM or each aircraft its identification and whether it has been launched YES NO is printed For those that have been launched the launch time target radar and flight result LOST TRACK REACHED TGT are printed If the ARM reached the target the kill time kill probability and outcome MISS KILL are printed on board this summary is omitted If there are no ARMs If there are no ARMs on any aircraft the header is omitted The following aircraft summary shows for each aircraft if it reached its destination if it was shot down on ingress or egress and the time of each event The surviving aircraft may still be in the field or may have escaped safely The appropriate expression is printed For each aircraft its number of engagements with SAMs is printed A box score shows the number of aircraft that entered the field number shot down on ingress number reaching destination a measure of mission effectiveness number shot down on egress number still in field number escaped total number of engagements with SAMs and the average number of SAM engagements per aircraft - 2 103 - Statistical Calculations If the RJARS simulation is in cooperation with a JANUS operation statistics on the aircraft survivability are collected in OUTPUT and prepared for transmission to JANUS Even if JANUS is not used these statistics may be of interest to the user The decision to collect these statistics ib controlled by the flag IJANUS 1 collect 0 do not collect The statistics are contained in the structure PRDBN The concept behind the probability distribution is that the aircraft interact with the ground defenses in a sequential manner An aircraft enters the operating region of a defense flies through it and is either killed or escapes There may be several shots at the aircraft from a given launcher determined by launch success and kill probability Thus there is a time interval for the aircraft and defense to interact and a smaller time interval within which a kill may be achieved For each interaction on each iteration the kill time if any is stored At the end of the simulation JREP NREP the earliest and latest kill times for each interaction determine the start and end times of the killing interval To a reasonable approximation the kill probability density is unifoim over this interval The set of intervals together with the kill probability per interval is calculated for each interaction and stored for transmission to JANUS If the defensive system is dense several elements may be shooting at the aircraft at the same time The corresponding kill intervals will overlap and the resultant kill probability densities are additive for the overlapping times Also there may be more than one interaction interval between an aircraft and a defense All such intervals are recorded separately The data transmitted from JANUS via CAGIS to RJARS contain Lwo times designated LOSI and LOSN The first is the time at which an aircraft can first perform its mission the second the time at which it leaves its target area initial data The times are located in the flight planner as The JANUS operators were interested in the kill probability before LOSI which gives the likelihood that an aircraft was killed on ingress the detailed intervals between LOSI and LOSN and the - 104 - kill probability after LOSN the egress kill probability All these quantities are calculated and transmitted When the OUTPUT subroutine has printed the summaries the Monte Carlo subroutine UPDMC is called to determine if the run should be repeated If the last run has been completed the program prints RJARS is finished and stops Otherwise the program flags and variables are returned to their initial values except for the random number generator whose present value is printed ait the beginning of the next run K RJARS then executes another simulation CALCSR--AUXILIARY-CALCULATIONAL SUBROUTINES RJARS contains seven mathematical subroutines UNIV NORMV RECT SPHER LINSGHT TRINDEX and ZTERN The subroutine UNIV is the random number generator which produces a variable YFL that is uniformly distributed between 0 and 1 congruence principle Al UNIV operates on the multiplicative A number XR is multiplied by a fixed multiplier The product is divided by a number Ml and the remainder is taken as the next value of XR XR begins with an input value SEED and is permitted to take on only odd integer values The product XR Al will usually exceed the value of Ml and the remainder after division should be uncorrelated with the previous value of XR Thus the values of XR should be uniformly distributed over the range 1-M with no correlation between successive values Dividing XR by Ml produces YFL uniformly distributed between 0 and 1 231 In RJARS the value of Ill is 2147483647 1 the largest number that can be carried on the BM-3033 operating at RAND and Al 62089911 a number that produces a sequence of maximum length and minimum correlation between successive values This choice of parameters should produce a sequence approximately 228 in length before a repetition is likely Ml 4 is the theoretical value half that because of the limitation to odd values enough fo This should be long practical purposes The subroutine NORMV uses UNIV to calculate two independent normally distributed variables of mean zero and variance 1 derived as follows Let X and Y be the two variables probability density is It is Then their - 105 - P X Y exp - X 2 y 2 12 27 43 with R and 0 the polar coordinates corresponding to X and Y their probability density is P R E R exp -R 2 2 27c 44 thus the phase is a random variable uniformly distributed over the range 0-2r and the amplitude has a Rayleigh distribution The cumulative distribution of R that is the probability that R exceeds some value A is W A I - exp -A 2 45 2 The variable exp -A 2 2 thus is uniformly distributed over the range 0-1 since that is the character of a cumulative distribution The normally distributed variables are calculated by inverting the procedure that led from Eq 43 to Eq 45 Thus call UNIV then set VAR1 a calculation variable equivalent to A to the value VAR 1 sqrt -4 60517 LOG 1O YFL 46 Since LOG10 is the only logarithmic base used elsewhere in RJARS we did not add the natural logarithm to the built-in mathematical functions list This is a residue of the PL-I origin for RJARS Then call UNIV again and set the variables VAR2 and VAR3 corresponding to X and Y to - 106 - VAR 2 VAR 1 cos 2 PI YFL 47a VAR 3 VAR 1 sin 2 PI YFL 47b This pair of independent normally distributed variables is used in the numerous calculations of errors The subroutine RECT which has been copied from JARSM with minor correction converts from earth-centered latitude-longitude coordinates to rectangular coordinates in the plane tangent to the earth's surface at the center of the coordinate system The inputs to RECT are latitude and longitude in degrees minutes seconds and hemisphere the outputs are the rectangular coordinates in nautical miles App B of Ref 2 The derivation is in If P is the point in question R the reference point then the rectangular coordinates X Y are given in terms of the latitude and longitude of P and R by the equations 48a X 3440 cos Lat P sin Long P - Long R Y 3440 sin Lat P cos Lat R 48b - cos Lat P sin Lat R abs cos Long P - Long R The coefficient 3440 is the earth's radius in nautical miles All calculations in JARSM and RJARS are performed in the rectangular coordinate system When the inputs are in the global latitude-longitude system RECT and Eqs 48a and 48b are used to convert the input aircraft and radar positions to rectangular coordinates RJARS can handle both input and output in both coordinate systems The choice is established by the parameter COORD also used in JARSM which here takes on the four values COORD 1 Input and output rectangular COORD 2 Input and output global COORD 3 Input rectangular output global - COORD 4 107 - Input global output rectangular To convert from rectangular to global a subroutine SPHER is used which inverts Eqs 48a and 48b The process leads to a quadratic equation whose roots are y COS Lat R ± sin Lat R sqrt 3440 2 - x2 - Y 2 1 3440 49 The inverse sine of these values is calculated and the one that is closer to Lat R is the latitude of the point P The longitude is then given by Long P Long R asin X 3440 cos Lat P 50 The latitude and longitude as outputs are expressed as degrees and decimal fractions of degrees Finally the calculational subroutine LINSGHT calculates the range azimuth and elevation of an aircraft from a radar It takes the coordinate differences DX DY DZ and converts these to spherical coordinates centered at the radar If terrain is not used or if the aircraft is indicated as visible to the radar by the terrain model if the terrain details are derived from maps the aircraft may be indicated as visible when it is actually below the curve of the earth LINSGHT determines if the aircraft is over the horizon and sets the flag RDACOH TRINDEX identifies the indices of an element in the terrain file TERRA when its location is given Each coordinate of the element measured from the origin of the rectangular coordinate system or LATO LONGO for the global coordinate system is divided by the terrain element size in that coordinate direction The terrain elements are centered on integral values of the indices and extend half an element length in each direction The magnitude of the quotient is compared with the greatest integer contained in it If the remainder after - 108 - comparison is less than 5 the integer equals the index magnitude the remainder exceeds 5 the next greater integer is used If The value of the integer after this decision is multiplied by the sign of the coordinate to give the correct index value The subroutine ZTERN calculates the terrain height at any position in the field It first uses TRINDEX to find the indices of the terrain element in which the point lies The normalized displacements x and y from the center of the element are found by subtracting the coordinates of the center from the coordinates of the point then dividing by the appropriate element length The height of the terrain surface is fitted by a quadratic expression that uses the element and its eight neighboring elements in question Let i and j be the indices belonging to the point Let z be the height at any index point a function of the indices and h be the height at the field point Then h is given by the equation H z ij z i I j - z i - I j x 2 51 z ij l -z ij - 1 y 2 z i 1j -2 z ij z i - 1j x 2 2 z ij 1 -2 z ij z ij - 1 y 2 2 z i Ij 1 - z i Ij -1 - z i - 1j 1 z i - 1j - 1 xy 4 In this expression the first term is the contribution from the center the second and third represent the terrain slopes in the two directions the fourth and fifth represent the terrain curvature in the two directions and the last corresponds to the orientation of the principal axis of the ellipsoid that has been fitted to the terrain Alternatively the second through the fifth represent the nearest axial neighbors of the element and the last the asymmetrical interaction of the nearest diagonal neighbors If a point within a border element of the terrain is to be treated this equation would overrun the terrain - 109 - array which is why no aircraft or radar can be permitted to be within a border element At the beginning of the simulation RJARS builds a rim around the apparent terrain border to avoid this problem Besides these mathematical subroutines CALCSR contains a number of the calculational subroutines referred to in other sections Descriptions of these subroutines follow The subroutine ORIENT takes two directions in inertial space and finds the angles between the second and the first Thus it finds the offset angle of a seeker from its boresight angle The mated subroutine REORIENT combines the angle from the second to the first with the inertial coordinates of the first to find the direction of the second vector in inertial space The subroutines SEKRPAT and MONOPAT find the patterns of a monopulse antenna as described previously The subroutine FACE starts with two points on the ground It finds which terrain elements are intersected by the line connecting the points The number of such elements and the length of the line in each element are found For each such element the terrain indices the coordinates of the midpoint of the connecting line and the type of terrain are indicated The subroutine CLUTTER uses FACE to find the relevant terrain elements For each the azimuth and elevation to the radar are found self-shadowing is determined and the cross-section per unit area is calculated from the fundamental terrain properties the radar frequency and the angle of incidence The subroutine RESPNS finds the gain for a monopulse antenna in the direction of the clutter point when it is aimed at the target The subroutine POWER finds the total return from a clutter element into a monopulse seeker using the geometry and RESPNS The subroutine ISORAD locates the ground points that satisfy the conditions for pulse doppler clutter and finds the effective area of the clutter regions - 110 - The subroutine MASK ascertains if two points are mutually visible The subroutine RIDGES calculates the locations of the successive ground entries to and exits from visibility providing the range and depression angle of each such point and the total number thereof The subroutine RIDGTEST takes a given range and azimuth and ascertains if the ground is visible to the radar at that range and azimuth The subroutine MULTIP calculates the multipath effects using many local variables First FACE is used to find the terrain elements between the target and the radar Self-shadowing is checked and RIDGTEST determines if the element is visible to the radar if the aircraft can see the element MASK finds If both can see the slope of the ground at the point along the connecting direction is calculated from the terrain data The angles of incidence of both rays with the element are found and tested for positive grazing angles with respect to the local slope The directions at the edges of the terrain element are found and the location where the difference between the angles of incidence passes through zero is ascertained if such element exists The specular point will be in that element The reflection coefficient at that point is found in terms of the terrain parameters the roughness and the angle of incidence using Eq 21 For each specular point the path length in the element and the phase of the ray reflected by multipath relative to the direct ray are found yielding an effective complex reflection coefficient The gain of the antenna toward each element is found and the net signal real and imaginary components multiplied by normally distributed random variables to take care of the independence of the reflections is found for each element and summed to give the total multipath signal This completes the description of the analytical model used in RJARS The next section is a user's manual describing how to prepare files and operate the program - Ill - RJARS USER'S GUIDE IV RJARS is a non-interactive program that operates entirely from input files and delivers its output to the standard printout of the computer system and to the file for graphical display Consequently the initial task of the user is to prepare the input files As discussed these are of two types library files that contain equipment data and simulation files that provide the values of the variables associated with a particular run Most of this user's guide is devoted to a description of how the files are prepared There have been many changes in the files since the earlier version of this report Ref 3 The description parallels the previous work but it should be emphasized that only the current files can be used with the operating version of RJARS PREPARATION OF