The complexity and performance characteristics of weapon systems under development by the Ballistic Missile Defense Organization (BMDO) require an integrated test approach that spans all levels of testing. Flight testing of ballistic missile interceptors is limited by the complexity and costs of the exercises and are constrained by inherent restrictions imposed by test ranges. While flight testing remains an essential part of ballistic missile interceptor test programs, other test methods must be utilized to fully characterize system operational characteristics. The BMDO uses a test concept which employs specialized facilities to address critical aspects of the ballistic missile defense (BMD) engagement process. The facilities are used during all phases of the acquisition life cycle, accommodating test articles ranging from early prototype subsystems to integrated production-like systems. Individually, these facilities characterize the performance of the specific unit under test. Collectively, these facilities span the BMD engagement process from target detection through kill assessment. Test results are consolidated to characterize the performance of the integrated system. In this manner, the performance of the system is characterized throughout its potential performance envelope. This paper discusses the role and contribution of infrared space-based surveillance and kinetic kill interceptor hardware-in-the-loop (HWIL) facilities in BMD test programs. An overview of BMDO HWIL test policy and sponsored facilities is presented. This paper examines the relationship between BMDO sponsored facilities in terms of inputs required to support HWIL tests and HWIL outputs available to support other tests. Issues pertinent to planning and executing a successful HWIL program are also discussed.

This paper describes Hardware-In-The-Loop simulation as practiced at the U.S. Army Missile Command Advanced Simulation Center (ASC) located at Redstone Arsenal, Alabama. An overview of several of the simulators operated at the ASC is followed by a discussion of the role of simulation in the missile system development process. The paper concludes with a summary of the Verification and Validation methodology employed for a typical hardware-in- the-loop simulation.

During the past two to three decades, weapon systems have become so complex, sophisticated and costly, that traditional flight test methods have become inadequate as a means to provide a true measure of a systems performance capabilities or limitations. Non-destructive laboratory simulation, utilizing actual flight hardware as an integral part of the simulator test configuration, has evolved into a very practical and cost-effective method for evaluating weapon systems performance. The challenge faced by simulation engineers is how to plan for, provide and maintain simulator capabilities and fidelity which are a step ahead of the test article technology. This paper attempts to list and describe some of the lessons learned in developing, upgrading and operating hardware-in-the-loop simulator facilities used for simulation testing of weapon systems at Eglin Air Force Base, Florida.

Hardware-in-the-loop (HWIL) simulations are making large contributions to Navy development and operational testing as well as to research and development. This paper describes several of the major HWIL facilities, their simulation capability, and the contribution they have made to Navy test and evaluation in recent years. The paper also discusses future opportunities for using hardware-in-the-loop simulations with other types of simulations to increase test and evaluation capabilities, reduce costs, and shorten test time.

The degree to which hardware-in-the-loop tests can be used to replace more expensive flight tests is dependent on how well the tests resemble real flight tests. One of the most challenging problems associated with making realistic hardware-in-the-loop tests is the projection of realistic imagery to the seeker. Since a seeker is limited in its ability to `see' a real scene, projection systems do not have to perfectly replicate real scenes. They only have to produce scenes which appear the same as the real scenes when measured with spatial, spectral, and temporal resolutions that are at least as poor as those of the seekers to be tested. Unfortunately, this means that in order to determine the realism of a given test or class of tests, it is necessary to include in the analysis characteristics of the seekers as well as characteristics of both the real scenes and the projected scenes. For many reasons, the conventional Fourier transform techniques are not adequate for performing these analyses. In this paper, a formalism is given for analyzing spatial, spectral, and temporal effects in a hardware-in-the-loop system involving a pixelized projector and a passive imaging sensor. The fundamental equations are presented describing the measurement of either a real scene or a pixelized projector with a passive imaging sensor. The equations are kept in the space, wavelength, and time domains to avoid the unnecessary restrictions that are encountered when transforming to the Fourier domain. An example is given of an application of the formalism to evaluate the effects of projector pixel spacing and blur effects.

The ability to thoroughly exercise and accurately predict the missile and/or submunition hardware and on-board software in a laboratory environment has always been preferred to reduce the number and costs of actual flight tests, to increase the probability of success of flight test using hardware-in-the-loop (HWIL) simulation, and help assure the U.S. Army is a `smart' buyer. The U.S. Army Missile Command, responsible for providing all the simulation support for the U.S. Army's guided missiles and submunitions, has developed a HWIL Simulation Facility that supports several HWIL techniques including real time, closed-loop, `seeker-in-the-loop', `processor-in-the-loop', and `man-in-the-loop'. This paper provides an overview of the development, operation, and usage of one such HWIL facility called the Imaging Infrared System Simulation. The major technological components used to develop the IIRSS are presented individually and integrated as an integration and performance-level HWIL system simulation.

