Within the military environment there is a growing interest in the use of synthetic imagery as a method for assessing the performance potential of many assets, such as camouflage systems, ATR/I systems, future sensor systems and the susceptibility of such systems to countermeasures. Field trials are expensive, subject to the vagaries of weather, and cannot be used to design or assess new systems and technologies. The requirements for high fidelity synthetic image simulation differ quite significantly dependent on the application area. The Camouflage Electro-Optic Simulation System (CAMEO-SIM) has been developed as a modular system to deliver 0.4-20 micron² 32-bit physics based synthetic imagery to defense researchers in the UK based on a 3D textured geometric representation of the synthetic environment. The system has been developed to be sufficiently flexible to support a wide range of defense applications requiring synthetic image streams as their inputs. The key difference between the CAMEO-SIM system and commercial image generation systems is that CAMEO-SIM is a first principle simulator working in spectral radiometric space solving the underlying physical equations of radiation transport. This difference underpins the military usefulness of the system and also enables the system to become predictive in nature. Using CAMEO-SIM, the user can examine the effects of changes in input parameters such as time of day, weather, material properties (optical and thermophysical), and wavelength from one set of geometric and textural information to assess the effects on the performance of the defense function being researched. If this goal can be achieved more robust defense function performance, due to larger available training sets or better understanding of the issues at the start of the development, will ensue. This paper outlines the development status of the CAMEO-SIM system and describes the current enhancements undertaken to improve the fidelity and accuracy of the system for more recent defense requirements. The paper also outlines the currently identified areas of development to provide improved capability. The paper also discusses the interaction between the CAMEO-SIM system and the Fidelity Investigation and Reporting Environment (FIRE) system. This enables the modeler to examine early in the modeling process the quality of the textural and geometric information used in the synthetic imagery.

When using synthetic imagery it is essential that it is fit for purpose. Imagery can be rendered at different levels of quality, depending on application. For example, when using a real-time system, rendering speed is a critical parameter but, when assessing the effectiveness of a camouflage system, physical accuracy is likely to be more important. A method to quantify the accuracy of the imagery, for particular applications, is necessary. A range of different metrics based on wavelets, higher order statistics, and a human vision model, has been developed to assess the fidelity of synthetic imagery. These metrics have been used to analyze synthetic imagery rendered at different levels of fidelity and to compare the synthetic imagery with real- world imagery. Some of the metrics can be used to compare two spatially correlated images, whereas others can be used to assess particular characteristics of the image such as clutter level. The metrics, and first order statistics, have been incorporated into a tool box called FIRE (Fidelity Investigations and Reporting Environment). This paper will describe the metrics used and the results of analyses undertaken.

CAMEO-SIM was developed as a laboratory method to assess the effectiveness of aircraft camouflage schemes. It is a physically accurate synthetic image generator, rendering in any waveband between 0.4 and 14 microns. Camouflage schemes are assessed by displaying imagery to observers under controlled laboratory conditions or by analyzing the digital image and calculating the contrast statistics between the target and background. Code verification has taken place during development. However, validation of CAMEO-SIM is essential to ensure that the imagery produced is suitable to be used for camouflage effectiveness assessment. Real world characteristics are inherently variable, so exact pixel to pixel correlation is unnecessary. For camouflage effectiveness assessment it is more important to be confident that the comparative effects of different schemes are correct, but prediction of detection ranges is also desirable. Several different tests have been undertaken to validate CAMEO-SIM for the purpose of assessing camouflage effectiveness. Simple scenes have been modeled and measured. Thermal and visual properties of the synthetic and real scenes have been compared. This paper describes the validation tests and discusses the suitability of CAMEO-SIM for camouflage assessment.

A compelling figure-of-merit for synthetic sensor data generation is target acquisition performance relative to field data of similar scenarios. That is, if one synthesized a sensor data set from the ground truth of an actual field measurement, one would expect a realistic simulation to give rise to probabilities of target detection and identification, and false alarm rates comparable to that of the field data. This correlation would, of course, be expected to extend to both human and machine-based performance. Key to this correlation is realistic background synthesis, providing appropriate spatial and spectral competition with the target signatures for both man and algorithm. Hyperspectral target signature synthesis is fairly mature, while background modeling for target- competitive clutter leaves much to be desired. The authors herein detail a ray-tracing approach for rigorous hyperspectral background signature synthesis that focuses on trees and forest canopies, and synthesis techniques for producing spatial-spectral statistics consistent with field data. In addition, the authors present some of the hyperspectral synthesis components, including the signature model, which can be used in a multi-spectral mode for real- time EO/IR image synthesis.