LIBRARY FILES We shall discuss the nine library files first in alphabetical order They can be prepared at any time and updated as information on additional equipments becomes available updated during a run lines Library files cannot be All library files begin with descriptive header Except where specifically stated all entries are separated by commas including a comma at the end of each line The library files are 1 ACLIB Aircraft performance data 2 ACRCS Aircraft cross-section data 3 ARLIB Anti-radiation missile data 4 IRLIB Infrared and optical data 5 JMLIB Jammer data 6 MCLUT Terrain properties 7 RDLIB Radar data 8 SMLIB Surface-to-air missile data 9 WRLIB Warning receiver data - 1 112 - Aircraft Parameters The first file ACLIB is new It contains the data that represent the physical properties of the aircraft mostly dimensions and acceleration capabilities plus some special radar cross-section data All the data are placed on a single line for each for helicopters aircraft type sequence An initial header line identifies the variables in In the order of their appearance on the line the variables contained in ACLIB are ACTYP Aircraft type integer ACNAME A character string naming the aircraft This variable is not used in RJARS but serves to relate the aircraft type to real aircraft The string must contain no blanks and be followed by a space ACTURNAC Maximum acceleration in the yaw direction during a turn g's ACPITACUP Maximum acceleration in he upward pitch direction g's ACPITACDN Maximum acceleration in the downward pitch direction g's ACLENGTH Length of the fuselage feet ACSPAN Span of the wings tip to tip feet ACFUSDIAM Diameter of the fuselage feet ACCHORD Chord of the wing at its root feet ACTAILAREA Area of the vertical tail sq feet ACROTORRCS Radar cross section of the helicopter rotor edge on horizontal plane dBsm ACSENSORRCS Radar cross section of a helicopter externally mounted sensor dBsm ACSKIDFUSE Height of the center of the helicopter fuselage above the skid feet - 2 113 - Radar Cross Section The second file ACRCS contains the radar cross section rcs data for each aircraft type The format has been modified from the earlier radar cross section file to include three dimensional data and variable resolution The first data line for each aircraft type includes four items ACTYP Aircraft type ACNAME See ACLIB ACRCSAZRES Resolution in azimuth of the rcs data deg ACRCSELRES Resolution in elevation of the rcs data deg The azimuth and elevation resolutions are independent and can differ from aircraft to aircraft but for any given aircraft type all the data corresponding to that resolution must be present Thus if ACRCSAZRES equals 10 degrees the rcs must appear for each elevation value at all of the azimuths 0 10 20 170 180 The data are arranged so a given line corresponds to a fixed azimuth beginning with zero at the nose and ending with 180 at the tail The values along that line give the radar cross section as a function of elevation at that 2 azimuth The units of radar cross section are decibels relative to 1-m dBsm The elevation steps in units of the elevation resolution beginning with zero elevation corresponding to observation from below and ending with 180 for observation from directly above The azimuth and elevation resolutions must each divide into 180 so an integral number of elements appear on a line For example if the azimuth resolution is 5 degrees and the elevation resolution is 10 degrees there will be 37 lines of data 180 5 1 with 19 entries per line If the data from which the file is derived do contain a full range of elevation there is no problem with data entry If as often occurs there exist only data in the horizontal plane of observation then that data should appear in the central vertical column of the rcs file and zeroes should appear in the rest of the table In such a situation the - 114 - variable NDOF in the scenario should be set to 3 to avoid misinterpretations RJARS will think the aircraft has a I sq meter cross section in directions other than the horizontal plane The variable in the data entries of ACRCS is the RJARS variable ACALPHA1 Radar cross section azimuth data only dBsm ACALPHA2 Radar cross section azimuth and elevation data dBsm 3 Anti-radiation Missiles The third file ARLIB holds the data on anti-radiation missiles It begins with two header lines to describe the variables Then for each missile type we first list a line that contains the name or description of the missile then a line with the following variables ARLTYP Number identifying missile type ARLNBD Number of frequency bands in receiver ARLVEL Velocity fps ARLRMIN Minimum operating range nmi ARLRMAX Maximum operating range nmi ARLTDLY Time to fly without guidance sec ARLLOFT Initial loft angle deg Next come lines for each frequency band of the receiver On each line are the variables ARLBDNO Number of the frequency band in question ARLBDLFR Band lower frequency limit MHz ARLBDUFR Band upper frequency limit MHz After all ARLNBD lines have been entered the next missile is entered Only five ARM types should be included in ARLIB be a serious restriction This is not likely to - 4 115 - Infrared Parameters It contains all the data that The next file is the new file IRLIB pertain to infrared and optical equipment It begins with six header lines that describe the data in the file The first data line contains the ranges IRRANGE at which attenuation data is stored There are six values on this line given in nautical miles and corresponding to 0 1000 5000 13000 30000 and 100000 feet The next two lines pertain For each the first entry is to the solar radiation and attenuation the solar amplitude in watts ster in the appropriate wavelength band IRSUNSTR and the next six are the attenuation of the solar radiation IRSUNATTN at the ranges indicated above Note that the attenuation in IRLIB is a multiplicative factor on the amplitude not a coefficient in an exponent Next is data on paint A header line indicates the variables Each line contains three variables--an index counting the types of paint the variable PAINT a two-character code and the reflectivity of that paint The last entry in the paint list must have index zero and PAINT type NR nonreflecting After another header comes a single line containing the values for the matrices SKYGND and EXTINCT that describe the attenuation of optical contrast with range There are four values for each corresponding to the two indices ISUMMER and ISEEING The extensive flare data follow First are two description lines the first showing that flare data is to appear the next identifying the three variables that follow on the succeeding line IRFLREL Flare launch reliability IRFLVEL Flare launch velocity fps IRFLINTVAL Interval between launches from a dispenser sec Next are flare brightness values After a descriptive line a line gives the 15 values of the variable IRBRITETIME the times at which the brightness of the flare is specified Another line contains the three v3lues of the variable IRBRVEL the velocities at which the brightness - is specified 116 - Then come 15 lines with three values each the values of the flare brightness IRBRITE as a function of time and velocity After a descriptive line specifying the bands are two lines with the values of the attenuation IRFLATFIN of the flare signal in each band at the usual specified ranges The flare mass and product of area and drag coefficient are given as functions of time and velocity in the next four lines After a descriptive line comes a line with the four values of IRCDTIME and the two values of IRCDVEL knots On the next line is the mass IRFLMASS kg at the four times and on the following line is the drag product IRFLCDS in the sequence two velocities at the first time two velocities at the second time etc This completes the flare data Next is a set of attenuation tables As discussed in the analysis section these tables and the following signal tables will be changed to incorporate a better propagation model After a descriptive line showing that attenuation tables are coming and a second describing the first spectral band is a set of five tables for five ranges with a descriptive line indicating the range preceding each table The tables give the values of the attenuation IRATNFAC as a function of elevation and azimuth at that range in that spectral band The data on a line are at a specified elevation with the first corresponding to observation from below and the last to observation from above in steps of 15 degrees The data on that line are the values of IRATNFAC in azimuth steps of 15 degrees from tail to beam It is assumed in the program that the attenuation in azimuthal directions between the beam and the nose is the same as at the beam so only half the full azimuth range need be covered Note the change in sequencing between radar data and IR data a consequence of historical precedent After the full set of data is listed for the first spectral band there is another descriptive line for the second spectral band and a corresponding set of attenuation data As discussed in the analysis section the same attenuation data are used for all aircraft a situation that will change in the future next set of entries in IRLIB following a single descriptive line The - 117 - pertains to the IR data for the various aircraft types For each aircraft type the first line contains a set of miscellaneous variables ACTYP Aircraft type ACNAME Descriptive string showing what is to follow See ACLIB for conditions ACNOSEDET Probability of detecting an IR target directly ahead ACTAILDET Probability of detecting an IR target direct behin1 ACFLTILT Tilt of flare launcher from vertical deg ACFLAZ Azimuth of each flare launcher from forward deg ACFLFUSDISP Longitudinal displacement of flare launchers from center of nose-to-tail line ft ACFLWINGDISP Lateral displacement of each flare launcher from center line ft ACLFLARE Number of flares per dispenser Two tables that follow give the aircraft radiated power in watts per steradian in each spectral band as functions of elevation and azimuth After a header describing the band the sequencing follows the attenuation tables except that the full range of azimuth is covered The entry item is the variable ACIRSIG The aircraft data as described complete the IRLIB file If an aircraft is called in the scenario and there are no IR data available for it RJARS will halt with an error indication to improvise data It may be necessary The accuracy of such improvised IR signal data cannot be confirmed by RJARS Remember if new values are to be inserted the numbers called for are watts per steradian not temperature It is only fair to note that much of the data in the working IRLIB file used at RAND have been found by interpolation from some very sketchy measured values - 118 - 5 Jammers The nexL file JMLIB contains the jamming transmitter data contairns a single header line to identify Nariables It Then for each jammer type the first line contains the information JLTYP Numiber identifying jammer type JLCODE 5-character code describing jammer JLNBAND Number of frequency bands in j-mmer JLRDTECH l 2 3 4 Array of 4 values each equal -o 0 i 2 3 or 4 listing jamming techniques available to the jammer If the value 1 appears in the array the jammer can perform search deception 2 tracking range deception 3 tracking angle deception 4 tracking range and angle deceptioi The variable JLRPTECH O is set internally to 0 so all jammers can radiate noise Data for each of the NJLBAND bands of the jammer follow exceed 20 NJLBAND cannot For each band line the variables are JLBNUM Number identifying band JLBCODE 3-character ccde describing band e g low JLBERP Effective radiated power W JLBLFRQ Lower frequency limit of band MHz JLBUFRQ Upper frequency limit of band MHz JLBBDW Bandwidth of radiated noise MHz JLBPOL Polarization loss dB positive value loss A blank line separates the last band lire of one transmitter from the fir5t line of the next This description pertains to JMLIB before the - 119 - inclusion of repeater decoys A file modification adds to the end of the first line the variable JLGAIN the gain of the jammer if it were used as a repeater set to unity For most jammers this variable is not used and is Also a recent modification adds at the end of the data line for each band the variable JLBREL the reliability of that band 6 Terrain Parameters Next consider the new file MCLUT This contains the properties of the ground used for clutter multipath and optical reflectivity After a descriptive header the data fof each terrain type are listed on its single line For the interpretation of the variables see the analysis The sequence of variables is as follows 7 TRPTYPE Index terrain type TRPCODE Terrain type description 5-character code TRPA Parameter A in terrain radar cross-section TRPB Parameter B in terrain radar cross-section TRPC Parameter C in terrain radar cross-section TRPD Parameter D in terrain radar cross-section TRPROUGH RMS roughness parameter cm TRPEPSR O Real part of dielectric coefficient dry TRPEPSI 0 Imaginary part of dielectric coeff dry TRPEPSR 1 Real part of dielectric coefficient wet TRPEPSI l Imaginary part of dielectric coeff wet TRPREFL Visible reflectivity Radars The next file RDLIB contains the radar data beginning with three header lines for identification of variables Because of the multifunction character of the radars the number of data lines for each equipment iepends on the equipment items viz The first line always contains four - 120 - RDLTYP Radar type RDLNAME Radar name RDLNFUNC Number of functions performed by this radar RDLFUNC 4-char string giving functions performed by radar See ACLIB for conditions on string Meaningful characters are A G H I L Q T W The input for each function of each radar is on two lines The first presents radar electronic data as follows RDLERP Effective radiated power W RDLLFRQ Lower frequency limit of radar type RDLUFRQ Upper frequency limit of radar type MHz RDLGAN Antenna on-axis gain dB RDLNBW Receiver bandwidth MHz RDLSCN For L H or A search radars scan -z period sec For T radars lock-on and settling time sec RDLTMAX Maximum time radar will hold aircraft data sec RDLMAX Maximum range of radar against a 1 sqm target nmi RDLLOS Loss in RF lines dB positive value loss e g 10 means 10 dB loss RDLPW Pulse width microseconds RDLPRF Pulse repetition frequency pulses per second RDLNHB Horizontal beamwidth between half-power points degrees RDI NVB Vertical beamwidth between half-power points degrees RDLBL Back-lobe level dB RDLNSTACK Number of stacked beams Present only for A H L and W functions RDLSMTYP Type of SAM associated with radar - 119 - inclusion of repeater decoys A file modification adds to the end of the first line the variable JLGAIN the gain of the jammer if it were used as a repeater set to unity For most jammers this variable is not used and is Also a recent modification adds at the end of the data line for each band the variable JLBREL the reliability of that band 6 Terrain Parameters Next consider the new file MCLUT This contains the properties of the ground used for clutter multipath and optical reflectivity After a descriptive header the data for each terrain type are listed on its single line For the interpretation of the variables see the analysis The sequence of variables is as follows 7 TRPTYPE Index terrain type TRPCODE Terrain type description 5-character code TRPA Parameter A in terrain radar cross-section TRFB Parameter B in terrain radar cross-section TRPC Parameter C in terrain radar cross-section TRPD Parameter D in terrain radar cross-section TRPROUGH RMS roughness parameter cm TRPEPSR O Real part of dielectric coefficient dry TRPEPSI 0 Imaginary part of dielectric coeff dry TRPEPSR 1 Real part of dielectric coefficient wet TRPEPSI l Imaginary