An addressable mosaic array of resistively heated microbridges offers much flexibility for infrared scene simulations. In the Wide Band Infrared Scene Projector program, Honeywell has demonstrated high yield arrays up to size 512 X 512 capable of room temperature operation for a 2 band infrared projection system being designed and built by Contraves Inc. for the Wright Laboratory Kinetic Kill Vehicle Hardware In-the-Loop Simulator facility at Eglin Air Force Base, FL. The arrays contain two different pixel designs, one pixel designed for kHz frame rates and high radiance achieved at a power level of 2.5 mWatts/pixel and the other pixel designed for more moderate 100 Hz frame rates at lower radiance and at maximum power levels of 0.7 mWatts/pixels. Tests on arrays and pixels have demonstrated dynamic ranges up to 850:1, radiance rise times on the order of 2 mseconds, and broadband pixel emissivities in the range of 70%. Arrays have been fabricated with less than 0.1% pixel outages and no row or column defects. These arrays are mounted in a specialized vacuum assembly containing an IR window, vacuum package, cooling block, and pump out manifold.

Kinetic Energy Weapon (KEW) programs under the Ballistic Missile Defense Office (BMDO) need high fidelity, fast framing infrared (IR) imaging seekers. As imaging sensors have matured to support BMDO, the complexity of functions assigned to KEW weapon systems has amplified the necessity for robust hardware-in-the-loop (HWIL) simulation facilities to reduce program risk. The IR projector, an integral component of a HWIL simulation, must reproduce the real world with enough fidelity that the unit under test's software will respond to the projected scenario of images as though it were viewing the real world. The MOSFET resistor array IR scene projector shows great promise for both cryogenic vacuum chamber and room temperature testing. The resistor array breaks up the analog world into discrete pieces, much like a focal plane array (FPA). Extensive debate has taken place since the inception of the resistor array as to how many resistors need to be projected into one FPA detector. Can one resistor be matched to one FPA detector, or does the Nyquist rate of at least 2:1 sampling take precedence? Testing was accomplished at the Wright Laboratory Kinetic Kill Vehicle Hardware-in-the-Loop Simulator that utilized a 5:1 zoom collimator and the Wideband Infrared Scene Projector resistor array to project in the 1:1, 1.3:1, 2:1, and 3:1 cases. This paper discusses the results of those tests.

This paper describes the current design characteristics and performance capabilities of the US Army Missile Command's diode laser based infrared scene projector technology. The projector is now operational at the US Army Missile Command's Research, Development, and Engineering Center and is being integrated into several HWIL simulation facilities. The projector is based upon a linear array of Pb-salt diode lasers coupled with a high-speed optical scanning system, drive electronics and synchronization electronics. The projector design has been upgraded to generate 256 X 256 resolution scenes at 4 KHz frame rates, and the fabrication of a 544 X 544 projector is in progress. The projector system now includes real-time non-uniformity correction electronics and is interfaced with a real-time scene generation computer. In addition, a closed-cycle cryogenic cooling system has been added for increased dynamic range and maintenance-free operation. The system's modularity provides upgradability to meet specific performance requirements such as increased spatial resolution, different emission wavelengths, or dual-band scene projections. The projector's upgraded design and performance characteristics are presented in this paper, as well as sample images generated with the projector and captured by an InSb FPA sensor.

The Air Force Development Test Center's (AFDTC) Guided Weapons Evaluation Facility (GWEF), is designed to test guided munitions performance using Hardware-In-the-Loop simulations. Evaluation of imaging infrared guided munitions requires the generation and projection of complex infrared (IR) `fly-in' scenes to the unit under test which is mounted to a flight motion simulator. Members of AFDTC's 46 Test Wing and Avionics Systems Command's Wright Labs have teamed to develop and integrate this capability within the GWEF and Wright Lab's Kinetic Kill Hardware-In-the-Loop Simulation (KHILS) facility. The major Hardware-In-the-Loop (HIL) components for the GWEF include an IR scene generator, an IR projector, a five axis flight motion simulator (FMS), a 6 degree of freedom missile flight simulation, and the opto- mechanical interface to mount the projector onto the 5 axis FMS. GWEF's unique HIL solution is utilizing the 512 X 512 resistor array technology developed by KHILS, and off- the-shelf state-of-the-art scene generation computer, FMS, and optics. Details on this in-house development effort include acquisition and configuration/integration issues, thermal information to radiance bandpass output validation, IR scene generation and frame latency, generated IR scene input to projected output calibration, and simulation guidance from launch to impact verification. This capability has been successfully integrated into the GWEF, meeting a March 1996 HIL test.

