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For performance modelling of optical countermeasure systems simulation of turbulence effects is necessary. Physical optics numerical beam propagation using phase screens is an established method in this respect. In some cases a short sequence of temporally resolved phase screens is available from Computational Fluid Dynamics (CFD) simulations or from wavefront sensor measurements. It is, however, seldom possible to provide enough sequences and sufficient sequence length for Monte Carlo simulations of system performance utilizing these methods. Therefore, we have investigated the possibility to generate an arbitrary number of longer temporal sequences of phase screens with the same statistical properties for simulation of turbulence, based on an available short phase screen sequence. The method apply Proper Orthogonal Decomposition (POD), a method used to generate orthogonal modes from a dataset. For discretely sampled sequences the Singular Value Decomposition (SVD) algorithm is suitable to extract the set of POD modes. This scheme provides a separate temporal sequence of coefficients for each spatial mode. The next step is to generate new, longer temporal sequences of coefficients with the same statistical properties as those extracted by the SVD algorithm. Finally a new sequence of phase screens is generated by adding all spatial modes. The method is illustrated using data from CFD calculations of a down-scaled jet engine plume. The method is especially suitable for very strong localized turbulence as in aero optics and engine exhaust plumes, but may be useful also for extended turbulence. The use to generate Power-In-Bucket (PIB) sequences for evaluation of turbulence distortion effects is demonstrated. PIB is an important quantity when evaluating e.g. the performance of directed infrared countermeasure (DIRCM) systems.

The James Webb Space Telescope cryogenic testing requires measurement systems that both obtain a very high degree of accuracy and can function in that environment. Close-range photogrammetry was identified as meeting those criteria. Testing the capability of a close-range photogrammetric system prior to its existence is a challenging problem. Computer simulation was chosen over building a scaled mock-up to allow for increased flexibility in testing various configurations. Extensive validation work was done to ensure that the actual as-built system meet accuracy and repeatability requirements. The simulated image data predicted the uncertainty in measurement to be within specification and this prediction was borne out experimentally. Uncertainty at all levels was verified experimentally to be less than 0.1 millimeters.

Existed simulation works always emphasize on procedural verification, which put too much focus on the simulation models instead of simulation itself. As a result, researches on improving simulation accuracy are always limited in individual aspects. As accuracy is the key in simulation credibility assessment and fidelity study, it is important to give an all-round discussion of the accuracy of distributed simulation systems themselves. First, the major elements of distributed simulation systems are summarized, which can be used as the specific basis of definition, classification and description of accuracy of distributed simulation systems. In Part 2, the framework of accuracy of distributed simulation systems is presented in a comprehensive way, which makes it more sensible to analyze and assess the uncertainty of distributed simulation systems. The concept of accuracy of distributed simulation systems is divided into 4 other factors and analyzed respectively further more in Part 3. In Part 4, based on the formalized description of framework of accuracy analysis in distributed simulation systems, the practical approach are put forward, which can be applied to study unexpected or inaccurate simulation results. Following this, a real distributed simulation system based on HLA is taken as an example to verify the usefulness of the approach proposed. The results show that the method works well and is applicable in accuracy analysis of distributed simulation systems.

Computer models have been developed and used to predict the performance of vehicles equipped with advanced fuel and power train technologies such as hybrid electric or fuel cells. However, simulations that describe the interaction of the vehicle with the rest of the vehicle fleet and infrastructure are just emerging. This paper documents the results of an experiment to demonstrate the utility of these types of simulations. The experiment examined the business case of fielding hybrid electric, high-mobility multipurpose wheeled vehicles (HE HMMWVs) in a future Army organization. The hypothesis was that fielding HE vehicles would significantly reduce fuel consumption due to the economy offered by the HE technology and reducing the number of generators as a result of using the vehicles to generate electrical power. The Logistical and Combat Systems Simulation (LOCSS) was used to estimate differences in fuel consumption and associated equipment during a 72-hour operation with and without HE HMMWVs. There was a 25 percent reduction in fuel consumption over the systems examined. However, due to the relatively low density of the HE vehicles in the organization, the total difference in fuel consumption was not operationally significant; and the savings in fuel costs did not overcome the additional procurement costs over a twenty-year life cycle.