part of dielectric coeff wet TRPREFL Visible reflectivity Radars The next file RDLIB contains the radar data beginning with three header lines for identification of variables Because of the multifunction character of the radars the number of data lines for each equipment depends on the equipment items viz The first line always contains four - 121 - For L H or A radars set RDLSMTYP 0 RDLPOL Polarization H V The second line for each radar gives its susceptibility to six types of jamming technique and its vulnerability to five types of anti-radiation missiles The susceptibilities are in the order from most susceptible to least and the variable that appears is the technique Thus the line contains RDLJTECH 0 Technique to which radar is susceptible RDLJTECH 5 RDLVUL O RDLVUL 4 see JLRDTECH in JMLIB for specifics If there are fewer than 5 ARM types in ARLIB put 0 for RDLVUL for the nonexistent types In addition for the tracking function of T radars the variable RTSCVD the subclutter visibility appears at the end of the second line For each radar the several functions must be represented Thus a radar whose value of RDLFUNC is WATx will have three pairs of data lines with values corresponding to the functions W backup search A acquisition and T tracking in that order The radars are not separated by blank lines If the radar is an IR system RDCLAS Q or an optically aimed gun RDCLAS G or the function is I the line is read with the same format but the entries correspond to different variables For an illumination function the first line contains the following variables RIERP Effective radiated power W RILFRQ Lower frequency limit of radar type MHz RIUFRQ Upper frequency limit of radar type MHz RIGAN Antenna on-axis gain dB RINBW Receiver bandwidth MHz SKKSERV Locke's K parameter SKNSERV Locke's N parameter SKTYPE Seeker type 0 for pulse doppler 1 for CW - 122 - RDLLOSS Loss in connectors and cables dB in seeker receiver SKWSERV Locke's W parameter SKTHRESH Seeker threshold for monopulse system SKNHB Seeker horizontal beamwidth deg SKNVB Seeker vertical beamwidth deg SKBL Seeker backlobe level dB RDLSMTYP SAM type placeholder RDLPOL Polarization H V The second line for illuminators is also modified The jamming techniques occupy the first six places as before but the five vulnerability values are replaced by the variables SKDELTAF Doppler bank filter width Hz SKATTNMX Maximum attenuation of doppler filter dB SKDFILTW MTI filter width Hz SKROLOFF Rate of attenuation drop-off in filter bank SKCLLEN Length of clutter element nmi IR seekers and optically aimed guns use the same input format as radars and as each other but the variables have still other meanings For an IR seeker the first line contains the variables SKIRTYP Short or long wavelength band SKFOV IR seeker field of view deg SKXNEI IR noise equivalent input watts SKLRATL Minimum S N for seeker motion dB SKURATL S N required for maximum seeker motion dB RDLSCN Scan period sec RDLTMAX Maximum time target held by jammed radar sec SKTHRESH Seeker threshhold for IR system SKRATLMX Maximum rate of seeker motion deg sec SKFLRJCTPROB Probability of rejecting a flare 123 - SKFLRJCTTIME Time for decision to reject flare sec SKTDWELL Time optical system dwells on target sec SKFOVO Optical field of view deg RDLSMTYP SAM type The second line for IR seekers uses only four variables of the 11 available the others being merely format placeholders The relevant variables are in the positions of the first technique value and the first three vulnerability values and are as follows SKAUTON Flag 1 if autonomous SKMAGNIFY Magnification of optical system RDSECTW-IDTH 1 Half-width of cued sector coverage deg SKAIMERR RMS aiming error for guns deg For an optically aimed gun the only meaningful variables are the last three on line 1 and the four on line 2 8 All others are placeholders Surface-to-Air Missiles The next file SMLIB is the most complicated since the surface- to-air missiles require the most input data The file begins with eight header lines to identify the many SAM variables Then for each SAM there is a descriptive line to identify the SAM followed by six to eight data lines the number depending on the data assembled on the effectivness of various jammers against that SAM The input for the first line is SLTYP Number identifying SAM type SLGUICL Guidance class SLNSUSC O A Artillery unguided C Command I Infrared S Semiactive Number of jammers with effectiveness data against - SLNSUSC 1 124 - this SAM type Data averaged over all ranges for argument 0 data with a signal noise threshold for argument 1 SLNRT Number of SAMs available at the launcher SLNSTO Number of SAMs in storage at the launcher SLSYSREL Overall reliability of the SAM system SLMOBLTY Probability the SAM is at a mobile site SLLREL Launch reliability SLWREL Weapon reliability SLKRMIN Miss distance inside which kill probability weapons reliability ft SLKRMAX Miss distance outside which kill probability ft SLCEP Random error in guidance system ft For guns the error is angular dispersion deg SLTRCT O SLTRCT 1 Reaction time of SAM system for first firing at target sec Values are upper and lower limits of distribution SLTREF O SLTREF 1 Reaction time of SAM system on subsequent firings sec Values are upper and lower limits of distribution SLTRLD Reloading time of SAM launcher sec The second line contains the variables SLUMIN Minimum operating altitude ft SLHMAX Maximum operating altitude ft SLRMIN Minimum operating range nmi SLRMAX Maximum operating range nmi SLTBECO Time of booster cutoff sec SLRBECO Range of SAM at booster cutoff nmi SLTINTER Duration of interstage interval sec SLTSECO Time of sustainer cutoff sec SLRSECO Range of SAM at sustainer cutoff nmi This 0 - 125 may require calculation by the user most simply by approximating the sustainer trajectory by a straight line at constant velocity SLTMAX Maximum operating time of SAM sec SLTIMCON Time constant approximating SAM dynamics sec SLGUIGAN Gain of the guidance loop SLGEELIM Maximum transverse acceleration g's The third contains propulsion data and uses metric units SLLOFT Initial loft angle of SAM degrees SLAREF Reference area for SAM m2 SLTHRUST O Thrust of booster stage Newtons SLMASSO O Initial mass of SAM kg SLMASSRT O Rate of mass loss booster stage kg sec SLTHRUST 2 Thrust of sustainer stage Newtons SLMASSO 2 Initial mass of sustainer stage kg SLMASSRT 2 Rate of mass loss of sustainer stage kg sec SLMASSO 3 Initial mass of final or coasting stage kg The next three lines of SMLIB pertain to the drag coefficient details see the analysis section under UPDSM For Line 4 contains the transition values SLMACHT K L where K is the stage L the index and SLMACHT is the Mach number at which transition take place Line 5 contains the numerator drag coefficient SLCD1 K L line 6 the denominator coefficient SLCD2 where we repeat the drag coefficient equation CD SLCDI K L l SLCD2 K L Mach No Thus line 4 reads SLMACHT 0 0 SLMACHT 0 1 SLMACHT 0 2 SLMACHT 2 O SLMACHT 2 1 SLMACHT 2 2 SLMACHT 3 O SLMACHT 3 1 SLMACHT 3 2 - 126 - and lines 5 and 6 contain the corresponding coefficients in the same order The next line contains the jamming effectiveness data averaged over all field test engagements For each jammer there is a pair of numbers-- the first the jammer type SLJAMTYP the second the factor of reduction in kill probability SLJAMSUSC For the following and last line for this SAM type for each jammer type there is a tripleL of values the first two as in the preceding line the third the critical signal noise ratio SLJSCRIT required to achieve that effectiveness The number of pairs or triplets in these lines is the appropriate value of SLNSUSC from the first data line If there are no data SLNSUSC 0 the corresponding line will be absent from the library 9 Warning Receivers The last library file WRLIB contains the data on warning receivers For each receiver type there is a descriptive header line listing the variables and the receiver name Then the first data line contains WLTYP Number identifying receiver type WLNBAND Number of frequency bands in receiver There follow WLNBAND lines giving the electronic properties per band WLNBAND cannot exceed 20 For each band the line includes WLBNUM Number identifying band WLBCODE 3-character code describing band e g MID WLBLFRQ Lower frequency limit of band MHz WLBUFRQ Upper frequency limit of band MHz WLBGAN Gain of receiver antenna dB WLBSENS Sensitivity of receiver decibels below 1 milliwatt dBm After these NWLBAND lines is a single line with the parameters of the ftrosette antenna - 127 - WLNLEAF Number of leaves in rosette WLBS Angle from nose of center of first leaf deg WLDIP Angle of elevation of antenna system from horizontal positive upward deg Horizontal beamwidth between half-power points WLNHB deg Vertical beamwidth between half-powers deg WLNVB Except for the calculation of the parameters of the drag coefficient of the SAMs the preparation of these library files only requires collection of data RJARS can be run even if there is only one equipment in each file PREPARATION OF SIMULATION FILES The preparation of the simulation files will usually require detailed investigation These files are 1 TERRA Terrain heights 2 ACVIS Aircraft visibility over terrain input 3 ACSGT Aircraft visibility over terrain output 4 RIDGE Radar-terrain ridge file input 5 RDRDG Radar-terrain ridge file output 6 BLUMX Flight path - fixed wing aircraft 7 CHAMP Flight path - helicopters 8 SCENA Simulation run parameters 9 DISPL Graphics output file The file TERRA contains the detailed terrain data giving for each terrain point the coordinates rectangular or global and the altitude in feet above sea level ACVIS displays the intervals of visibility from each radar to each aircraft It may be prepared from maps or by running the simulator in mode VIS 2 see below Mode VIS 2 creates the file ACSGT from the aircraft flight paths radar positions and terrain file TERRA ACVIS may then be transcribed from ACSGT - 128 - Similarly RIDGE presents the ridge data as a function of azimuth from each radar It may be prepared by the RJARS simulator by running the mode VIS 4 which will produce the output file RDRDG be transcribed from RDRDG RIDGE may then At RAND both ACVIS and RIDGE are usually prepared by CAGIS which is considerably more efficient than RJARS at this type of calculation The files BLUMX and CHAMP contain the flight path data They are prepared at RAND by using the appropriate flight path simulator Blue Max or Champ An outside user who does not have Blue Max or Champ can use his or her own simulator provided the output format matches the description below The file DISPL is an output file that contains the data necessary for RAND's graphics program It is in the format employed by CAGIS and as mentioned this part of RJARS is the only part not fully portable The scenario file SCENA contains the information required for each simulation run It includes number of elements aircraft radars etc a set of flags describing the simulation conditions choices for general parameters such as time step printing options the details on aircraft types flight paths and maneuvers radar types positions and reporting site and command site locations and reporting and communications delays 1 Terrain Data The file TERRA has been described in the subsection UPDTR of the analysis section After a single header line the following items appear on a single line TRLGMIN Minimum terrain longitude TRLGMAX Maximum terrain longitude TRLTMIN Minimum terrain latitude TRLTMAX Maximum terrain latitude - 129 - TRDX Longitude element length TRDY Latitude element length After another header each line of TERRA contains the latitude longitude height above sea level and type of two terrain elements in the order TRLAT 1 TRLONG 1 TRALT 1 TRTYP l TRLAT 2 TRLONG 2 TRALT 2 TRTYP 2 Entries in TERRA can be either in RJARS rectangular coordinates or in global coordinates degrees and fractions of degrees not degrees minutes and seconds but then the matching coordinates must be used when running the simulation The available terrain types are described in the discussion of MCLUT The terrain field must be organized such that the number of elements along each latitude or longitude line is odd to any size Elements may be entered in any order It may be scaled After all have been entered the total number being odd an additional element should be used as a terminator This terminator should have its latitude and longitude outside the terrain field and an altitude greater than 30 000 feet thereby corresponding to no point on Earth RJARS will recognize this fictitious element as the end of the file 2 Aircraft Radar Intervisibility Data The mode of operation of terrain simulation is controlled by the parameter VIS which is an input from the scenario file SCENA If the terrain modes VIS 0 or VIS 3 are to be run it does not matter what is in the files ACVIS and ACSGT the file ACSGT If VIS 2 is run it will generate The items appearing on a line are as follows NTAB Line number TON Time aircraft becomes visible to radar - 130 - TOFF Time aircraft ceases being visible to radar IAC Number identifying aircraft IRD Number identifying radar In the file ACSGT the items appear in the order of increasing values of TON If several aircraft become visible to several radars at the same time RJARS will sequence them by aircraft number and then by radar number The end of the file is marked by the terminator line 1000 9999 0 1 1 The first element may be any number larger than the last number used to count data lines The important item is the 9999 which ensures that RJARS will not attempt to read past the end of the file during the simulation After VIS 2 has been run the file ACSGT should be copied to another name for preservation since ACSGT is destroyed each time RJARS is run As mentioned at RAND ACVIS is usually prepared by CAGIS which organizes the radars flies the aircraft and produces the output file in the indicated format 3 Ridge Data The associated files RDRDG and RIDGE contain the ridge data The data are used for clutter calculations to determine if the ground is visible at relevant points and for optical equipments to ascertain if the background is sky or ground RJARS prepares the ridge data by running it with VIS 4 which produces the file RDRDG Like ACSGT RDRDG is destroyed each time RJARS is run so it should be transcribed immediately After a header line RDRDG contains a list of radars with each line containing the radar identification latitude and longitude These are in the appropriate coordinate system rectangular or global After the listing and another header comes the main part of the ridge file arranged so all the data for a given radar are in sequence each data line there are five items as follows On - 131 - RDIDEN'T Radar idcntification AZIMUTH The angle for which ridges are being calculated deg RDRIDGDPR Depression angle of the line of sight to the present or previous ridge deg RDRIDGDIST Distance to the ridge or ground intercept point nmi TYPE Integer setLing if we are seeing an entry into ground visibility 0 or a masking 1 For each radar an each direction the first item represents the point under the radar for thich the depression angle is 90 degrees the distance is 0 nmi and the type is 0 indicating the ground is visible The next line will be the first point where the ground becomes masked with the depression ang the type 1 to that point the range to that point and If the ground rises enough beyond this point that it again becomes visible to the radar the depression angle is that of the first ridge the range is to the new point and the type is 0 This sequence is continued out to the terrain border in the given direction If the ground is visible at that location an artificial ridge is created so RJARS