Real-time infrared (IR) scene generation for HardWare-In- the-Loop (HWIL) testing is a complicated problem. As a consequence, real-time signal phenomenology and real-time sensor effects modeling have been difficult to accomplish. For example, modern systems are burdened with designation, discrimination, identification, tracking, and aimpoint selection tasks. This requires that sensor data rates increase and therefore faster computations for real-time scene generation systems are necessary in testing environments. Moreover, commercial scene generation hardware is rapidly improving making it a viable solution for HWIL applications in the Kinetic Kill Vehicle Hardware-in-the- Loop Simulator facility. This paper presents the primary analysis performed to determine the strengths and weaknesses of using commercially available hardware and software for real-time scene generation in support of HWIL testing. Finding the appropriate solution to real-time IR scene generation requires striking a balance between physical accuracy and image framing rates. This effort is to determine rendering accuracy and speed for target models which begin as a point source during acquisition and develop into an extended source representation during aimpoint selection.

As cost becomes an increasingly important factor in the development and testing of IR seekers, the need for accurate hardware-in-the-loop simulations is critical. In the past, expensive and complex dedicated scene generation hardware was needed to attain the fidelity necessary for accurately testing IR seekers. Recent technological advances and innovative applications of established technologies are beginning to allow development of cost effective replacements for dedicated scene generators. These new scene generators are mainly constructed from commercial off-the- shelf (COTS) hardware and software components. At the U.S. Army Missile Command researchers have developed such a dynamic IR scene generator built around COTS hardware and software. The scene generator is being used to provide inputs to an IR scene projector for in-band seeker testing and for direct base band signal injection into the seeker electronics. Using this low cost scene generator, up to 120 frames per second of 12-bit intensity images are being generated at 640 by 640 pixel resolution. The scene generator compensates for system latency using a special purpose hardware component implemented on a single VME card. Multiple dynamic targets, terrain, and effects are configured and controlled by the facility simulation computer via a shared memory interface to the scene generator.

This paper describes the techniques which have been developed for an infra-red (IR) target, countermeasure and background image generation system working in real time for HWIL and Trial Proving applications. Operation is in the 3 to 5 and 8 to 14 micron bands. The system may be used to drive a scene projector (otherwise known as a thermal picture synthesizer) or for direct injection into equipment under test. The provision of realistic IR target and countermeasure trajectories and signatures, within representative backgrounds, enables the full performance envelope of a missile system to be evaluated. It also enables an operational weapon system to be proven in a trials environment without compromising safety. The most significant technique developed has been that of line by line synthesis. This minimizes the processing delays to the equivalent of 1.5 frames from input of target and sightline positions to the completion of an output image scan. Using this technique a scene generator has been produced for full closed loop HWIL performance analysis for the development of an air to air missile system. Performance of the synthesis system is as follows: 256 * 256 pixels per frame; 350 target polygons per frame; 100 Hz frame rate; and Gouraud shading, simple reflections, variable geometry targets and atmospheric scaling. A system using a similar technique has also bee used for direct insertion into the video path of a ground to air weapon system in live firing trials. This has provided realistic targets without degrading the closed loop performance. Delay of the modified video signal has been kept to less than 5 lines. The technique has been developed using a combination of 4 high speed Intel i860 RISC processors in parallel with the 4000 series XILINX field programmable gate arrays (FPGA). Start and end conditions for each line of target pixels are prepared and ordered in the I860. The merging with background pixels and output shading and scaling is then carried out in the FPGA's on a line by line basis. The whole process is carried out at 4 * 4 super-sampled rates to minimize spatial aliasing. Other techniques such as real time selective image filtering will be described and a video will be shown to demonstrate the successful application of these in HWIL and Trials proving.

The need for high resolution complex infrared scene simulation has risen out of the growing use of IR sensor systems for imaging, detection, tracking, and guidance applications. The performance of an IR sensor system is highly dependent on the infrared environment in which the system is operating which can involve a wide variety of complex threats, background environments, and atmospheric conditions. The development, integration, and testing of infrared sensor systems, such FLIR, IRST, or Missile Warning Systems, requires an IR scene simulation capability that can provide complex scenes, in real-time, to ensure effective evaluation of system performance. To address this need, a Real-time Infrared Scene Simulator (RISS) was developed. The RISS system generates digital infrared scenes in real-time to provide a realistic portrayal of the infrared scene radiance as viewed by an IR system under test in threat engagement scenarios. Scene radiance is calculated on a frame by frame basis accounting for the relevant contributions from the sky, sun, targets, terrain, and atmosphere as a function of the engagement geometry. The following paper will provide an overview of the RISS system and discuss the critical issues that apply to real-time infrared scene simulation.