This paper will present the results and progress of AMRDEC'S development of two cold background, flight motion simulator (FMS) mountable, emitter array based infared scene projectors for use in hardware-in-the-loop systems simulation. The goal for this development is the ability to simulate realistic low temperature backgrounds for windowed/domed seekers operating in tactical and exo-atmospheric simulations. Two projectors have been simultaneously developed; the first represents a streamlined pathfinder version consisting of a Honeywell emitter array and refractive optical system contained within an FMS-mountable environmental chamber cooled to -55 degrees Celsius. The second system is the full-capability version including a cryogenically operated BRITE II emitter array, zoom optics, integrated steerable point source and high-frequency jitter mirror contained within a similar FMS-mountable environmental chamber. This system provides a full-FOV cold background, two dimensional dynamic IR scene projection, a high dynamic range independently steerable point source and combined optical path high frequency jitter control. Both projectors are designed to be compatible with operation on a 5 axis electric motor driven Carco flight motion simulator. Results presented will include design specifications, optical performance, samlple imagery, apparent temperature and proposed future improvements.

The development of large, complex systems, the training of personnel, and the refinement of concepts of operations all depend on high-performance simulation technologies. For each of the above application areas, among others, there is a chronic need for ever-higher performance. This paper addresses the application of three simulation acceleration approaches, used independently or in conjunction with one another: parallel simulation, mixed-abstraction/multiresolution simulation, and hardware acceleration via reconfigurable computing elements. After discussing the merits of each approach, the paper presents analytic techniques for determining the most effective approach to use for a given simulation problem.

While the military and commercial communities are increasingly reliant on simulation to reduce cost, the cost of developing simulations for their complex system may be costly in themselves. In order to reduce simulation costs, simulation developers have turned toward using collaborative simulation, reusing existing simulation models, and utilizing model abstraction techniques to reduce simulation development time as well as simulation execution time. This paper focuses on model abstraction techniques that can be applied to reduce simulation execution and development time and the effects those techniques have on simulation accuracy.

Significant advances are being made in the application of Modeling and Simulation (M&S) technologies to support Government initiatives for Simulation Based Acquisition (SBA) and Simulation, Test and Evaluation Process (STEP) in the Army transformation. This paper describes a collaborative approach to Family of Systems (FoS) M&S in use on the FOSSIM program to evaluate critical Theater Air and Missile Defense (TAMD) integration and interoperability issues and to explore opportunities for advanced technology exploitation. This paper provides an overview of the FOSSIM concept and describes the collaborative development and utilization methodology. Key topics discussed include Systems Engineering and Design, Model Engineering and Development, Systems Analysis, and Configuration Management (CM). The paper concludes by summarizing the FOSSIM simulation environment and modeling capabilities.

The Virtual Targets Center (VTC) is a strategic alliance between the Targets Management Office within the US Army Simulation, Training, and Instrumentation Command (STRICOM) and the Systems Simulation and Development Directorate within the US Army Aviation and Missile Command (AMCOM). This center reduces duplication of effort by making DoD owned geometry models available for reutilization and supports the modeling and simulation community by redistributing or creating geometry models in formats applicable to a wide range of simulation activities. In addition to these activites, the VTC is developing methods and tools to enhance existing target models. A new software simulation exists at the VTC to automatically create facet models of camouflage netting by considering the netting as a 2D membrane that balances internal tensional stresses and the external force of gravity by assuming a minimum energy configuration - accurately replicating the draping of real netting. The geometric information of this virtual camouflage netting is exported to a file in a format commonly used for three-dimensional modeling, thereby making it available to workers in signature prediction and visualization.

AEROSPATIALE MATRA MISSILES has been involved in sensors, scenes and systems simulation for more than 10 years. These simulations are mainly used for missile guidance or target detection and tracking. They have been improved continuously and have become more and more realistic. They are now essential tools for the development and qualification of complex systems. This paper presents the evolutions of simulations through different examples (air-to-ground missile with IR terminal guidance and optronic firing post).