radars will not see outside the terrain limits number of ridges in a given direction is arbitrary Clearly the Just like ACVIS at RAND RIDGE is usually prepared by CAGIS The number of directions in which ridges are calculaLed is controlled by the parameter nrdgangle which is located in a #define statement at the beginning of the assemblage of varidble declarations rjarsdecls h it is defaulted to 37 in both RJARS and CAGIS corresponding to a 10 degree spacing betueen ridges If the user wishes to change the ridge spacing it is necessary to change nidgangle and then recompile RJARS 4 Scenario The scenario file SCENA contains the information required for the execution of a simulation It must be prepared for each run although sometimes only a few changes need be made to modify SCENA for new conditions variables After a header the first line of SCENA contains the - 132 - NAC Number of aircraft NRD Number of radars includes long-range search height-finders acquisition radars trackers multifunction radars IR systems and optically aimed guns NSI Number of sites NSC Number of command sites NREP Number of Monte Carlo repetitions VIS Over-terrain visibility mode NDOF 0 No terrain 1 Visibility from ACVIS file 2 Preparation of visibility file 3 Terrain included directly 4 Preparation of ridges Number of degrees of freedom for aircraft rcs 3 Radar cross section data in azimuth plane only 5 Radar cross section data in both azimuth and elevation planes After another header line to indicate the variables that follow the next line of SCENA includes the following set of simulation flags Unless otherwise stated for each flag 1 Yes 0 No IAVAIL Recalculation of radar availability 1 Availability recalculated at each iteration 0 Availability calculated only at beginning of simulation ICLUT Clutter calculations included IMULT Multipath calculations included IWET Wet terrain properties ISNOW Terrain covered with snow IJANUS JANUS probability calculations at end of simulation INSFD Permanent radar numbers from threat laydown - 133 - included in radar input data INIGHT Night operations ILOBS Special calculations for low-observable aircraft IR and optical systems disabled in effect Following another header are four more flags pertaining to optical systems IOPT Optically aimed weapons employed ISUMMER Contrast transmission for season ISEEING 1 Summer conditions 0 Winter conditions Contrast transmission conditions 1 Median seeing 0 Seeing quality exceeded only 10 percent of the time ISUN Sun visible in sky After another header is a set of general simulation variables DT Time step sec TFIN Termination time of scenario sec DTG Guidance time step sec TDAY Time of day hr SEED Integer to start the random number generator Another header then a set of character variables SIZE Character to indicate number of change points in aircraft flight maneuvers Use S if the number of change points is 10 or fewer M if 11-25 L if greater than 25 SRBMOD Character for tracker servo mode F fixed servo bandwidth A adaptive servo bandwidth PRNTMOD Character for radar printout S shortened format anything else full descriptive - 134 - format SMPRNT Character for SAM printout Y prints details of flight under control of IPG N prints details only when range to target 1000 ft HF CiLaracter for height-finders N height finders not included NOSHT Character for SAM operation Y SAMs never shoot RCTDISTRIB Character for the type of distribution for the SAM reaction and refire times U uniform N normal Another header then printing controls and miscellaneous parameters IP Control Search radar printout occurs each IP'th time step IPA Control Aircraft position printout occurs each IPA'th time stop IPG Control SAM detailed data printout occurs each IPG'th subdivided time step COORD PRBTYP Input-output coordinate choice 1 Input and output rectangular 2 Input and output global 3 Input rectangular output global 4 Input global output rectangular Probability choice or jamming table 0 Sinusoidal curve fit 1 Cookie cutter 2 Jamming effectiveness tables averaged over jamming conditions 3 Jamming effectiveness tables signal noise ratio as parameter - 135 - The next two lines of SCENA are present only if COORD 1 so either input or output is global first a header then on one line DLATO Degrees for reference latitude MLATO Minutes for reference latitude SLATO Seconds for reference latitude HLATO Hemisphere for reference latitude N S then another header then on one line DLONGO Degrees for reference longitude NLONGO Minutes for reference longitude SLONGO Seconds for reference longitude HLONGO Hemisphere for reference longitde E W Following another header are the parameters for the field of action of the simulation in rectangular coordinates LATMIN Minimum ordinate nmi LATMAX Maximum ordinate nmi LONGMIN Minimum abscissa nmi LONGMAX Maximum abscissa nmi After another header SCENA presents the initial parameters for each aircraft If COORD 2 or COORD 4 then on each line are the variables ACIDENT Identification number of aircraft ACTYP Number identifying aircraft type ACGROUP Group with which the aircraft is initially associated ACDLAT Degrees of initial latitude ACMLAT Minutes of initial latitude ACSLAT Seconds of initial latitude - 136 - ACHLAT Hemisphere of initial latitude N S ACDLONG Degrees of initial longitude ACMLONG Minutes of initial longitude ACSLONG Seconds of initial longitude ACHLONG Hemisphere of initial longitude E W ACZALT Initial altitude above terrain ft ACHDG Initial heading degrees clockwise from north ACVEL Initial velocity knots ACJMTYP Type of jammer on board the aircraft ACWRTYP Type of warning receiver on board the aircraft ACRDJM 4-character code--types of radars the aircraft should jam L H A T or I represent possible choices 0 fills out the code to four characters ARMN Number of ARMs on board ACPAINTL Color of lower surface ACPAINTU Color of upper surface If COORD I or COORD 3 the variables ACDLAT ACHLONG are absent and the variables ACLAT Initial ordinate nmi ACLONG Initial abscissa nmi appear between ACGROUP and ACALT If ARMN 0 the next line of SCENA contains the input data for all the ARMS in that aircraft viz ARMTYP J 0 Type of first ARM on aircraft J ARMBD J 0 Frequency band of first ARM on aircraft ARMRD J 0 Target radar of first ARM on aircraft J If the ARM is preprogrammed there will be a radar number here If the ARM is opportunistic the value 0 will appear ARMTYP J 1 Type of second ARM on aircraft J etc - 137 - The aircraft data and ARM data if present are listed for all NAC aircraft in the simulation After the next header the flight man uvers for the number of aircraft NAC and the communications connecting and cutting for the fictitious NAC lst aircraft are listed Beginning with aircraft number 1 the maneuvers for each aircraft are listed in nondecreasing time sequence in the form TIME Time when maneuver occurs CHANGE 5-character code identifying maneuver type For details see the analysis section X First parameter for maneuver Y Second parameter for maneuver The last maneuver for each aircraft and for the communications system must have TIME 9999 After another header comes the radar parameters If COORD 1 or COORD 3 these are RDIDENT Identification number of radar RDMSFDNO If called by IMSFD see above number of radar in threat laydown This number must be followed by a space before the comma RDLAT Radar ordinate nmi RDLONG Radar abscissa nmi RDZALT Radar height above terrain ft Includes antenna height If COORD RDTYP 4-character code identifying radar type RDATSITE Site to which radar reports RDSECTMEAN Center line of radar sector of coverage deg RDSECTVIDTH Half-width of sector of coverage deg 2 or COORD 4 the ordinate and abscissa are replaced by degrees minutes seconds hemisphere as with aircraft All NRD radars - must be listed 138 - They may be in any order IR and optical systems are subsumed under the category radar After another header comes the single item DLYMULT This is a factor that multiplies all the communications and decision delays in the system It would normally be defaulted to 1 Following another header is the site data For all NSI sites the parameters on the site line if COORD 1 or 3 are SIIDENT Site identification number SILAT Site latitude nmi SILONG Site longitude nmi SIZALT Site height above terrain ft SIUPDLY Communications delay site to command site sec SIDNDLY Communications delay command site to site sec SIRPT Command site to which the site reports SIMOEILE Flag 1 - Site is mobile and subject to availability restrictions 0 - Immobile available If COORD 2 or 4 the latitude and longitude in rectangular coordinates are replaced by their values in degrees minutes seconds and hemisphere Finally after still another header SCENA is completed with the command site data For each of NSC command sites with COORD 1 or 3 CSIDENT Command site identification number CSLAT Command site latitude nmi CSLONG Command site longitude nmi CSZALT Command site height above terrain ft CSDECDLY Command site decision delay sec For COORD 2 or 4 see above files This concludes the description of the input 139 - - OUTPUTS RJARS provides outputs at each time step summaries at the end of each run and a graphics output file When several Monte Carlo runs are executed the detailed outputs position tracking error etc are printed only during the first run Thereafter only events detections SAM launches etc 1 and the summaries are printed Printed Outputs Aircraft outputs appear each IPA'th time step and may be in rectangular or global coordinates Specific items printed are latitude longitude altitude heading velocity and the number of ARMs antiradiation missiles remaining on that aircraft If an aircraft is maneuvering the maneuver state e g current heading is printed every time step during the maneuver Search nd acquisition radar outputs printed each IP'th time step provided the target has been in the radar main beam during that time step are time of detection identification signal signal-to-noise ratio range bearing probability of detection and position measurement errors Trackers display the same information except that the time is replaced by the word TRACK the probability of detection by the elevation and the errors may include the word NO if the lock in azimuth or elevation is broken by jamming step for which they are turned on Trackers print at every time If clutter is being calculated the amplitude of the clutter signal is printed after the true signal value If multipath is included the multipath factor modification of the true signal is printed For optical systems indicated by the word OPTICS in the print the contrast at the viewer and the cycles across the target divided by the threshold detectibility are printed plus a detection probability and random draw for the detection or recognition phase of operation IR seekers have the same printout as trackers marked by the word IRSEEK and not including the tracking errors ARMs in flight print at each time step their latitude longitude altitude target identification and the range to the target self-destruct it is announced If they If and when an ARM reaches its target the kill probability and outcome are presented - 140 - SAMs in flight print under the control of the parameters SMPRNT and IPG Normally SMPRNT is set to N to avoid excessive output in which case at each time step for which the SAM is more than 1000 feet from its target it will print identifications the SAM state boosting sustaining coasting and the ranges from the SAM to its launcher and its target If SMPRNT Y or if the SAM is less than 1000 feet from its target it will print at each IPG'th subdivided time step within the full time step the following variables SAM SAM identification TGT Target identification TIME Current time sec FLTIME Flight time since launch sec STATE Current state B I S or C ACLAT Aircraft latitude including measurement errors nmi ACLONG Aircraft longitude as above nmi ACALT Aircraft altitude as above ft LAT SAM latitude LONG SAM longitude nmi ALT SAM altitude ft RANGE SAM range from tracker nmi ELEV SAM elevation angle from tracker deg AZ SAM azimuth angle from tracker nmi deg clockwise from North VEL SAM velocity fps PITCH Elevation angle of SAM velocity deg HDG Heading angle of SAM velocity deg clockwise from North RNGTN Range from SAM to target nmi ELEVIM Elevation angle from SAM to target deg AZTM Azimuth angle from SAM to target deg These quantities are printed on three lines with the words displayed as listed If the SAM uses a semiactive seeker the following quantities 141 - - are printed on an additional line SEEKAZ Azimuth toward which the seeker is pointing deg SEEKEL Elevation toward which the seeker is pointing deg AZCOM Commanded change in azimuth direction deg ELCOM Commanded change in elevation direction deg AZSK Azimuth displacement from boresight deg ELSK Elevation direction from boresight Aircraft may defend themselves against IR systems by launching flares At the time of launch of an IR SAM a random draw determines if the aircraft detects the launch The event and result are printed If the detection was successful the aircraft may launch a succession of flares for which the launch event and success are printed may or may not identify and reject each flare The seeker At each IPG'th subdivided time step while the SAM and flares are in flight the angles of the seeker to the target and to each flare are printed displaying how it may transfer allegiance as time progresses destruction events are printed Flare burnout and SAM countdown and launch events are printed at their time of occurrence When the SAM reaches its target the times of closest approach range from the launcher miss distance kill probability value of the random draw variable and outcome are displayed The summary printouts are described fully in the analysis section under the subroutine OUTPUT and the user should refer to that material 2 Graphical Outputs The RJARS graphics output is incorporated in the file DISPL As has been stated many times DISPL is in CAGIS format and cannot be used or read unless CAGIS is available In addition the preparation of DISPL uses the CAGIS subroutine mg-put and if RJARS is to be used at a facility which does not have CAGIS all appearances of this subroutine must be deleted The DISPL file contains the following information marked by the parameter dtag which tells CAGIS what parameters are being transmitted - dtag 1 142 - Radar parameters IDENT LAT LONG ZALT TYPE SITE COMMAND SITE MINIMUM SECTOR COVERAGE ANGLE MAXIMUM SECTOR COVERAGE ANGLE dtag 2 Flight path parameters IDENT TIME LAT LONG ZALT ALT VEL HDG dtag 3 Flight path extension or RJARS aircraft path parameters as in dtag 2 dtag 4 Site or command site parameters IDENT LAT LONG ZALT ALT SIRPT for sites -1 for command sites dtag 5 Initial values NAC NRD NSI NSC TRLTMAX TRLTMIN TRLGMAX TRLGMIN dtag 6 Probability data for JANUS ACIDENT RDIDENT 0 for killing before or after LOSl LOSN INTERVAL NUMBER START OF INTERVAL END OF INTERVAL KILL PROBABILITY DENSITY dtag 7 Maneuver profile ACIDENT PROFTIME PROFCHANGE PROFX PROFY The foregoing parameters are sent to DISPL only once end of simulation for dtag 6 as developed for dtag 3 beginning of simulation for all others In addition information is sent on each iteration marked by the following values of dtag dtag 10 JREP 1 Search and acquisition radar summary parameters RDIDENT ACIDENT CODE for event type EVENT TIME Code 1 for entry 2 for detection 3 for loss of detection 4 for exit dtag 10 JREP 2 Track radar summary parameters RDIDENT ACIDENT TIME ACQUISITION ON TIME ACQUISITION OFF TIME TRACKING ON TIME TRACKING OFF dtag 10 JREP 3 SAM summary parameters IDENT TARGET SAM NUMBER FROM LAUNCHER LAUNCH TIME INTERCEPT TIME CODE for intercept result 0 launch failure - 143 - 1 still in flight 2 lost track 3 crashed 4 