Hardware-in-the-loop (HWIL) simulation combines functional hardware with digital models. This technique has proven useful for test and evaluation of guided missile seekers. In a nominal configuration, the seeker is stimulated by synthetic image data. Seeker outputs are passed to a simulation control computer that simulates guidance, navigation, control, and airframe response of the missile. The seeker can be stimulated either by a projector or by direct signal injection (DSI). Despite recent advancements in scene projection technology, there are practical limits to the scenes produced by a scene projector. Thus, the test method of choice is often DSI. This paper discusses DSI techniques for HWIL. In this mode, sensor hardware is not used; scene signature data, provided directly to the seeker signal processor, is computed and sensor measurement effects are simulated. The computed images include sensor effects such as blurring, sampling, detector response characteristics, and noise. This paper discusses DSI methods for HWIL, with specific applications at the Air Force Kinetic Kill Vehicle Hardware-in-the-loop Simulator facility.

Real-time image visualization simulation for sensors operating against synthetic environments comprised of natural backgrounds, cultural features, mobile objects, and dynamic weather is now a reality. A commercial software product is available which is capable of providing sensor image visualization for any spectral filter from the visible through the far infrared. The produce is called SensorVision^TM and is a module of a product called Vega^TM. It is built upon IRIS Performer^TM and OpenGL^TM software and is targeted for use on Silicon Graphics Onyx^TM computers with InfiniteReality^TM or RealityEngine2^TM graphics hardware. Vega with SensorVision is ideally suited to provide the scene image input to a real-time hardware-in-the-loop sensor simulation ranging from image intensified night vision goggles, to midwave FLIRs, to longwave FLIRs. SensorVision images are quantitative (each image pixel is expressed in watts/cm²/steradian), are computed in real-time, and represent the diurnal effects of weather (including surface temperature variation) on scene images. This paper presents the radiometric processes and algorithms used by the software when computing its output images and discusses the use of the software in hardware-in-the-loop simulation. The paper also highlights software capabilities and features, e.g.: Images include reflection from sun/moon and ambient sky illumination, and thermal emission from extended polygons with radiometric shading between vertices, and atmospheric attenuation and path radiance with pixel line- of-sight variability; Polygon surface temperatures of natural backgrounds and cultural features are computed asynchronously and continuously updated throughout diurnal cycle; Polygons are radiometrically textured and spatially correlated with visible RGB textures.

The generation of high-fidelity imagery of infrared radiation from missile and aircraft exhaust plumes is a CPU intensive task. These calculations must include details associated with the generation of the plume flowfield and transport of emitted, scattered, and absorbed radiation. Additionally, spatial and temporal features such as mach discs, intrinsic cores, and shear layers must be consistently resolved regardless of plume orientation to eliminate nonphysical artifacts. This paper presents computational techniques to compute plume infrared radiation imagery for high frame rate applications at the Kinetic Kill Vehicle Hardware-in-the-loop Simulator facility located at Eglin AFB. Details concerning the underlying phenomenologies are also presented to provide an understanding of the computational rationale. Finally, several example calculations are presented to illustrate the level of fidelity that can be achieved using these methods.

Seascape is a distributed application that renders synthetic images using raytracing paradigm. It incorporates a computational model of infrared marine clutter. First principle models of water waves and light transport provide a computationally intensive clutter model implemented as a raytracer. Seascape models include sea, sky, and solar radiance, reflectance, attenuating atmospheres, constructive solid geometry targets, sensor, target, and water wave dynamics, and simple sensor image formation. Our focus is on the 3 - 5 micrometers waveband but Seascape can easily be configured for operation in the visible and longwave infrared. We have implemented an efficient parallel computation of this model on a heterogeneous array of UNIX workstations.

Real-time HWIL IR modeling requires special techniques to achieve the frame rates necessary for missile stimulation. Current methods depend heavily upon texture mapping to allow lower facet count target geometry models to be used. This paper describes the techniques for creating the signature models necessary for IR texture map generation. The primary IR signature modeling technique used at MICOM over the last few years is known as empirical modeling or target painting. This manual method directly applies 2D calibrated thermal imagery to a target geometry model. This method has the advantage of easy validation as the model is simply a 3D representation of measured data. The main disadvantages of the method is the finite amount of IR signature data and the high cost of collecting additional data. To address these issues, new techniques for creating PRISM models have been developed. The new method uses polygonal surface models and does not require BRL-CAD solid geometry models. This is desirable as there is a much larger vehicle model database available in, or translatable to, polygonal format. The IR signature models are based directly on calibrated thermal imagery collected under a variety of operating states, locations, and meteorological conditions. Hence, there is a high degree of confidence in these models as compared to purely predictive models as they are based directly on measurements.