The Virtual Targets Center is a strategic alliance between STRICOM's Targets Management Office and AMCOM's Systems Simulation and Development Directorate. The Virtual Target Center reduces duplication of effort by making DoD owned geometry models available for reutilization. The mission of the Virtual Targets Center is to support the modeling and simulation community by collecting, creating and distributing geometry models in multiple formats applicable to a wide range of simulation activities. The Virtual Targets Center hosts The Virtual Targets Archive on a secure web site that is available to all DoD agencies and their contractors. The Archive allows a member to easily locate a model and determine its relevance to a desired application. Once a required model has been located, the member may download the model immediately. The geometry models maintained in the Archive are collected from various sources in the modeling and simulation community. The Archive includes target geometry models of resolutions ranging from high facet count predictive radar models to low facet count, real-time visualization models. Also included in the Archive are both empirical and predictive infrared signature models. The Virtual Targets Center provides support in modeling radar and infrared signatures of targets, and use of geometry models in simulations. The Virtual Targets Center makes DoD owned geometry models easily accessible to the modeling and simulation community.

For the past three years, the U.S. Army Aviation and Missile Command has been developing a hardware-in-the-loop (HWIL) simulation facility to test common aperture multi-spectral missile seekers. This paper discusses the problems encountered during the development of this facility, the solutions, and the resulting capability of this unique HWIL simulation facility. The Advanced Simulation Center is managed and operated by the Systems Simulation and Development Directorate of the Missile Research, Development, and Engineering Center, Redstone Arsenal, Alabama.

The advent of missile seekers with dual-mode millimeter wave and infrared common-aperture sensors has led to a requirement to develop 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. For the past three years, U.S. Army Aviation and Missile Command (AMCOM) has been developing the simulation technologies to test these types of system in a hardware-in-the-loop environment. The dichroic beam combiner is the key component of such a facility. This paper focuses on the various dichroic beam combiner technologies that have been considered and are currently under development at AMCOM. This paper will present both experimental and analytical data to describe the performance of each technology. The basis for this paper is work performed at the AMCOM Advanced Simulation Center (ASC). The ASC is managed and operated by the Systems Simulation and Development Directorate of the Missile Research, Development, and Engineering Center, Redstone Arsenal, Alabama.

Simulation of large complex systems for the purpose of evaluating performance and exploring alternatives is a computationally slow process, currently still out of the domain of real-time applications. This paper overviews advances in three directions aimed at overcoming this limitation. First, based on developments in the theory of discrete event systems, concurrent simulation enables the extraction of information from a single simulation that would otherwise require multiple repeated simulations. This effectively provides simulation speedups of possibly orders of magnitude. A second direction attempts to use simulation for the purpose of obtaining a 'metamodel' of the actual system, i.e., an approximate 'surrogate' model which is computationally very fast, yet accurate. We specifically discuss the use of neural networks as metamodeling devices which may be trained through simulation. Finally, hierarchical simulation provides yet another means for speedup, a major challenge being the preservation of fidelity between hierarchical levels. In practice, using the statistical average of a high resolution level simulator output as the input for a lower resolution level causes significant loss of stochastic fidelity. We present an approach in which we cluster the high resolution simulation output into 'path bundles' as the input for the lower resolution level. The paper includes applications of these new directions to areas such as combat simulation and design of C3I systems.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A first phase demonstration of the capabilities and limitations of an optical correlator in a realistic environment has been completed. The testing was divided into several areas, from laboratory data gathering to a fully functional helicopter-delivered demonstration airframe. The basic research performed has led to three fully fieldable test units which have proven to be rugged and dependable under normal test range conditions. The units were transportable and required no realignment of the optics. Two of the test systems were modular in construction while the third was a 'solid optic' design having optical paths and components contained within a solid glass construction. Two flights have been completed so far, and in both cases the target was identified and tracked, and an airframe guided to target impact.

A description of the simulation model and the on-ground performances validation of the Acquisition and Tracking (PAT) subsystem and of the European SILEX program is presented. The SILEX scenario is composed of two terminals mounted on LEO orbit (SPOT 4) and geostationary orbit (ARTEMIS) spacecrafts. The PAT subsystem is in charge of the initialization of the link, of the tracking of the incoming beam and of the pointing of the emitted laser beam. A short description of the retained strategies (phases of the PAT mission and operating modes) and functional architecture (control laws and sampling frequencies) is presented. In order to validate the PAT performance assessment, a complete simulation software is developed. The model (equipment modeling, dynamical simulation of the terminal structure, and operating modes management) and the associated outputs are examined in detail. The chosen design and architecture of the PAT validation on a system testbed (STB) are described. The validation of a pointing system for optical intersatellite communication, thanks to the combination of simulations and STB measurements, is shown.