missed target 5 shot target down dtag 10 JREP 4 Anti-radiation missile summary parameters AIRCRAFT carrying ARM IDENT NUMBER of ARM launched from that aircraft TARGET RADAR LAUNCH TIME ARRIVAL TIME 9999 if destructed in flight CODE for result 0 lost track I missed target 2 killed target 3 still in flight dtag 10 JREP 5 SAM flight parameters LAUNCHER IDENT TARGET IDENT NUMBER from that launcher CURRENT subdivided TIME LATITUDE LONGITUDE ALTITUDE above sea level dtag 10 JREP 6 Radar or optical scan limits RDIDENT TIME SCAN LOWER LIMIT SCAN UPPER LIMIT Printed only upon changes dtag 10 JREP 7 Jammer on and off times ACIDENT RDIDENT TIME CODE for event 0 on 1 off The RJARS graphics program developed by Gail Halverson can produce a variety of displays Usually the terrain is displayed first then the defensive laydown indicated by a set of icons at the appropriate positions The aircraft paths are shown and their condition with respect to the defense indicated by changing color Thus an undetected aircraft path is black one that has been detected by search radars is gray When radars are attempting to acquire the path is blue when they have acquired and a tracker is on it becomes yellow If a SAM is in flight against that aircraft the path turns orange The path of a SAM is in red Intercepts are marked by small stars for misses large stars for kills path does not continue may be stepped If an aircraft is killed its Paths may be laid down all at once or the time Changes in radar scan coverage or jammed condition are shown by changing marks on the radar icon may be shown in sequence alongside the main display The successive iterations The summary results are presented as a legend - 144 - RJARS may be compiled with the standard UNIX C Gcmpiler Except for the frequently mentioned display limitations there should be no problems with program portability To compile RJARS on another installation remove all appearances of the command mg-put from the program RJARS will abort if there are data read-in errors and indicate which type of equipment aircraft radar etc is at fault These errors can usually be found quickly by scanning the appropriate section of SCENA Frequent causes of such errors are typing a period instead of a comma as a separator between data entries or failure to use the proper type of quotation marks on character entries There appeared at this point in the earlier version of this report a set of sample input files and typical output These were provided ds accompaniments to the code so the reader could test with files known to be correct Since the code is no longer included in the report these sample files and typical outputs have been dropped - 145 - PROGRAMMER'S GUIDE V RJARS is a completely sequential program It contains no goto statements but tests flags or variables and either performs or doesn't perform the indicated program sequences Nesting levels may be very deep level 13 is ruached in UPDRS but no loop is exited with a branch command so the sequelce should be easy to follow by simply counting DO ana END statements in the PL-I version or and in the C version The only anusual program device in the PL-I version of RJARS is used during the reading of the liorary files and is caused by the oneway nature of the PL-T input stream To illustrate how it operates consider the input of the warning receiver data Before these data are read the type of receiver on each aircraft has been read from SCENA A parameter K is set equal to the number of aircraft and the command DO while K $ 0 is given The data on the first type of warning receiver in the library are read from WRLIB through The sequence of aircraft is -un For tach aircraft whose designated warning receiver is of the first type the parameters of the receiver on that aircraft are set equal to the library parameters and K is decremented After all aircraft have been checkcd data on the second receiver are read and the process repeated The operation will terminate either whe K 0 all aircraft receivers properly loaded or an end-of-file condition is reached In the former case the program continues in the latter the flag EOFFLG is set to 4 device All the library files are read using this If EOFFLG has any value other than zero at the end of the data read-in RJARL aborts and prints the proper error message RJARS has been translated into the C computing language to operate on UNIX installations between the programs There are only a few significant differences The separation of the radars into two lists which was implemented in the PL-I version to save space was not included in the C version since our installation had plenty of computing space available from PL-I The arraying structure in C is different First in C the first element in an array is designated with 146 - - the index value 0 whereas in PL-I the index is 1 Consequently the arrays had to be carefully tracked and frequently 1 had to be subtracted from an input index value to be certain that array elements are stored in the proper location Second array structures in C require full qualification of their variables which leads to such equivalences as ARMALT J L - ANTIRADIATIONMISSILE J ARM L ALT where the first expression on the right denotes an outer structure ARM is an inner structure and ALT is the variable Because of this requirement the C program has longer statements for the same content The terrain indexing is different in the C program Since matrices in C must begin at 0 and the terrain matrix for PL-I has been centered at 0 0 the parameters ntr ntr2 have been added to the externally defined matrix sizes that are required in the C program Here ntr is the full size of the terrain matrix and ntr2 is half that The terrain elements are centered on the point ntr2 ntr2 and the index finder subroutine TRINDEX has been adjusted to reflect this There are command and notation differences between PL-I and C such as PUT EDIT in PL-I is replaced by printf in C attended to in the translation These have all been The equations which have been programmed are identical so aside from the indicated differences the programs are quite equivalent The C language includes a rewind command for files so the special read device described above for PL-1 is not necessary Indeed certain of the files are rewound of necessity such as the rewind of ACVIS for Monte Carlo sequencing Also some files are read twice during data input to first establish the amount of space that must be allocated and then read in the data The major programming difference between the present version of RJARS and the C program at the time the previous report was written is the use of dynamic allocation The dynamic allocation procedures were developed by Jim Gillogly and then extended by the author The problem - 147 - with the earlier version was that all arrays had their dimensions set by numbers defined at compile time Thus if the user ever desired to treat a scenario with 500 radars it would be necessary to provide space for 500 radars for all scenaria This was an extremely wasteful process The cure was to define all arrays that might have variable dimension by pointers AIRCRAFT For example the aircraft array is defined as The number of aircraft NAC is read from the scenario Then the following command if AIRCRAFT struct acstruct calloc NAC sizeof struct acstruct NULL outofmem AIRCRAFT allocates space for NAC aircraft each having all the variables defined in the structure acstruct If there is insufficient space available the subroutine outofmem will indicate that the space overflow occurred during the allocation to the array AIRCRAFT used for all such arrays Similar declarations are Those declarations that involve only the dimensions NAC NRD NSI NSC NCP or NGUI--respectively the number of aircraft radars sites command sites change points or guidance time steps--are collected in the subroutine allocate Others such as those that depend on the number of ridges in a given direction from a radar are allocated after the necessary information to scale them has been read or calculated The space savings produced by this dynamic allocation can be very great Thus suppose the user with 500 radars discovers that only 20 of them are involved in the actual simulation and that the rest are present but never doing anything The 20 active radars can be abstracted from the set and excursions from the base case can be run using only about 4 percent of the space previously used In contrast with the older version of RJARS all 500 radars would have to be kept for Lhe excursions - 148 - Another important change is the addition of a graphics program This is directly associated with the CAGIS system and is the only The graphics program was portion of RJARS that is not portable developed by Gail Halverson Much of it is resident in CAGIS The only graphics function in RJARS is the writing of a file DISPL that contains the data which will be presented in the graphics The transmitted information uses the integer dtag to identify which graphics data are being sent the integer dtype to show its nature only dtype 7 corresponding to floating point numbers is used and dnitems to show how many items are on a data line The array dbuf containing 20 elements carries the actual numbers If a variable which is to be sent to DISPL is not a floating point number it must be cast as one The command mg-put dtag dtype dnitems dbuf calls a CAGIS routine to convert the items to a compressed format and store them for later use by the CAGIS graphics procedures Among the information items sent to DISPL are the following 1 Numbers of aircraft radars sites command sites and terrain limits 2 Radar identification type location and site 3 Site identification and command 4 Command site location 5 Flight path identification with position and velocity 6 Aircraft continuation of flight path position and velocity 7 Scan limits for sector scanning systems 8 Flight paths of SAMs 9 Times when aircraft enters is detected or leaves search radar field 10 Times of assignment acquisition on and off and tracking on and off for a track radar 11 Results of SAM endgames 12 Results of ARM endgames - 149 - The difference between flight path and flight path continuation is that if the aircraft flight path has been derived from a flight path generator then it may also involve straight and level flight extensions at the beginning and end of the path These may vary from iteration to iteration depending on how long the aircraft survives The longest continuation is used for the graphics Certain of these items such as the radar locations are fixed throughout the simulation and need be transmitted only once Others such as the results of SAM endgames may differ and have to be sent every iteration The iteration dependent information is marked by the tag which at each iteration is incremented by 10 for the appropriate variables GLOSSARY RJARS involves so many variables that a glossary is mandatory Most of the variables are themselves arrays and are included in structures The dimensions of the arrays a description of the variables and their units should be given To avoid much writing we use the convention that the first argument of the array is subsumed in the variable name Thus the first variable in the list ACACCL belongs to the structure AIRCRAFT as indicated by the initial letters AC and is a one-dimensional array of size NAC The structures size and opening letters of the variables are as indicated AIRCRAFT NAC AC ACSTATE NAC AS AN'TIRADMISSILE NAC ARM ANTIRADMISSILELIB ARL COMMANDSITE NSC CS DETECTIONS NRD NAC DT DETSUM NRD NAC 10 DTS FACET NFACET FA FLARE NFLARE FL FLIGHT-PATH NFLPATH FP - 150 - IRDATA variable IR JAM NAC JM JAMMERLIB JL PROFILE NAC l PROF RADARS NRD RD ILLUMINATIONRADAR NRD RI SEARCH-RADAR NRD RS TRACK-RADAR NRD RT RADARLIB RDL SITE NSI SI SEEKER NRD SK SIMPLESAM NRD SM SAMLIB SL TERRAIN 2 NX 3 2 NY 3 TR TERRAIN-PARAMETERS nttype TRP VISDATA NAC NRD VIS WARNING-RECEIVER NAC WR WARNINGRECEIVERLIB WL The words aircraft radar etc will be omitted from the description of the variable since they are implicit in its designation Variables not in the structures are described in full Variables that are part of multidimensional arrays will have only those dimensions beyond the first indicated For example the variable RTLATI which has the dimensions NRT NGUI is referred to in the glossary as RTLATI NGUI the first dimension NRT being implicit in the initial RT - 151 - GLOSSARY OF VARIABLES Variables with the same meaning but different references are listed together Flag status if set is shown Matrix dimensions exclude first if identified by variable name Upper and lower case letters for variables are distinguished ACACACCL ACACCLMB ACACPITCH ACACPITCH1 ACACPITCH2 ACACTURN ACALPHA1 RCSNAZ ACALPHA2 RCSNAZ RCSNEL ACALT ACALTG NGUI ACALTO ACALTP 3 ACALTPROJ ACBANK ACBANKG NGUI ACBANKO ACBLKSTRT ACC ACCEL ACCRASHT 20 ACDECNUM 10 ACDELALTPROJ ACDELLATPROJ ACDELLONGPROJ ACDESTT ACDISP ACDLAT ACDLONG ACEGLNLG ACFLAZ 2 ACFLFUSDISP ACFLTILT ACFLWINGDISP 2 ACFPPATHDLY ACFUSDIAM ACGLNAZ ACGLNEL ACGROUP Acceleration knots sec Climb rate fps Pitch acceleration deg sec2 during first part of climb maneuver during last part of climb maneuver Turning rate deg sec Radar cross-section 3 deg of freedom dB lsqm Radar cross-section 5 deg of freedom dB lsqm Altitude above sea level ft true interpolated initial present and two past values projected from SAM launch time to present Bank angle right wing down deg true interpolated initial Time of starting of blink jamming sec Acceleration entry for SRVERR Subroutine for aircraft acceleration Time of apparent aircraft crash sec Identification number for decoys Change in projected altitude in DTG latitude longitude Time of arrival at destination Displacement of towed decoy from parent ft Degrees of latitude Degrees of longitude Effective glint length ft Azimuth of each flare launcher from forward Longitudinal displacement of flare launchers from center of nose-to-tail line ft Tilt of flare launcher from vertical deg Lateral displacement of each flare launcher from center line ft Time of joining flight path sec Fuselage diameter ft Azimuth glint error Elevation glint error Group to which ac belongs - ACGROUPO ACHDG ACHDGG NGUI ACHDGO ACHDGP 3 ACHLAT ACHLONG ACIDENT ACIRSIG 2 13 13 ACJMTYP ACKILLT ACLAT ACLATG NGUI ACLATO ACLATP 3 ACLATPROJ ACLENGTH ACLFLARE ACLIB ACLONG ACLONGG NGUI ACLONGO ACLONGP 3 ACLONGPROJ ACLOSi ACLOSN ACMLAT ACMLONG ACNOSEAREA ACNOSEDET ACNPITCH ACNPITCHG NGUI ACNPITCHO ACPAINTL ACPAINTU ACPITACDN ACPITACUP ACPITCH ACPITCHG NGUI ACPITCHO ACPITCHP 3 ACPITCHC ACRCS ACRCSAZRES ACRCSELRES ACRCSNAZ ACRCSNEL ACRDJM ACRDJMCL 4 ACRDVISKEY NRD 152 - Initial group to which ac belongs Heading deg clockwise from North true interpolated initial present and two past values Hemisphere of latitude N S Hemisphere of longitude E W Aircraft identification number tail no Radiant intensity in each spectral band in steps of azimuth and elevation Type of jammer on aircraft Time when aircraft killed Latitude in rectangular coordinates deg true interpolated initial present and two past values projected from SAM launch to present time Overall length ft Number of flares per dispenser File Aircraft dimensions and parameters Longitude in rectangular coordinates deg true interpolated initial present and two past values projected from SAM launch to present time Time of first LOS to target for JANUS see Time of last LOS to target for JANUS sec Minutes of latitude Minutes of longitude Nose projected area sq ft Probability of detecting a flare nose-on Pitch angle of nose deg from horizontal true interpolated initial Color of lower surface 2-char code Color of upper surface 2-char code Maximum acceleration in downward pitch g's Maximum acceleration in upward pitch g's Pitch angle deg from horizontal