Physics-Based Distributed Simulation using Optimistic Computing makes innovative use of emerging technologies to achieve faster generation of complex, multi-component physics-based information. The computational results are used in performing simulations that probe engineering issues relevant to system acquisition and in high-fidelity real- time distributed simulations. Four synergistic technologies are being brought together to bare on the question of high- fidelity scene generation to support HWIL simulation: integrating architectures for state-of-science, physics- based phenomenology models; protocols to support heterogeneous computers operating on a single network; accessible high-capacity networks; and optimistic synchronization to achieve demanding computational speed requirements and to overcome latency problems in real-time systems. We wish to report the first results from a multi- layer demonstration project that the Naval Research Laboratory has undertaken for the Ballistic Missile Defense Organization. We have made progress using the first three technologies and are planning to address optimistic synchronization in the near-future.

The Kinetic-kill-vehicle Hardware-in-the-Loop Simulation Facility (KHILS), located at Eglin AFB FL, has been involved in the development and ground testing of Ballistic Missile Defense Organization hit-to-kill interceptor concepts for 10 years. Work is ongoing to characterize the implement hardware-in-the-loop models for missile `environment' effects that are associated with high speed flight in general and endo-atmospheric flight in particular. Two critical areas of interest in endo-atmospheric simulation are: (1) effects on the line-of-sight due to divert thruster firings and the resulting structural vibration, and (2) the line-of-sight aero-optical environment which can be influenced by heated missile flowfields, coolant layers, and thruster fringes. The structural and aero-optical effects manifest themselves as image jitter, blurring, boresight shifts, and increased background radiance. At the KHILS facility, real-time closed-loop simulation techniques are being developed for structural and aero-optical effects presentation. These techniques include both software and hardware solutions. This paper describe the status of activities by describing the issues and the present KHILS solutions. The paper includes discussion of model interfaces with hardware-in-the-loop simulations, timing issues, and data transmittal bandwidth requirements. Image show the effects of structural and aero-optical disturbances on seeker focal plane energy distributions.

This paper describes recent technology development at Arnold Engineering Development Center to provide real-time closed- loop optical diagnostics for focal-plane-array and electro- optical sensor characterization and evaluation. Laser-based Direct-Write Scene Generation methods are used to simulate dynamic sensor operation and complex infrared backgrounds and target scenes. in order to provide more optimized optical simulation fidelity and to reduce computational burdens, closed-loop Direct Write Scene Generation image- synthesis methods employ image-to-object Whittaker-Shannon sampling, anisoplanatic optical convolution by quasi- isoplanatic spatial decomposition, and high-speed digital electronics for acousto-optic modulation. Optical and computational decomposition not only provide high-fidelity optical simulation for anisoplanatic optical sensors and complex infrared scenes, but also facilitates high-speed parallel-processing schemes for real-time closed-loop sensor operation. Some emphasis is devoted in this paper to describing the methodology and discussing fidelity and performance issues for closed-loop testing.

W-band monopulse stepped-frequency turntable measurements are reported. Data collection site, instrumentation, and test methodology are described in detail. The turntable measurements are used to generate point scatterer target models for all-digital and real-time HWIL simulations. Model development techniques are described. The models are validated against measurement data utilizing generic high range resolution acquisition and tracking algorithms. Validation methods and results are presented. Polarimetric signatures and modeling results for two ZIL-131 trucks measured in different configurations are compared. One truck has a canvas-covered bed, and the other, a command post vehicle, has a metal-covered plywood box structure on the back. Model implementation in assessment of seeker acquisition algorithms will determine capability to reject the trucks as low-value targets.

The advent of missile seekers with dual-mode millimeter wave and infrared common-aperture sensors has led to a requirement to develop the simulation tools necessary to test these systems. Traditionally, one of the most important techniques for supporting systems development has been a full seeker hardware-in-the-loop simulation. The development of simulation facilities capable of supporting the new generation of advanced dual-mode guided systems has been limited due to some major technological challenges which are yet to be solved. This paper provides an overview of the development of such a simulation facility at the U.S. Army Missile Command for supporting hardware-in-the-loop simulations of dual-mode systems. The major technological challenges which limit common-aperture dual-mode simulator development are presented with the current approaches which are being taken to overcome these challenges.