There is a need to calibrate satellite data obtained at large polar (i.e. off-nadir) view angles for effects caused by scanner geometry and by the atmosphere. If such effects are not corrected for, then recorded radiance data will contain systematic and random errors which will make accurate target identification and quantification difficult. Adequate calibration of digital radiance data requires both an inductive analysis of digital satellite images and a deductive analysis based upon a priori simulation studies. The inputs to a simulation model (ground reflectance, atmospheric transmission and bandscatter) and their variability are dependent upon (for example) sun-target-sensor geometry. There is a major need to make accurate ground reflectance measurements to provide calibration information on the anisotropy of ground reflectance. There is also a need to assess atmospheric transmission and backscatter from the image itself. A potential simple, inexpensive method for making ground reflectance measurements in the above context is discussed.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The use of laser systems for space-based communication applications has drawn considerable attention recently. It is anticipated that laser communication satellites will become a reality in the mid to late 1980s. The fine pointing and jitter control requirements of those systems presents some unprecedented challenges to control engineers in the areas of acquisition, tracking, and fine pointing. This paper addresses the various acquisition methods and critical technological issues of tracking and pointing control for space-based laser communication system applications under their dynamic operating environment and stringent mission requirements. The most stressing design and development parameters and components for various applications are discussed. The structure of a digital computer simulation program which can be utilized for performance verification, design feasibility, and sensitivity study, is also given.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Coherent optical processing can be effectively used to detect moving objects against a background of fixed objects and noise. If done digitally, the task can require a large amount of processing power. The optical approach is to do pattern recognition in the frequency plane of the time-integrated sky image. A spatial filter, matched to the spectral energy distribution of the moving objects, rotates in the frequency plane. Earlier experiments established the validity of the approach'. The processor has since been refined, simplified and implemented in an optical/digital configuration. A small digital computer (PDP 11/03) provides simulated input data, controls the operation of the optical processor, and displays the results.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A detailed discussion of statistical sensor performance analysis was presented in a previous SPIE publication. The essential point of the paper was to the effect that responsible sensor performance analysis in real world conditions required statistical formulations and techniques in order to obtain complete and unambiguous conclusions. In this earlier paper illustrations were presented of applications using this statistical approach. In addition, a method was developed for circumventing the difficulties inherent in Monte Carlo processes, customarily considered necessary for the statistical analyses of interest. It was mentioned in this previous work that further development of the foundations of the technique were in progress. The primary purpose of the present paper is to convey those elements of progress which have been achieved since the original work was presented.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A contractual study of Advanced On-Board Satellite Signal Processor technology (DARPA, USAF-RADC Contract F30602.78.C.0028) included, in part, evaluation of various processor architectures and integrated circuit components for use with military sensor systems, especially electro-optical and radar, for the era of the late 1980's. High level architectural tradeoff studies were performed in a novel application of the simulation language, ECSS/Simscript. Typical statistical results of the simulation are shown, illustrating how the data are used to measure throughput, to estimate prime power needs to discover contention in array processing, and to provide preliminary guidelines for allocation and proportioning of signal processor resources. Component studies indicated that a programmable high speed signal processor element containing logic, control, and local memory could be realized perhaps on a single VLSI chip. Array architectures evaluated by simulation were capable of satisfying a wide spectrum of mission requirements. Anticipated progress in military and commercial IC technology should provide a basic pro-cessing element adequate for all needs. The switching and management of data flow to and from bulk memory, which appears to be a very difficult software analysis problem, can be eased by guidelines derived from simulation.