true interpolated initial present and two past values Critical pitch angle deg File Radar cross-section Radar cross-section resolution in azimuth deg Radar cross-section resolution in elevation deg Number of elements in azimuth in cross-section Number of elements in elevation in cross-section General types of radars to be jammed individual Key to file visibility data - ACREFL 2 ACROTORRCS ACSENSORRCS ACSGT ACSIDEAREA ACSKIDFUSE ACSLAT ACSLONG ACSPAN ACSTATE ACTACCL ACTAILAREA ACTAILDET ACTCLMB ACTCLMBH ACTCLSTART ACTLAT ACTLONG ACTPITCH ACTPITCH1 ACTPITCH2 ACITTURN ACTURNAC ACTVISOF NRD ACTVISON NRD ACTYP ACLTYP ACVEL ACVELG NGUI ACVELO ACVELP 3 ACVELF ACVIS ACWINGAREA ACWINGCHORD ACWRTYP ACYAW ACYAWG NGUI ACYAWO ACZALT ACZALTO ACZALTP 3 AIRCRAFT AIRCRAFTLIB ALLJAM ALT ALTI ALT2 ANTIRADMISSILE ANTIRADMISSILELIB ANTPAT1 ANTPATS AREACLU7 2 ARLBDNO 153 - Reflectivity of lower and upper surfaces Radar cross section of helicopter rotor dB lsqm Radar cross section of mast-mounted sensor dB lsqm File Visibility data output file Side view projected area sq ft Height of body center above skid helos ft Seconds of latitude Seconds of longitude Wingspan ft Structure Aircraft state conditions Time for acceleration maneuver sec Tail area side view sq ft Probability of detecting a flare from tail view Time for climb maneuver sec Time for vertical climb helos sec Time of start of vertical climb sec Latitude deg Longitude deg Time for pitch maneuver sec during first part of climb maneuver during last part of climb maneuver Time to perform turn maneuver sec Maximum acceleration in turn gees Time radar ceases being visible Time radar becomes visible Type of aircraft Velocity knots true interpolated initial present and two past values Velocity fps File Provides visibility data Wing aree sq ft Chord length across wing ft Type of warning receiver on board Yaw angle deg from nose deg true interpolated initial Altitude above terrain ft initial present and two past values Structure Aircraft variables Flag Radar jammed in all directions Altitude entry for SAM propulsion Lower and upper atmospheric transitions Structure Anti-radiation missile variables Antenna pattern for pencil beams Antenna pattern for stacked beams Area of pulse doppler clutter patches Identifier for frequency band - ARLIB ARLNBD ARMALT ARMBD ARLBD ARMBDLFR ARLBDLFR ARMBDUFR ARLBDUFR ARMCL ARMHDG ARMKILLT ARMLAT ARMLNCH NRD ARMLOFT ARLLOFT ARMLONG ARMN ARMNL ARMOFF ARMPAR ARMPITCH ARMPKFACT ARMKPROB ARMRD ARMRMAX ARLRMAX ARMRMIN ARLRMIN ARMRSLT ARMSTATE ARMTDLY ARLTDLY ARMTLNCH ARMTOFF ARMTYP ARLTYP ARMVEL ARLVEL ASACCL ASADVDET ASASSNNO ASBLANK ASBLINKON ASCARRY ASCLMB ASDEAD ASENG ASFIRDET ASFLNEXT ASFLPAT ASHOMFLG ASIBLINK ASIDECOY ASIFLPATH ASIHIDE ASIHIDEO ASINBEAM NRD ASINFLD 154 - File Anti-radiation missile parameters Number of frequency bands available Altitude of ARM ft Structure Band variables Lower frequency limit of band MHz Upper frequency limit of band MHz Class of ARM - preprogrammed opportunistic Heading deg clockwise from North Time ARM reaches its target for kill Latitude nmi Flag ARM aimed at that radar Initial loft angle deg Longitude nmi Number of ARMs initially on aircraft Number of ARMs left on aircraft Subroutine Set parameters to drop ARMs Structure Individual ARMs Pitch angle deg from horizontal Reduction factor for ARM kill probability ARM kill probability Target radar Maximum range capability nmi Minimum range capability nmi Result of attack State of ARM char Time of flight without guidance Time of launch sec Time target radar goes off and ARM loses guidance Type of ARM Velocity of ARM fps Flag Aircraft accelerating Time a radar first points at an aircraft Temporary tracker assignment number Flag Aircraft blanked from radars Flag Engaged in blink jamming Carrier aircraft for cruise missile Flag Climb in progress Flag Aircraft shot down or outside terrain Number of engagements of aircraft with SAMs Flag Aircraft has been detected by somebody Next flare launcher to fire Choice - flare pattern Flag Aircraft going home Flag Capable of blink jamming Flag Aircraft is a towed decoy Index of flight path associated with aircraft Aircraft exposed O rotor exposed l hiding 2 initial Flag Aircraft scanned by radar this time step Flag Aircraft in field of action - ASIRDET NRD ASJMFLG ASKFLPATH ASKFLPATHO ASLFLARE 2 ASLFLAREO ASLOAD ASMFLARE 2 ASNCRASH ASNDECOY ASNFLARE 2 ASPARTNER ASPECT ASPTCH ASRAKFLG NRD 155 - Flag Launch from that IR site has been detected Flag Jammer on Identification no of associated flight path initial Number of flares remaining at each launcher initial Identification for cruise missile while on board carrier Total number of flares fired from each launcher Number of times aircraft has apparently crashed Number of towed decoys on aircraft Number of flares in flight from each launcher Partner for blink jamming Angle of observation from nose of ac deg Flag Aircraft pitching Flag Acquisition radar from isolated site k has been assigned command site m Flag Tracker from isolated site k is on command site m Flag Used to assign trackers Subroutine Finds possibility of assignment Number of times aircraft is scanned Flag Turn maneuver in progress Flag Aircraft helicopter in vertical climb Subroutine Atmospheric variables Attenuation of clutter in doppler filter Constant 62089911 in random number generator Flag Radar not in receiver's frequency coverage Angle between velocity and line of sight deg Backlobe level dB File Flight paths from BLUE MAX fixed-wing Velocity of light 16188 nmi microsec Atmospheric constants ASRAMFLG NRS ASRTKFLG NRT ASRTMFLG NRT ASSFLG ASSNFLG ASSN ASTOTAL ASTRN ASVCLMB ATMOS ATTN Al BANDFLG BETA BLl BLUMX C CDENS CP11 CPl2 CPl3 CP21 CP22 CP31 CP32 CTII CT21 CT31 CT32 CVS Dummy characters CH CHI CH2 File Flight paths from CHAMP helicopters CHAMP Subroutine Climb maneuvers CLIMB Power returned from pulse doppler clutter points CLPWR 2 Subroutine Clutter for pulse doppler seekers CLTSK1 Subroutine Clutter for CW seekers CLTSK2 Subroutine Clutter for search and track CLUTTER Structure Command site variables COM'MANDSITE Coordinate choice rectangular or global COORD on input or output Correlation parameter COR Number of maneuvers performed COUNT Flag Radar has scanned across axis CROSS Altitude above sea level ft CSALT Flag Broadcasting alert on that aircraft CSCOMALERT NAC - 156 - CSDEAD CSDECDLY CSDLAT CSDLONG CSHLAT CSHLONG CSIDENT CSLAT CSLONG CSMLAT CSMLONG CSPSMALT NAC CSPSMFLG NAC CSPSMLAT NAC CSPSMLONG NAC CSSLAT CSSLONG CSTLAT CSTLONG CSZALT dbuf 20 dnitems dstring 133 dtag dtype DENS DESTFLG DETECTIONS DETSUM DIFAZ DIFEL DIFFSIG 2 DIFLONG DISPL DLAT DLATO DLONG DLONGO DLYMULT DR DROPACQ DROPTCK DT DTBRG DTEL DTFLG DTG DTNEW DTPSS DTPSSL DTRNG Flag Command site not operating Decision delay at command site sec Degrees of latitude Degrees of longitude Hemisphere of latitude N S Hemisphere of longitude E W Identification number of command site Latitude of command site nmi Longitude of command site nmi Minutes of latitude Minutes of longitude Best data on ac altitude at command site Flag Data to pass Best data on ac latitude at command site longitude Seconds of latitude Seconds of longitude Command site latitude deg Command site longitude deg Altitude above terrain ft Buffer for graphics data Number of items in dbuf Buffer string for storage Identification for graphics variables Variable type for graphics float 7 Atmospheric density kg cu m Flag SAM should destruct Structure Detection variables Structure Detection summary variables Clutter in azimuth difference channel Clutter in elevation diference channel Difference signals for monopulse receiver Longitude from reference File Graphics output Degrees of latitude initial Degrees of longitude initial Multiplier for up down and decision delays Degrees to radians PI 180 Subroutine Drops acquisition Subroutine Drops track Time step sec Bearing of target for communication Elevation of target for communication Flag Aircraft detected Subdivided time step sec Flag Aircraft detected as new target Flag Aircraft detected on this scan Flag Aircraft detected on last scan Range of target for communication nmi - DTSISD DTSRDET DTSRLOS DTSTDET DTSTLOS DX DX1 DXY DXY1 DY DY1 DZ DZ1 ENDFLG EOFFLG EPS ERR EXTINCT 2 2 FACE FACET nfacet FAAZF FAELF FAITXF FAITYF FALF FARHOD FARHOM 2 FASIGF FATHETA FATYPEF FAXF FAYF FAZF FLARE FLALT FLALTVEL FLAZ FLBRITE FLELEV FLELTIME FLKFLARE FLLAT FLLATVEL FLLNCHD FLLNCHTIME FLLONG FLLONGVEL FLRNG FLSNR FLTGT FLVEL FLZALT FLPATH FLYFLARE 157 - Number of detection during this viewing Range at which aircraft detected nmi Range at which aircraft lost from detection nmi Time at which aircraft detected sec Time at which aircraft lost to detection sec Aircraft to radar abscissa nmi Aircraft to radar ground range nmi Aircraft to radar ordinate nmi Aircraft to radar altitude ft Flag Endgame in progress Flag End of a file has been reached Small constant 00001 Error in servo Extinction coefficient for optical Subroutine Contributing facets for clutter Structure Terrain facets for clutter Azimuth from radar to facet deg Elevation from radar to facet deg Longitude terrain index of facet Latitude terrain index of facet Length of line of sight within facet nmi Diffuse reflection coefficient Specular reflection coefficient real and imaginary parts Reflected signal from facet Slope of facet along LOS Terrain type of facet Latitude of facet deg nmi Longitude of facet deg nmi Altitude of facet above sea level ft Structure Flare flight data Altitude above sea level ft Vertical component of velocity ft sec Azimuth flare to missile deg Brightness of flare watts ster Elevation flare to missile deg Flight time of flAre sec Number of flare from that launcher Latitude deg nmi Northward component of velocity knots Flag Flare launched Launch time of flare sec Longitude deg nmi Eastward component of velocity knots Range flare to missile nmi S N of flare at missile IR missile flare is directed against Magnitude of velocity knots Altitude above terrain ft Structure Flight path variables Subroutine Fly flares - 158 - FPALT npoints FPBANK npoints FPHDG npoints FPIDENT FPIHIDE npoints FPJLAST FPLAT npoints FPLFLPATH FPLONG npoints FPLOS1 FPLOSN FPMFLPATH FPNPITCH npoints FPPITCH npoints FPTIME npoints FPTIMESTEP FPVEL npoints FPYAW npoints FPZALT npoints FRQ FUNC 5 GEE GLN GRPFLG HB HF HLAT HLATO HLONG HLONGO HNPITCH i ii I IAC IAVAIL IAX IAY IBX IBY ICLUT ICXICY ID IFLG IJANUS ILLUM _RAD ILOBS IMSFD IMULT INBEAM INDX INIGHT Altitude above sea level of point on path ft Path bank angle right wing down deg Path heading deg Path identifier Path hiding parameter Index of last point on path Latitude of point on path deg nmi Number of path points per time step DT Longitude of point on path deg nmi Time of first LOS on path for JANUS sec Time of last LOS on path for JANUS sec Number of guidance time elements DTG per flight path time step Path nose pitch deg from horizontal Path pitch angle deg from horizontal Time of point on path sec Path time step sec Path velocity knots Path yaw angle deg Altitude of path point above terrain ft Frequency to set jammec String for radar functions Acceleration of gravity 32 174 ft sec 2 Glint error input to servo Flag Group maneuver Horizontal beamwidth 1 2 power points deg Choice Height-finders excluded N Hemisphere of latitude N S initial Hemisphere of longitude E W initial Subroutine Helicopter nose-nitch during climb Index General Index Search or track radars Index Aircraft in visibility file Flag Launcher availability recalculated each iteration Terrain indices for first point in FACE Terrain indices for second point in FACE Flag Clutter included Terrain indices for specular reflection point Radar identifier Flag Clutter is visible Flag Probabilities for JANUS calculated Structure Illuminator radar parameters Flag Special calculations for low observables Flag MSFD numbers in radar data Flag Multipath included Subroutine Aircraft in beam for sector scan Index for clutter element along path Flag Nighttime operation no IR or optical - INOLTFLG INTERPOL IOPT IP IPA IPG IRD IRDATA IRATNFAC 2 5 13 7 IRBRITE 15 3 IRBRITETIME 15 IRBRVEL 3 IRCDTIME 4 IRCDVEL 2 IRFLATTN 2 6 IRFLCDS 4 2 IRFLINTVAL IRFLMASS 4 IRFLREL IRFLVEL IRLIB IRRANGE 6 IRSIG IRSIGNAL 2 13 13 IRSIGNOM IRSUNATN 2 6 IRSUNSTR 2 ISA ISEEING ISNOW ISORAD ISUMMER ISUN iTX ITY IX IXC IWET j jj J JAM JAIIERLIB JD JLTYP JMBAND JLBAND JMBBDW JLBBDW JMBCODE JLBCODE JMBCOUNT JMBERP JIP xP 159 - Flag Ac has already reached destination Lnd is being checked for track assign Subroutine Interpolates aircraft position Flag Optical equipments included Number time steps per search radar print Number time steps per aircraft position print Number subdivided time steps per SAM print Index Radar in visibility file Structure IR and qptical parameters Attenuation of signal in band at range elev az Flare brightness at time and velocity watts ster Times for brightness look-up table sec Velocities for brightness look-up table knots Times for flare drag table sec Velocities for flare drag table knots Attenuation of flare signal in band at range Flare drag coefficient at time and velocity Interval between flare releases sec Flare mass at time kg Flare reliability Flare launch velocity knots File IR and opLical data Ranges for radiation look-up table nmi Subroutine Calculate IR signal Radiation in band at az and elev angles watts ster Aircraft type for radiation data Attenuation of sun in band at range Solar raaiation in band watts ster Index Communications modification Flag Exceptional seeing conditions Flag Terrain all snow covered Subroutine Pulse doppler clutter points Flag Summer seeing conditions Flag Sun visible in sky Index Terrain abscissa Index Terrain ordinate Random number generated Random number for clutter Flag Terrain wet Index General Index Aircraft Structure Jammer variables Structure Jammer libriry variables Aircraft identifier Number identifying type of jammer in library Structure Variables of individual bands Be dwidth of radiated noise MHz Coae identifying band char Nui oer of radars in band bein- jammed Effective radiated power watts - JMBFRQ JMBID JMBLFRQ JLBLFRQ JMBNUM JLBNUM JMBPAR JLBPAR JMBPOL JLBPOL JMBPROD JMBREL JLBREL JMBS JLBS JMBUFRQ JLBUFRQ JMCODE JLCODE JMDIP JLDIP JMEFF NRD JMGAIN JLGAIN JMLIB JMNBAND JLNBAND JMNHB JLNHB JMNLEAF JLNLEAF JMNVB JLNVB JMOUTBFLG NRD JMPHIN JMRDFLG NRD JMRDTECH JLRDTECH JMTACTIC NRD JREP k kk K KILLFLARE 1 11 L LAT LATMAX LATMIN LATO LINSG IT LNCIHCALC LOCATION LONG LONGMAX LONGMIN LONGO m mm M MASK MCUT MDECOY MLAT 160 - Frequency of radar being jammed MHz Identification of radar being jammed Lower frequency limit of band MHz Number identifying band Structure Jammer band variables Polarization loss dB Factor in radar equation Reliability of the jammer in that band Jammer antenna boresight angle Ist leaf deg Upper frequency limit of band MHz Code identifying jammer char Antenna dip angle deg Jamming effectiveness against radar Gain of repeater File Jammer library variables Number of frequency bands in jammer Jammer antenna horizontal beamwidth deg Number of leaves in jammer rosette antenna Jammer antenna vertical beamwidth deg Flag Radar is not in frequency coverage of jammer Angular spacing between leaf centers deg Flag That radar is being jammed Number identifying techniques jammer can use Tactic jammer is using against radar Index Monte Carlo repetition Index General Index Sites or general Subroutine Terminate flares Index General Index General Latitude for coordinate conversion deg nmi Maximum latitude of field of action nmi Minimum latitude of field of action nmi Earth latitude of center of field of action Subroutine Line of sight range azimuth elevation and if over horizon Subroutine Time and range for SAM to reach