Several next-generation air defense missiles will use dual- mode guidance systems that simultaneously employ RF and IR sensors to obtain significant improvements in guidance performance. These missiles will require sophisticated hardware-in-the-loop test facilities to provide controlled signal environments to each sensor. Such test facilities allow accurate characterization of RF and IR sensors as well as the development and validation of guidance algorithms. Two approaches for dual-mode hardware-in-the-loop testing used at The Johns Hopkins University Applied Physics Laboratory (APL) are `electrically connected' and `collocated.' Each uses a common central computer to precisely coordinate RF and IR environment generators. The electrically connected approach requires disassembly of the guidance section and locating RF and IR seekers in different rooms. Extended electrical interfaces couple the seekers to the missile's guidance computer. This arrangement is well suited for development testing where flexibility is the primary concern. In the collocated configuration, disassembly of the guidance system is not needed since the RF and IR test environment generators are built into a common facility. This noninvasive configuration is useful in identifying and resolving performance issues associated with an integrated guidance system. This paper describes the capabilities and status of the collocated dual-mode Guidance System Evaluation Laboratory developed at APL.

As missile systems are becoming more complex and the costs associated with live fire testing are continuing to grow, greater emphasis is being placed on thorough system testing and capability evaluation in the simulation laboratories. To fully test these advanced missile guidance systems the simulation test facilities must present realistic, in-band backgrounds, targets, and countermeasures to the system being tested. This paper describes one aspect of an ongoing tri-service developmental program, Multi-Spectral Scene Generation (MSSG). MSSG is the combination of the RF and the IR energies for presentation to the unit under test for simultaneous RF/IR testing. The base material for the beam combiner must pass the RF radiation with minimal effect on amplitude and phase. The beam combiner must also reflect the IR radiation with minimal effect on the intensity and angular position of the test signals. The beam combiner may have to be moved during the testing. In this case the structure be capable of withstanding mechanical and aerodynamic loading without corrupting the RF and IR signals. The blending of the IR and RF signals must be accomplished without corrupting either signal to the point where test artifacts are created by the test process or the test facility.

The Millimeter/Infrared (MMIR) Simulation System, completed in June 1991, was developed primarily to perform Hardware- In-The-Loop (HWIL) evaluation of Sensor Fused Munitions (SFMs), including the Sense and Destroy Armor submunition. Due to the nature of SFMs, the MMIR includes several unique design features. This paper describes design of the MMIR Simulation System, including the design tradeoff decisions that were made in order to optimize the effectiveness of HWIL evaluation for this family of multi-spectral weapon systems.

Hardware-in-the-Loop (HWIL) simulation is an effective, low cost alternative to flight testing for performance evaluation and development of guided missile RF seekers. Accurate generation of a simulated RF environment including target and clutter return is of primary importance in creating a realistic HWIL simulation. This paper discusses the signal generation requirements for typical millimeter- wave seeker simulation and the hardware developed for their implementation. Special emphasis is placed on a device for computer-controlled I/Q modulation called a Digital Quadrature Modulator.

In this paper, a concept of Avionics Simulator is described. This simulator consists of six subsystems, which are a large scale flight table (LFT), a small but high precision flight table (HFT), a target simulator (TS), a central processing system (CPS), a central console (CC) an a large anechoic chamber. The LFT physically simulates an own-ship motion (roll-pitch yaw) and a Fire Control Radar (FCR) and an Inertia Reference System (IRS) are installed into the inner roll gimbal of the LFT. The HFT is used for test and evaluation of the IRS. The TS consists of a billboard array antenna and a target generator. This TS can simultaneously generate two targets under the sea clutter or the ground clutter and radiate RF target-echo signals from the billboard array antenna to the FCR. The CC can realtimely simulate a relative motion (6-degree-of-freedom) between own-ship and multi-targets and transfer an own-ship motion command to the LFT and also each relative range and velocity command to the target generator. The CC consists of an operational console, target and outer scene image generator and a projection screen (100 inches). Avionics Simulator can do Hardware-in-the-Loop Testing of the FCR and the IRS under synthetic environments preceding actual in-flight testing.

The KHILS facility in the Wright Laboratory Armament Directorate at Eglin AFB has developed a hardware-in-the- loop (HWIL) simulation for the Low Cost Autonomous Attack System. Unique techniques have been developed for real-time closed-loop signal injection testing of this Laser Radar (LADAR) guided munition concept. The overall HWIL layout will be described including discussion of interfaces, real- time 3D LADAR scene generation, flight motion simulation, and real-time graphical visualization. In addition, the practical application of a new simulation Verification, Validation and Accreditation procedure will be described in relation to this HWIL simulation.