This paper outlines a successful approach to the performance evaluation of competing concepts. Only space--looking systems are considered. No specific results are given; rather a general methodology is presented.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Various methods for simulation of reticle-systems will be described, which have practical application for the simulation of missile guidance systems. The reticle-pattern, as well as the received image, is digitized using common picture processing equipment. The sampled representations, of the reticle and image, are converted to a polar-coordinate system, and the data is then put into a vector-string. Setting up a cyclic matrix with this vector-string, one can describe the periodic system-signal by cyclic convolution of reticle-string and image-string. For this linear discrete system approximation, the transfer function in the Z-domain can be deduced. A similarity transform to the Jordan form of a quadratic cyclic matrix, by means of the discrete Fourier matrix, reduces the amount of calculations required. This is an advantage in digital simulation.

It was recognized that precision pointing provided by the Orbiter's attitude control system would not be good enough for Shuttle payload scientific experiments or certain Defense department payloads. The Annular Suspension Pointing System (ASPS) is being developed to satisfy these more exacting pointing requirements. The ASPS is a modular pointing system which consists of two principal parts, including an ASPS Gimbal System (AGS) which provides three conventional ball-bearing gimbals and an ASPS Vernier System (AVS) which magnetically isolates the payload. AGS performance requirements are discussed and an AGS system description is given. The overall AGS system consists of the mechanical hardware, sensors, electronics, and software. Attention is also given to system simulation and performance prediction, and support facilities.

A method to improve the locating accuracy of a multi-detector system was proposed. In order to appraise the method, the target, the corresponding irradiance distribution function and the whole process for information extraction were simulated by the computer. The result shows that in some circumstance the locating accuracy will be improved in a great deal.

Military radar systems require complex and adaptive signal processing to achieve optimum performance. In addition to this performance requirement is the need for high system reliability. A signal processing architecture that is modular and programmable has been a critical requirement for many years. The approach used to meet this requirement necessitates the use of identical VLSI/VHSIC components. The task of evaluating a design is normally accomplished by breadboarding. However, this can not be done until the IC's have been developed. An obvious alternative is to simulate the system at the register-transfer and or gate level. This method has been used in the past but is limited to system fragments due to the excessive storage and CPU time required. In order to validate advanced radar signal processor hardware, software, and firmware, a digital simulation tool has been developed which allows the system designer to evaluate alternatives with minimum effort, storage, and execution time. The top-down design procedure is utilized to guide the user from system requirements to final system design.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The user of any imaging system is primarily concerned with securing some desired level of perception performance against real world objects of interest under anticipated typical operating conditions. Develop­ ing validated predictive models for this T field1 performance involves a number of complexities and sources of uncertainty which are not encountered when modelling hardware performance from objective laboratory measurements.These problems become apparent in the course of describing the basis of a program for generating the perception probability versus range curve for intensifier sights and a statistical trial which was conducted to validate its predictions.IntroductionThe requirement for a predictive field performance model for image intensifier systems has only arisen relatively recently. This was partly a response to a greater sophistication in user specification of field performance, and partly because of the greater range of variants and alternatives available for those components affecting intensifier performance. Previously it had been possible to confidently predict the field performance of proposed new designs by extrapolating from direct field measurements using readily available systems based on the same types of component.This contrasts with the situation in thermal imaging, where the greater complexity and range of design variables of these systems and the difficulties in procuring them for evaluation made it necessary to develop performance measures and modelling techniques in parallel with the systems.Field performance modellingThe higher perceptual processes of recognition and identification are not so well defined as that of detection. Moreover, the underlying mechanisms and image quality requirements relating to the achievement of a specified level of performance are not yet understood in detail. Consequently field performance modelling in the present state of the art relies on empirically derived relationships.Analysis of a large and growing bank of trials data at the Night Vision Laboratories, Port Belvoir, U.S.A. l indicates that the perception probability, P, of military vehicle targets can be related to the number of spatial cycles, f, which could be discriminated.by an observer using the imager or* a bar target of equivalent size and mean modulus of stimulus signal with respect to the immediate background. Clearly, accommodating human observer variability and using this very simple characterisation for a variety of complex stimulus profiles necessarily implies a limited precision. This appears to be of the order of + 15% in f, which is acceptable for many situations.The empirical fit shown in Figure 1 which is valid over the operationally significant range of P is modelled by:(f)p -^ .dy (1)r-with:This P is a standard normal cumulative distribution in the transformed variable x. a has a value of 0.21 and the value of f (P= 0.5) takes values of 1.0 for detection in medium to low clutter, 3.5 for recognition and 7«0 for identification.