target Structure Coordinates ac radar site command site Longitude for coordinate conversion deg nmi Maximum longitude of field of action nmi Minimum longitude of field of action nmi Earth longitude of center of field of action Index General Index Command sites or general Subroutine Ground clutter masked File Ground reflection parameters Total number of decoys included Minutes of latitude - 161 - NORMV NOSHT initial Minutes of longitude initial Subroutine Monopulse antenna pattern Depression angles from ridge file Ranges from ridge file Meters to feet 3 2808333 Subroutine Calculates multipath Random number limit value 2147483647 Index General Maximum number of change points permitted 100 Maximum number of facets permitted 200 Number of flares per launcher Maximum number of masks along direction 201 Number of angles for ridges 37 Number of terrain types 9 Number of aircraft Number of aircraft surviving NAC 1 Number of BLUEMAX fixed-wing flight paths used Number of CHAMP helicopter flight paths used Maximum number of change points in profile Number of degrees of freedom for aircraft 3 5 Number of facets Number of facets in FACE subroutine Number of flight paths used total Number of subdivided time steps per full time step Subroutine Normally distributed variables for clutter Subroutine Normally distributed variables Choice - SAMs do not shoot Y NRD Number of radars - total NREP NRT NSC NSI NTAB NX NY OCCUR OPDET ORIENT OUTPUT PAINT PAST PD PHI PHIG PHIl PHIl PHI2 Number of Monte Carlo Repetitions Number of track radars Number of command sites Number of sites Line number in visibility file Number of points on terrain abscissa Number of points on terrain ordinate Time when detection occurs Subroutine Optical detection Subroutine External to boresight coordinates Subroutine Prints summaries Paint from IRLIB 2-char Past value of correlated error Probability of detection Azimuth entry for LINSGHT and ANTPAT1 deg Azimuth to true interpolated position deg corrupted Azimuthal outputs from LINSGHT deg MLATO MLONG MLONGO MONOPAT MSKDPR nmsk MSKRNG 2 nmsk MTF MULTIP M2 n nn ncp nfacet nflare nmsk nrdgangle nttype NAC NACS NAC1 NBLUMX NCHAMP NCP NDOF NF NFACET NFLPATH NGUI NORMC - PI PITCOOR PITCH PMC POINT 2 2 POWER PRBTYP PRDBN NAC PRDEND NRD 10 PRDINTNO NRD PRDMAX NRD 10 PRDMIN NRD IO PRDNUMB NRD 10 PRDPROB1 PRDPROBN PRDSTART NRD 10 PRES PRNTMOD PROFILE NCP PROFCHANGE PROFTIME PROFX PROFY PWRCLT PWRI PWR2 PO RADARLIB RAD RCLUT 2 RCTDISTRIB RDACOH NAC RDALT RDALERT RDALERTED NAC RDAMAX NAC RSAMAX 162 - 3 14159256 Subroutine Coordinates during pitch Subroutine Pitch maneuver Test value for error probability Calculation points for clutter nmi Subroutine Clutter power Choice - smooth or cookie-cutter probability of detection jamming table Structure Intervals data for JANUS End of interaction interval seu Index for interaction interval Latest end of interaction interval sec Earliest start of interaction interval sec Number of kills in interaction interval Probability of kill before first LOS Probability of kill after last LOS Start of interaction interval sec Present value of correlated error Choice - short radar printout S Structure Maneuver and cutting variables Description of maneuver 5-char Time of maneuver sec First parameter for maneuvers Second parameter for maneuvers Total power in clutter Jamming power at radar watts Atmospheric constant Structure Radar library parameters Structure Parameters for all radars Range to pulse doppler clutter Reaction time distribution N U Flag Aircraft over horizon to radar Altitude ft Flag Optical system in alert condition Flag Optical system alerted to that aircraft Maximum range against that aircraft nmi RTAMAX RIAMAX RDAFAR RSAPAR RTAPAR RIAPAR RDARMSOFF RDATSITE RDBL RDLBL RSBI RTBL RIBL RDCLAS RDCORNERANGLE 4 RDDLAT RDDLONG RDERP RDLERP RSERP RTERP RIERP RDFRQ RSFRQ RTFRQ RIFRQ RDFUNC Structure Additional radar parameters Flag ARMs aimed at radar should destruct Site at which radar is located Backlobe level dB Class - search HF acquisition track IR gun Angle - radar to four corners of terrain deg Degrees of latitude Degrees of longitude Effective radiated power watts Frequency MHz Functions performed by radar 4-char - 163 - RDGAN RDLGAN RSGAN Antenna gain dB RTGAN RIGAN RDHLAT Hemisphere of latitude N S RDHLONG Hemisphere of longitude E W RDIDENT Radar identifier Number of functions performed by radar RDIFUNC RDJMTECH RDLJTECH Most effective jamming technique RSJMTECH RTJMTECH RIJMTECH RDJPROD RSJPROD RTJPROD Factor in range equation RIJPROD RDLAT Latitude nmi File Radar library parameters RDLIB RDLFRQ RDLLFRQ RSLFRQ Lower frequency limit MHz RTLFRQ RILFRQ RDLOSS RDLLOSS RSLOSS Loss in cables and connectors dB RILOSS Name of radar type in library RDLNAME RDMAX RDLMAX RSMAX Maximum range against 1 sqm target nmi RTMAX RDJS RSMJS RTMJS RIMJS Thermal noise power watts Minutes of latitude RDMLAT RDMLONG Minutes of longitude RDMSFDNO Radar identification number in MSFD threat laydown RDNBW RDLNBW RSNBW Receiver bandwidth MHz RTNBW RINBW RDNHB RDLNHB RSNHB Horizontal beamwidth 1 2 power points deg RTNHB RINHB RDNMASK nrdgangle Number of masks in given direction RDNVB RDLNVB RSNVB Vertical beamwidth 1 2 power points deg RTNVB RINVB RDPAR RDLPAR RSPAR Structure Radar parameters RTPAR RIPAR RDPRF RDLPRF RSPRF Pulse repetition frequency Hz RTPRF RIPRF RDPW RDLPW RSPW RTPW Pulse width microsec RIPW RDRDG File Ridges produced by RJARS calculation RDRIDGDIST nrdgangle Distance to each line of sight disappearance l 2 NMASK and reappearance O in given direction nmi RDRIDGDPR nrdgangle Angle of depression to each mask deg NMASK RDRIDGFLG Flag Radar in ridge list RDSCANDIR Direction of scan RDSCANMAX Maximum angle of scan coverage deg RDSCANMIN Minimum angle of scan coverage deg RDSCANWIDTH Half-angle of scan coverage deg RDSCN RDLSCN RSSCN Scan or settling period sec RTSCN RISCN RDSECTMAX Maximum angle of sector coverage deg - 164 - Mean angle of sector coverage deg RDSECTMEAN Minimum angle of sector coverage deg RDSECTMIN Half-width of sector coverage uncued or cued deg RDSECTWIDTH 2 Scattering coefficient per unit area of RDSIGMAO nttype terrain type at radar frequency RSSIGMA0 RTSIGMAO Seconds of latitude RDSLAT Seconds of longitude RDSLONG SAM type associated with radar RDSMTYP RDLSMTYP RTSMTYP Factor in radar equation RDSPROD RSSPROD RTSPROD RISPROD Latitude deg RDTLAT Longitude deg RDTLONG RDTMAX RDLTMAX RSTMAX Maximum time target held by jammed radar RTTMAX Type of radar RDTYP RDLTYP RDUFRQ RDLUFRQ RSUFRQ Upper frequency limit MHz RTUFRQ RIUFRQ Vulnerability to ARM type RDVUL 5 RDLVUL 5 RSVUL 5 RTVUL 5 RIVUL 5 RDWPROD RSWPROD RTWPROD Factor in warning receiver equation RIWPROD Height above terrain ft RDZALT Subroutine Global to rectangular RECT Subroutine Boresight to external coordinates REORIENT Subroutine Monopulse antenna response RESPNS Radar horizon nmi RH RHL File Ridges input RIDGE Subroutine Calculates ridges RIDGES Angular spacing between ridges deg RIDGSPAC Subroutine Tests if ground visible RIDGTEST Doppler frequency of target Hz RIDOPF NAC Range output from LINSGHT RNG Interpolated true range nmi RNGG corrupted RNGI Aircraft assigned to radar RSACNO RTACNO Flag Radar assigned RSAFLG RTFLG Direction antenna is pointing deg RSANT initial RSANTO Change in antenna direction per time step RSANTCH Antenna direction incl 0 and 360 RSANTNREF Number of ARMs aimed at radar RSARMN RTARMN Azimuth error deg RSAZERR RSCLUTAZER RTCLUTAZERR Azimuth error produced by clutter deg Elevation error produced by clutter deg RSCLUTELER RTCLUTELER Signal produced by clutter dB RSCLUTSIGRTCLUTSIG Flag Radar has been killed RSDEAD RTDEAD Heading marker RSDET Elevation error deg RSELERR Far sidelobe inner limit of radar deg RSFSB - RSHITS NAC RSIFOV NAC RSISF NAC RSLOOKS NAC RSMDS RSMESSPROB RSMULTELER RTMULTELER RSNO RSNPLS RSNSTACK RDLNSTACK RSOBSTIME NAC RSPOL RTPOL RSPOSERR RTPOSERR RSREFOV NAC 10 RSRIFOV NAC 10 RSRNGERR RSSCVD RTSCVD RSSTATE RTSTATE RSTDROP NAC RSTEFOV NAC 10 RSTHRESH RSTIFOV NAC 10 RSTON RTTON RITON RSTRK RSTSUM NAC RTACQ RTACQOFF NAC 10 RTACQON NAC 10 RTALTI NGUI RTALTP 3 RTASSN NAC 10 RTAZ RIAZ RTEL RIEL RTGLNAZCOR RTGLNELCOR RTHDGP 3 RTITK NAC RTJAMFLG RTJMCNT RTJS RTLATI NGUI RTLATP 3 RTLONGI NGUI RTLONGP 3 RTMHSB RTMVSB RTOFF NAC 10 RTOUTPUT RTPAST RTPHIACC 165 - Number of successful detections Flag Aircraft in field of view of radar Index - number times in field of view Number of times radar scans over aircraft Receiver processing gain dB Probability of receiving alerting message Error in elevation produced by multipath deg Search radar number for given radar number Number of pulses reflected from target Number of stacked beams in antenna pattern Duration of observation by optical system sec Polarization of signal H V Position error ft Range at exit from field of view nmi Range at entry into field of view nmi Range error ft Subclutter visibility dB Structure State of radar Time to drop detection hold sec Time to exit field of view sec Threshold level watts Time of entry into field of view sec Time radar comes on in indicated state Tracker associated with acq radar Number of successive detections Acq radar associated with tracker Time acq radar goes off sec for output Time acq radar comes on sec for output Interpolated corrupted target altitude ft Corrupted altitude now and last two ft Time tracker assigned sec for output Azimuth of tracker deg Elevation of tracker deg Correlated azimuth Correlated elevation Corrupted heading now and last two deg Index Number times tracker assigned to aircraft Flag Tracker is being jammed SAM launched Number time steps tracker has been jammed SAM not launched Signal noise ratio at intercept Interpolated corrupted latitude deg Corrupted latitude now and last two deg Interpolated corrupted longitude deg Corrupted longitude now and last two deg Maximum azimuthal servo bandwidth Hz Maximum elevation servo bandwidth Hz Time tracker goes off sec for output Structure Tracker summary variables Structure Tracker past variables Azimuthal acceleration deg sec sq - RTPHIP 3 RTPITCHP 3 RTREASSN RTRNGACC RTRNGP 3 RTSRB 3 RTTHAZCOR RTTHELCOR RTTHETAACC RTTHETAP 3 RTTHRNGCOR RTTIMNRA RTTIMNRNA RTTIMRA RTTIMRNA RTTON NAC 10 RTVELP 3 Rl R2 R90 R270 srchno str 4 SAMACC SAMLIB SCALEH SCENA SDL SECTASS SECTSCAN SEED SEEKER SEKRPAT SIGMA SIGMAI SIGMA2 SIGNAL SIMPLE-SAM SITE SIALERT NAC SIALT SICOMFLG SIDEAD SIDLAT SIDLONG SIDNDLY SIHLAT SIHLONG SIIDENT SILAT SILONG SIMESSPROB SIMLAT 166 Azimuth past values deg Corrupted pitch now and last two deg Flag Tracker reassigned Range acceleration nmi sec Past values of range nmi Servo bandwidth 3 channels Hz Correlated azimuth error from noise deg Correlated elevation error from noise deg Elevation acceleration deg sec Past elevation deg Correlated range error from noise nmi Time tracking - no range angle sec no range no angle sec range angle sec range no angle sec Time tracker comes on sec for output Corrupted velocity now and last two knots Range outputs from LINSGHT Constants used in RECT Maximum number of times in view 10 Radar type for graphics Subroutine SAM acceleration Structure SAM library variables Atmospheric scale height 34174 ft File Scenario for simulation Sidelobe attenuation level dB Subroutine Sector assignment Subroutine Sector scanning Starting value for random number generator Structure Seeker parameters Subroutine Seeker antenna pattern Radar cross section Subroutine Calculate radar cross section Radar cross section output from SIGMAI Reflected power received from target Structure SAM variables Structure Site variables Flag Site alerted to that aircraft Altitude above sea level ft Flag Communications operating Flag Site not operating Degrees of latitude Degrees of longitude Delay on downward communication link sec Hemisphere of latitude N S Hemisphere of longitude E W Site identification number Site latitude nmi Site longitude nmi Probability of receiving message Minutes of latitude - 167 - SISLAT SISLONG SITLAT SITLONG SIUPDLY SIZALT SIZE SJ1 SJ2 SKAIMERR SKAMBIG SKATTNMX SKAUTON SKAZ 2 SKAZCOM 3 SKAZSK 3 SKBL SKCLLEN SKCLLTSIG SKDELTAF SKDFILTW SKDOPFTM SKELCOM 3 SKELEV 2 SKELSK 3 SKFLRJCT 2 NFLARE SKFLRJCTPROB SKFLRJCTFIME SKFOV SKFOVO SKIN'TFAC 2 SKIN'TERF 2 SKIRTYP SKJS Minutes of longitude Flag Site capable of motion Flag Site actually moving Number of search radars at site Number of track radars at site Number of assigned track radars at site Best data on ac altitude at isolated site Flag Data to pass Best data on ac latitude at isolated site longitude Command site to which site reports Sequence number matching identification number in list of radars at site Seconds of latitude Seconds of longitude Latitude deg Longitude deg Delay on upward communication link sec Altitude above terrain ft Character for number of change points S M L Signal to noise ratio RMS aiming error for guns deg Ambiguous range of pulse doppler nmi Maximum attenuation of doppler filter dB Flag 1 if autonomous Azimuth present and past deg Azimuth command now and last two deg Azimuth from boresight now and last two deg Seeker backlobe level dB Length of clutter element nmi Signal from clutter dB Doppler bank filter width Hz MTI filter width Hz Doppler frequency target to missile Hz Elevation command now and last two deg Elevation present and past deg Elevation from boresight now and last two deg Rejection state of flare from launcher 0 or 1 Probability of rejecting a flare Time for decision to reject flare sec IR seeker field of view deg Optical field of view deg Factor in blink jamming equation Power in blink jamming watts Short or long wavelength band Jammer signal ratio SKKSERV Locke's K parameter SKLOCK SKLRATL SKMAGNIFY SKNHB Full partial or no lock Minimum S N for seeker motion dB Magnification of optical system Seeker horizontal beamwidth deg SIMLONG SIMOBILE SIMOVING SINRSSI SINRTSI SINRTSIA SIPSALT NAC SIPSFLG NAC SIPSLAT NAC SIPSLONG NAC SIRPT SIRSSIID SIRTSSID - 168 - SKNOISE SKNSERV SKNVB SKRATLMX SKROLOFF SKSCON 2 SKSERVCON 5 SKSIGFAC SKSIGNAL SKSIGNOI SKTFDWELL SKTHRESH SKTYPE SKURATL SKWSERV SKXNEI SKYGROUND 2 2 SLAT SLATO SLONG SLONGO SLTYP SMALT SMAREF SLAREF SMAVAIL SMAZ SMAZPM 2 SMAZPRO 2 SMAZT 4 SMCDl 4 3 SLCDl 4 3 SMCD2 4 3 SLCD2 4 3 SMCEP SLCEP SMCOUNT SMELEV SMELEVPM 2 SMELEVPRO 2 SMELEVTM 4 SMFUZRNG SMFUZTYPE SMGUICL SLGUICL SMGUIGAN SLGUIGAN SMHDG 2 SMHMAX SLHMAX SMHMIN SLHMIN SMINT 20 SMINTR 20 SMIN-1T 20 Noise incl jamming at receiver watts Locke's N parameter Seeker vertical beamwidth deg Maximum rate of seeker motion deg sec Rate of attenuation dropoff in filter bank Monopulse receiver constants Servo response constants Factor in signal equation Signal at receiver watts Signal noise ratio Time optical system dwells on target sec Threshold signal noise ratio Pulse doppler or CW S N required to maximum seeker motion dB Locke's W parameter IR noise equivalent input watts Sky ground ratio for optical Seconds of latitude initial Seconds of longitude initial Type of SAM Altitude ft Reference area sqm Flag SAM is operating Azimuth - launcher to SAM deg Azimuth - SAM to partner now and last deg Azimuth - SAM to target projected position now and DTG ago deg Azimuth - SAM to target now two previous times and true deg Constants in coefficient of drag expression Dispersion of SAM guidance system ft Number of SAMs fired from launcher Elevation - launcher to SAM deg Elevation - SAM to partner now and last deg Elevation - SAM to target projected position now and DTG ago deg Elevation - SAM to target now two past and true deg Fuze range ft Fuze type 0 contact 1 proximity Guidance class A C S I Gain in guidance loop Heading of SAM - now and DTG ago deg Maximum operating altitude ft Minimum operating altitude ft Outcome of interception for output Range at intercept nmi for