A Missile Warning Receiver Integrated Support Station (MWR- ISS) was designed to perform missile engagement scenario testing with the AN/AAR-44 Missile Warning Receiver (MWR). The MWR-ISS employs the Real-Time Infrared Scene Simulator coupled with a real-time AN/AAR-44 sensor emulation to provide direct signal injection to the AN/AAR-44 Signal Processing Unit. Three sets of tests were performed to demonstrate the radiometric validity of the MWR-ISS. The first test demonstrated the accuracy of the sensor emulator through a comparison of measured laboratory collimator data with simulated data. The second test demonstrated correlation between live missile firings as observed by the AN/AAR-44 at White Sands Missile Range and simulation of the fringes using the MWR-ISS system. The third test demonstrated correlation between live missile firings as observed by the AN/AAR-44 at the Holloman Sled Track and simulation of the firings using the MWR-ISS system.

This paper illustrates how risk for the Navy Lightweight Exo-Atmospheric Projectile (LEAP) Technology Demonstration program was reduced using hardware-in-the-loop (HWIL) testing of the GPS/INS function in JHU/APL's Navigation and Guidance System Integration Laboratory (NAVSIL) facility. Under LEAP, a new STANDARD Missile based interceptor and a shipboard weapon system was built to demonstrate the potential of integrating the required technologies to defend against tactical ballistic missiles in outerspace (prior to atmospheric reentry). The LEAP system used an integrated GPS/INS package to provide accurate knowledge of interceptor attitude as well as position and velocity, which were critical to pointing the Kinetic Kill Vehicle at the target. The mission contained both high acceleration and high velocity while demanding high accuracy attitude estimates at the end of the short flight. The NAVSIL facility provided a high-fidelity HWIL approach to testing missile guidance systems that utilize GPS/INS guidance. Precise control and repeatability were provided for the two primary sensor inputs: GPS RF and the inertial measurements with instrument errors. HWIL tests were driven by high-fidelity all-digital 6-DOF missile motion simulations that accurately generated the translational and attitude dynamics in all phases of the mission from pre-launch through to the target. Real-time antenna pattern simulation was implemented to assess impact of signal level effects on GPS receiver performance. An innovative real-time technique was employed to simulate the frequency shift induced in the GPS receiver oscillator due to high-g forces, thus allowing accurate laboratory assessment of the receiver's ability to track, reacquire,a nd accurately navigate under g load. The resulting responsive high-fidelity HWIL testing capability provided critical support to development of the GPS/INS package and an independent assessment of expected GPS/INS performance during the mission.

The CRC Hera targets program integrates Government Furnished Equipment, that includes Pershing II flight computers and Minuteman boosters, to provide threat representative targets to the U.S. Government in support of theater missile defense interceptor test programs. Hardware-in-the-Loop (HWIL) and Computer-in-the-Loop (CIL) testing is used, from initial software development through system and software qualification, to evaluate Hera target vehicle performance. The CIL and HWIL closed loop test methods differ not only in the amount of hardware needed for the test but also in the level of system validation. CIL flights using only a real- time simulation computer and a flight computer to create a closed loop test environment for the airborne software. We use this method for the development, validation and certification of the flight software. HWIL flight testing employs both actual missile flight computers and inert booster motors with actuators. The flight computer, actuator controller, and two reaction control systems from the actual flight missile are connected to lab shop queen equipment. This equipment includes first and second stage motor nozzle actuators, battery and ordnance simulators, raceway cables and the telemetry system. The HWIL test not only verifies proper airborne software operation but also verifies the flight computer interfaces with raceway cabling and the missile subsystems. The HWIL test demonstrates the flight readiness of the airborne software and several key pieces of flight hardware. Both nominal and stacked tolerance simulation runs are used to validate the flight code and to provide stressful conditions to verify the robustness of the flight control system. Monte Carlo runsets using known CIL/HWIL interface errors, such as scale factor, bias and noise, are used to create minimum-maximum boundary value plots. These boundary value plots provide guidelines to verify and validate the airborne software tested by the CIL/HWIL simulated flights. Comparisons of flight data from three of our test flights and corresponding CIL/HWIL runs show an excellent match of flight performance to pre-flight predictions. The CIL/HWIL testing on the HERA targets program made it possible to have a high degree of confidence in the flight software and hardware before our first mission. We achieved first flight success due in part to the extensive software and hardware testing in the CIL/HWIL environment from software development through system qualification.

The purpose of having dynamically adaptive load stand capability is to verify and monitor control section actuator performance under simulated free-flight aerodynamic load conditions in a Closed Loop Real Time HWIL environment. HWIL testing is a cost effective and risk reducing means of evaluating missile system prior to flight testing. This article develops methods of designing, analyzing, and testing of an extension spring driven load stand. Load stand spring natural and surging frequencies are evaluated. Nonlinear control section actuator anomalies are discussed in terms of load stand testing. Actuator time response data is examined under hinge moment and normal force loaded conditions. A design verification procedure was executed to provide a high degree of assurance that the load stand would perform as predicted by analytical methods.

Real-time hardware-in-the-loop simulation of a spaced based kinetic kill vehicle (KV) is described. Simulation models are executed in real-time on an EAI SIMSTAR computer. Models include high fidelity KV kinematics and dynamics, thruster actuators, mass properties, and a high velocity exoatmospheric target. A Carco Flight Motion Simulator is used to exercise the test hardware inertial measurement unit and IR sensor. A Lockheed Martin PT-2000 Computer Image GEnerator is used to produce target and background imagery to the sensor. IR scene projection is produced by an Aura Systems Infrared Scene Projector. Hardware interfacing is facilitated via the use of VME based systems.

A steerable laser infrared projector (SLP) has been designed by Aegis Research Corporation and is currently being integrated into the Kinetic Kill Vehicle Hardware-in-the- Loop Simulator facility located at the Wright Laboratory Armament Directorate, Eglin Air Force Base, FL. The SLP utilizes lead salt laser diodes as the projector sources and two-axis galvanometer beam scanners to project six independently controlled point source targets to the unit- under-test. The laser diodes provide high intensity, 16 BIT radiometric resolution targets while the galvanometers provide wide angle, high precision (16 BIT) beam steering performance. Due to the nonlinear relationship between the input drive current and the output power of the diodes the calibration of the multiple sources is critical to the successful utilization of the projector.

Efforts to produce a fiber optic based high spatial resolution (4 X 10⁶ pixels/in²) infrared (IR) scene projector for background scene applications are described. Light from a source scene is transmitted by total internal reflection to thin film optical black body cavities at the ends of the fiber elements and converted to IR radiation. The design of the optical thin film black body cavity allows flexibility to tune both source and output characteristics for the scene projector and tailor in-band emissivities to values greater than 0.9. Fiber elements are micromachined into the optic to provide thermal isolation between scene pixels and minimize thermal cross talk. The materials and processes being investigated are discussed with respect to thermal modeling results which direct design considerations. Examples of IR images produced by this approach are presented with discussions of future plans.

The KVACC is a part of the Air Force Kinetic-kill vehicle Hardware-In-the-Loop Simulator facility whose purpose is to enable IR scene projection with a below ambient `cold' background for increased dynamic range and closer simulation realism. The geometric and spectral description of the system will be presented in the paper along with discussion as to operational details including cleanliness requirements, vacuum pump down time, and chill down rates using LN₂. In addition, the lessons learned from integration checkout using a 512 X 512 Cryogenic Resistor array Infrared Scene Projector will be annotated. Upgrade potential and future plans, including Helium refrigerators will also be detailed.

Real-time closed loop simulation of LADAR seekers in a hardware-in-the-loop facility can reduce program risk and cost. This paper discusses an implementation of real-time range imagery generated in a synthetic environment at the Kinetic Kill Vehicle Hardware-in-the Loop facility at Eglin AFB, for the stimulation of LADAR seekers and algorithms. The computer hardware platform used was a Silicon Graphics Incorporated Onyx Reality Engine. This computer contains graphics hardware, and is optimized for generating visible or infrared imagery in real-time. A by-produce of the rendering process, in the form of a depth buffer, is generated from all objects in view during its rendering process. The depth buffer is an array of integer values that contributes to the proper rendering of overlapping objects and can be converted to range values using a mathematical formula. This paper presents an optimized software approach to the generation of the scenes, calculation of the range values, and outputting the range data for a LADAR seeker.

An End-To-End Simulation capability for software development and validation of missile flight software on the actual embedded computer has been developed utilizing a 486 PC, i860 DSP coprocessor, embedded flight computer and custom dual port memory interface hardware. This system allows real-time interrupt driven embedded flight software development and checkout. The flight software runs in a Sandia Digital Airborne Computer and reads and writes actual hardware sensor locations in which Inertial Measurement Unit data resides. The simulator provides six degree of freedom real-time dynamic simulation, accurate real-time discrete sensor data and acts on commands and discretes from the flight computer. This system was utilized in the development and validation of the successful premier flight of the Digital Miniature Attitude Reference System in January of 1995 at the White Sands Missile Range on a two stage attitude controlled sounding rocket.

Servo systems play an important role in many automated processes. In order to fulfill the hard demands on reliability and fast and precise operation, intelligent concepts for the control, supervision and (re)configuration are necessary. In this paper, an approach is presented which integrates different levels of signal processing in an electromechanical servo system. The digital controller and the model-based fault detection scheme are designed taking into account model-uncertainty and the time variant process behavior, which is caused by temperature influences, wear, aging, etc. After a brief description of the theoretical basis an experimental application shows results for an automobile servo system which is driven by a d.c. motor.