output Time of intercept sec for output - SMJAMSUSC 2 20 SLJAMSUSC 2 20 SMJAMTYP 2 20 SLJAMTYP 2 20 SMJSCRIT 20 SLJSCRIT 20 SMKPROB 20 SMKRMAX SLKRMAX SMKRMIN SLKRMIN SMLAGCON 4 SMLAT SMLIB SMLNCFLG SMLNCHD SMLOFT SLLOFT SMLOFTRT SMLONG SMLREL SLLREL SMLSUC 20 SMLTIME 20 SMMACHT 4 3 SLMACHT 4 3 SMMASS SMMASSRT 4 SLASSRT 4 SMMASSO 4 SLMASSO 4 SMMISSD 20 SMMNVEL SMMOBLTY SLMOBLTY SMNRT SLNRT SMNRTA SMNSTO SLNSTO SMNSTOA SMNSUSC 2 SLNSUSC 2 SMOUTPUT SMPITCH 2 SMPITCOM 2 SMPRNT SMPROPUL SLPROPUL SMRBECO SLRBECO SMRINT SMRMAX SLRMAX SMRMIN SLRMIN SMRNG SMRNGPM 2 SMRNGTM 3 SMRSECO SLRSECO SMSTAGE SMSTATE SMSYSREL SLSYSREL 169 - Susceptibility to tnat jammer in each table Type of jammer for effectiveness tables Critical S N for that jammer Kill probability at intercept for output Radius Kill prob 0 outside ft Radius Kill prob warhead reliability inside it ft Constants in guidance lag equation Latitude nmi File SAM variables Flag SAM preparing for launch Flag SAM launched Initial loft angle deg Rate of decrease of pitch in boost deg sec Longitude nmi Launch reliability Launch outcome SUCCESS FAILURE for output Time of launch sec for output Transition value of Mach number Present mass of SAM kg Mass flow rate of each stage kg sec Initial mass of each stage kg Miss distance at intercept ft for output Mean velocity fps Used in LNCHCALC Probability SAM is mobile Number SAMs initially available at launcher Number SAMs presently available at launcher Number SAMs initially in storage at launcher Number SAMs presently in storage at launcher Number of jammers with data in tables Structure Output summary variables Pitch angle of velocity Now and DTG ago deg Pitch command now and past Choice - print SAM data each IPG'th subdivided time step Y Structure Propulsion variables Range at booster cutoff nmi Range at intercept nmi Maximum operating range nmi Minimum operating range nmi Range launcher to SAM nmi Range to partner now and previous nmi Range SAM to target - past present true nmi Range at sustainer cutoff nmi Present stage of SAM Character giving SAM state A F P B I S C R E Overall system field reliability - SMTBECO SLTBECO SMTGT 20 SMTHRUST 4 SLTHRUST 4 SMTIMCON SLTIMCON SMTINT SMTINTER SLTINTER SMTLNCH SMTMAX SLTMAX SMTRCT SLTRCT SMTRCTMAX SLTRCTMAX SMTRCTMEAN SMTRCTMIN SLTRCTMIN SMTRCTO SMTRCTSD SMTREF SLTREF SMTREFMAX SLTREFMAX SMTREFMEAN SMTREFMIN SLTREFMIN SMTREFO SMTREFSD SMTRLD SLTRLD SMTRST SMTSECO SLTSECO SMVEL SMWREL SLWREL SMYAWCOM 2 SMZALT SPHER SRBMOD SRCHRAD SRVERR SRVERRCOR STORE STIDENT STLENGTH STRX STRY SUMCLT SUMMARY SUMSIG SYNEX SYNEY toff ton trans trkno T TC TCKERR 4 TDAY TEALT 170 - Time of booster cutoff sec SAM target aircraft for output Thrust of each stage Newtons Time constant for guidance lag Time of intercept sec Duration of interstage interval sec Time of launch sec Maximum flight time till self-destruct sec Reaction time - first launch against ac sec Maximum reaction time for distribution sec Mean reaction time for distribution sec Minimum reaction time for distribution sec Initial reaction time sec Standard deviation for distribution sec Reaction time - refiring against ac sec Maximum refire time for distribution sec Mean refire time for distribution sec Minimum refire time for distribution sec Initial refire time sec Standard deviation for distribution sec Reload time - storage to launcher sec Restart time after reloading sec Time of sustainer cutoff sec Velocity fps Warhead reliability Yaw command now and past Altitude above terrain ft Subroutine Rectangular to global Choice - adaptive or fixed servo bandwidth A F Structure Search radar parameters Subroutine Uncorrelated errors Subroutine Correlated errors Structure Storage for flight paths Stored flight path identifier Stored flight path number of points Global longitude variable in ZTERN Global latitude variable in ZTERN Clutter in monopulse sum channel Structure Search radar summary variables Sum channel output for monopulse receiver Directions for clutter path Time of visibility end in file sec Time of visibility start in file sec Type cast from character to float Maximum number of times in view 10 Simulation time sec Counter for maneuvers Tracker error - range ft azimuth and elevation deg position ft Time of day hr Altitude of terrain point above sea level - TEMP TEMP1 TERMINATE TERRA TERRAIN 2 NX 3 2 NY 3 TETYP TFIN THETA THETAG THETAI THETA1 THETA2 TL TOFF TON TRACKON TRKRAD TRALT TRDR TRDX TRDY TRINDEX TRLAT TRLGMAX TRLGMIN TRLONG TRLTMAX TRLTMIN TRPAR nttype TRPA TRPB TRPC TRPCODE TRPD TRPEPSI 2 TRPEPSR 2 TRPFRESCO 2 2 TRPREFL TRPROUGH TRPTYPE TRTYP TRX TRY TSAM TTC TURN TYPE 5 TO UNIV UNIVC UPDAC UPDAR 171 - Dummy calculation variables Subroutine Eliminate aircraft if outside terrain File Terrain data Structure Terrain data Terrain type Final time of simulation sec Input elevation for LINSGHT and ANTPATI Interpolated elevation to true position deg corrupted Elevation outputs from LINSGHT Time of SAM launch sec Time visibility ceases - from file sec Time visibility begins - from file sec Subroutine Turn tracker on Structure Track radar variables Altitude of terrain point above sea level ft Diagonal terrain step nmi or deg Terrain abscissa step nmi or deg Terrain ordinate step nmi or deg Subroutine Finds terrain indices Latitude of terrain point deg nmi Maximum longitude of terrain point deg nmi Minimum longitude of terrain point deg nmi Longitude of terrain point deg nmi Maximum latitude of terrain point deg nmi Minimum latitude of terrain point deg nmi Structure Terrain parameters Parameter A in terrain radar cross-section Parameter B in terrain radar cross-section Parameter C in terrain radar cross-section Terrain type description Parameter D in terrain radar cross-section Imaginary part of dielectric coeff dry wet Real part of dielectric coefficient dry wet Real and imaginary parts of Fresnel coefficient dry wet Visible reflectivity RMS roughness parameter cm Index Terrain type Type of terrain element Terrain longitude used in TRINDEX Terrain latitude used in TRINDEX Subdivided time for SAM calculations sec Time counter Subroutine Turn calculation String for radar types Atmospheric constant Subroutine Uniformly distributed variables Subroutine Uniform distribution for clutter Subroutine Aircraft Subroutine Anti-radiation missiles - 172 - UPDCK Subroutine System clock UPDLY NSI Uplink delay from site to command site sec UPDMC Subroutine Monte Carlo UPDRS Subroutine Search radars UPDRT Subroutine Track radars UPDSI Subroutine Sites UPDSM Subroutine Surface-to-air missiles UPDTR Subroutine Terrain UPDWR Subroutine Warning receivers varO varl var2 var3 Dummy calculation variables var4 var5 var6 var7 var8 var9 varlO varll varl2 VAR1 VAR2 VAR3 VAR4 Dummy calculation variables VAR5 VAR6 VAR7 VAR8 VAR9 VARIO VARlI VAR12 VB Vertical beamwidth input for ANTPAT1 deg VEL Velocity input for SAMACC fps VELAPP Cosine of angle between ac velocity and line of sight VIS Choice - terrain mode VISDATA NAC NRD VISKEY VISTOFF 20 VISTON 20 VSND WARNING-RECEIVER WARNINGRECEIVERLIB WLTYP WRBAND WLBAND 20 WRBCODE WLBCODE WRBCOUNT WRBGAN WLBGAN WRBID 20 WRBLFRQ WLBLFRQ WRBNUM WLBNUM WRBPAR WLBPAR WRBS WLBS WRBSENS WLBSENS WRBUFRQ WLBUFRQ WRDIP WLDIP WRJMOFF WRJMON WRLIB WRNBAND WRLBAND WRNHB WLNHB WRNLEAF WLNLEAF WRNVB WLNVB WRPHIN WRRDFLG NRD Structure Visibility data Key for visibility data sequence on each pair Time aircraft ceases to be visible to radar Time aircraft becomes visible to radar Velocity of sound fps Structure Warning receiver variables Structure Warning receiver library Type of warning receiver Structure Frequency band variables Band identifying code char Number of received signals in band Antenna gain in band dB Identification of radar in list in band Lower frequency limit of band MHz Number of band Structure Band parameters Angle from nose of first rosette leaf deg Sensitivity of band receiver dB milliwatt Upper frequency limit of band MHz Elevation boresight of antenna deg up Subroutine Turns jammer off Subroutine Turns jammer on File Warning receiver library Number of frequency bands in a receiver Horizontal beamwidth of rosette leaf deg Number of leaves in rosette Vertical beamwidth of rosette leaf deg Angle between azimuth leaf boresights deg Flag Radar has been detected and catalogued Subroutine Turns warning receiver off Input variable for subroutines WRRECOFF X - 173 - XA XCLUT 2 XG XL XMOM 2 XR XRC X1 X2 XD Y YCLUT 2 YFL YG VL Elliptical angle for ANTPAT1 Longitudes for pulse doppler clutter points nmi Longitnde for clutter point nmi Longitude reference point for multipath nmi Longitude moment of clutter Variable for random numbers double precision Variable for clutter random number Dummy longitudes for clutter nmi Input variable for subroutines Latitudes for pulse doppler clutter points nmi Uniformly distributed variable from UNIV Latitude for clutter point nmi Latitude reference point for multipath YMOM 2 YNC 2 2 Yl Y2 YD Z ZL ZTERN ZTRX ZTRY Latitude moment for clutter Slopes for cluttei lines Dummy latitudes for clutter nmi Output variable from ZTERN Altinude of multipath r f-rence point ft Subrcutine Calculates height of terrain Longitudinal variable in ZTERN Latitidinal variable in ZTERN - 175 - Appendix FLOW CHARTS Following a suggestion of the reviewer a set of flow charts is included in this appendix to show the operation of the program in graphic form The charts are arranged so that a block on the chart usually represents a block of code that performs the operation described in the words accompanying the block The first chart Fig A 1 gives the Gverall structure of RJARS and the remaining charts Figs A 2 A 13 show in greater detail the actions in each functional block of Fig A l In the author's view the charts can best be used by referring to them while reading the text - 176 - RJARS Main program GETDATA Input all data VIS 4 or read error F T Last repetition F iUPDOK I Clock UPDAC Aircraft UPIDTR Terrain visibility UPDRS Search and acquisition UPDSI Sites tracker assignment UPDRT Trackers UPDAR Anti-radiation missiles SUPDSM I Surface-air missiles and guns UPDWR Warning receivers 4 TNot final time aircraft surviving OUTPUT Summaries UPDMC Monte Carlo reinitializing Fig A 1-RJARS flow chart - 177 - Sequence and input file 1 2 3 4 5 6 7 8 9 10 11 12 13a 13b 14 15 16 Initialization constants Terrain data Aircraft scenario Aircraft physical data Aircraft radar cross-section Anti-radiation missile data Jammer equipment data Warning receiver equipment data Flight profile Flight path data Infrared equipment and radiation data Radar scenario Radar ridge data Radar ridge calculation Radar equipment data Site and command site data Surface-air missile data Fig A 2-GETDATA sequence chart SCENA TERRA SCENA ACLIB ACRCS ARLIB JMLIB WRLIB SCENA BLUMX CHAMP IRLIB SCENA RIDGE SCENA TERRA RDLIB SCENA SMLIB - 178- SUPDCK Increment simulation time UPDAC Cycle over aircraft and communications Following flight planner T F Update postion Update flight path qr Continue current maneuvers Test if outside terrain Update past values Update decoys Perform new flight instructions Perform new communications instructions Test for crashes I Fly previously launched flares Output aircraft location Return Fig A 3-Update clock UPDCK and update aircraft UPDAC flow chairt - 179 - UPDTR T F VlS 1 Cycle over Read current visibility data aircraft Cycle over radars Mutu a 'I es of sight E Fig A 4-Update terrain UPDTR flow chart File and print visibility data - 180 - UPDRS Cycle over radars Check survival Cycle over aircraft Check intervisibility Is searcher radar Update optical search and acquisition Fig A A Update radar search and acquisition Fig A 5 Fig A 5-Update searchers UPDRS flow chart 181 - UPDRS optical Searcher cued by F communications alert T Reset scan limits qr Optical sector scan Entered or left field Search detection algorithm Target detected while in F search T Enter acquisition Acquisition detection algorithm Target recognized Turn tracker on Search detection algorithm Target detected F Revert to search Return Fig A 6-Update optical search and acquisition flow chart - 182 - UPDRS radar SDrop acquisition under criteria E Update antenna position SSet backlobe canceller I Jamming strobe widths I Aircraft entering or leaving field STarget in main beam II Radar cross section and signal Multipath Z I Jamming power filtering SClutter Probability of detection I FI Target detected Drop target if past hold time Range and angle errors I711 Printouts L Detection table Turn tracker on if called mReturn Fig A 7-Update radar search and acquisition flow chart - 183 - UPDSI trackers in use FAll Cycle over isolated Cycle over command I sites sitesF es tata eac h Bstata Cycle over Best data each aircraft t Bodataet Broadcast alerts trackers Assignment criteria Assignment decisions Cycle over reporting sites ICycle over trackers Assignment criteria Assignment decisions Alert and cue optical searchers Return Fig A 8-Update sites UPDSI flow chart - 184 - UPDRT Cycle over trackers Check intervisibility Conditions for dropping track Tracker is radar Tracker is IR lR signal sina Optical signal Tracker signal s T P ultipath Seeker signal Maintained lock T Clutter Tracking accuracy J Revert to acquisition power Adaptive servos Signal noise filtering Tracking errors Breaklock tests Printouts Interpolation L I Fig A 9-Update trackers UPDRT flow chart Return - 185 - UPDAR Cycle over aircraft Anti-radiation missiles on board Am I being tracked Should ARM be launched I Fly ARM Will ARM kill radar Drop ARMs aimed at dead radar Return Fig A 10-Update anti-radiation missiles UPDAR flow chart - 186- UPDSM Cycle over launchers State A or F should SAM be launched Z I State P launch when ready Cycle on subdivided time Update position and velocity A Semiactive seeker IR seeker IR signal Seeker signal Launch and fly Seeker clutter flares Seeker jamming Flare signal Guidance command Guidance command Guidance class Proportional navigation Unguided T Steer toward projected intercept Printouts Call endgame Endgame Outcome decision Any missiles left at launcher Return Fig A 11-Update surface-to-air missiles UTPDSM flow chart - 187 - UPDWR Cycle over aircraft Cycle over radars Power received F Exceeds sensitivity New signal Search radar in beam T T Catalog signal Turn jammer off Unzatalog signal R Should it be jammed Turn jammer on Return Fig A 12-Update warning receivers UPDWR flow chart - 188 - Output Search and acquisition summary Tracker summary Surface-air missile summary SAM box score Anti-radiation missile summary Aircraft survivability summary Aircraft box score Statistics UPDMC Reinitialize all variables except random number generator Recalculate availabilities if required Fig A 13-Output and Monte Carlo UPDMC flow chart - 189 - REFERENCES 1 Hubbs J E The Jamming Aircraft and Radar Simulation JARS Program Naval Warfare Analysis Division Johns Hopkins University Applied Physics Laboratory Report NWA-83-017 Laurel MD May 1983 2 Hubbs J E and G W Loughran The Modified Jamming Aircraft and Radar Simulation JARSM Program Naval Warfare Analysis Division Johns Hopkins University Applied Physics Laboratory Report NWA-84-027 Laurel MD May 1984 3 Sollfrey W RJARS RAND's Version of the Jamming Aircraft and Radar Simulation The RAND Corporation N-2727-AF Santa Monica CA December 1988 4 Skolnik M I Radar Handbook McGraw-Hill Book Co New York NY 1970 5 Barton D K Radar Systems Analysis Artech House Inc Dedham MA 1976 6 Baty R S et al Enhanced Surface-to-Air Missile Simulation ESAMS Computer Program - Analyst Manual Basic Methodology Flight Dynamics Laboratory Air Force Wright Aeronautical Laboratories Air Force Systems Command Wright-Patterson Air Force Base OH 45433 Auigust 1988 Report prepared by Booz-Allen Hamilton Inc Report AFWAL-TR-88-3051 Beavercreek OH