The acquisition a robust set of IR imagery is frequently impossible through the traditional image collection process. On the other hand, the use of a full-scale simulation is too time consuming and frequently produces unrealistic images. Therefore, other methods are sought that would exploit a small subset of sample real-world images for rapid database prototyping. This paper presents a fast and simple method of high-resolution target image insertion into a low-resolution image of a terrain. The method exploits a naive physics paradigm. First, a high-resolution target image is diffused using a Gaussian kernel and on-target zooming effect. A target binary mask guides the diffusion process. The diffused image is re-sampled onto a low-resolution target image. Next, a down-sampled target image is inserted into a given terrain image using two target insertion/diffusion processes and additional effects. These diffusion processes eliminate contrasts at the border area of a target and on the terrain/background. Background-to-target diffusion extends the heat of overlapped terrain pixels over a target section. Target-to-background diffusion radiates and overlaps target heat over the border area of the adjacent section of the terrain. Developed processes mirror the physics of heat propagation and diffusion, and apply weighted pixel mixing to eliminate target insertion contrasts. Given a set of high-resolution turntable data and a set of terrain images, a training database can be generated within a short time. The number of parameters controlling the insertion process has been decreased to the minimum and brought into a control panel. Each parameter has understandable physical meaning and has assigned a meaningful range of values.

The current state of the art in synthetic radiometrically accurate scene generation for visual signatures remains immature. Even more difficult is creating composite images of photo-realistic synthetic images placed into images of real scenes. A potential solution to this problem is to use measured background data to drive the target rendering process. This approach has the advantage of deriving synthetic images with sufficient fidelity for inputs into the visual laboratory and performance codes. Since scene luminance can change rapidly, especially during partly cloudy conditions, all measurements must be obtained nearly simultaneously. This paper will explore the requirements for a visual predictive code and meeting these requirements with a background measurement process. A prototype measurement system will be described along with results from measurements.

In order to find an optimal scanning strategy we determined the relationship between search performance and several scanning- and scene parameters in human observer experiments. The observers searched with a limited field of view (FOV) through a large search sector for a target (a camouflaged person) on a heath. From trial to trial the target appeared at a different location. Predefined (horizontal) scan paths were used with constant speed. The subjects hit a button as soon as the target was spotted. We determined the effect of scanning speed, zoom factor, FOV width and target location on search performance (detection time and probability). We also obtained estimates of target conspicuity for all targets and determined the relationship between conspicuity and search performance. We found that search performance was largely determined by the angular scanning speed of the simulated camera, and largely independent of zoom factor. The results show that conspicuity can be used to predict search performance in search with a limited FOV (this was previously shown for unrestricted search). Target conspicuity decreased when the targets appeared closer to the horizon (and where therefore more distant). Such a systematic dependency between target conspicuity and target location can be (and is probably) used by the observers to optimized search performance. The results further show that a reduction in the FOV width affects search performance when the time that a target is visible falls below a certain value (in our case about 1 sec). These findings can be used in future models of search performance with a limited FOV.

In field tests to compare the observability of combat vehicles, the test designer must select the optimum number of observation opportunities in order to balance collecting enough data to draw valid conclusions against the high cost of supporting vehicles and personnel at a test site. The test designer, however, generally lacks key parameters for the efficient design of the test. Namely, the designer lacks the detection probabilities of the vehicles at each range. The standard deviation of the difference in detection probability depends upon the detection probability itself. Therefore, the test designer must select the number of observations for each range based upon the conservative assumption that the probabilities are near 50%, the probability for the maximum standard deviation. In this paper, an iterative technique of test design is explored in order to improve the efficiency of observability tests.

High detection probabilities with low false alarm rates, even in the presence of as much as - 28 dB signal to clutter can be obtained, if use is made of the coherence information contained in the input signal. Such a detection system is described and its Receiver Operating Curves (ROC) characterized from a reduced experimental set of data. The system has an input filter with a rectangular passband, an interferometer and a photodetector. The filter gives rise to a sinc function shaped interferogram envelope in optical path difference. The position of the interferogram's first null depends on the effective bandwidth of the scene in the instrument's field of view. The detection system is sensitive to the degree of coherence of the scene. The amount of the shift of the position of the first null is found to be a highly sensitive measure of the presence of a very narrow-band target within the instrument's input bandpass filter. An important characteristic of this system is that the shift is still detected even when an intense wideband incoherent source, which may be considered to be clutter, is introduced into the input. We measured the ROC curves for the optical detection system using a He-Ne laser narrowband coherent source target with a tungsten halogen bulb wideband incoherent background clutter. We show that the target source can be detected even when it is substantially weaker than the clutter at - 28 dB signal to clutter. We compare the predictions of our theoretical model with the experimental results and show good agreement.

A new physical, non-stochastic N-d model for target discrimination is presented. The model is based on Tensor Invariants and overrides usual stochastic procedure limitations problems characterized by FP and FN. The computational model is related directly to physical world, and it offers three major operational advantages over previous methods, at least. The first advantage is progressive automatic model generation of the Complete Minimum Set of Tensor Invariants. The second one is the reduced computational power requirements over traditional method. Finally, target precision drives automatic model generation trough subsequent steps. In fact, model precision is increased at each step. Robust discrimination or machine number representation saturation ends the computational process. Machine number representation saturation state suggests more power computational resource requirements for critical mission achievement. The general approach is tested on selected 2-D image database and preliminary results are presented.

Multispectral IR imaging techniques are frequently deployed in maritime operations, for instance to detect floating mines or to find small dinghies and swimmers during search and rescue operations. However, maritime backgrounds usually contain a large amount of clutter that severely hampers the detection of dim point targets. Here we present a simple algorithm that deploys the correlation between target signatures in two different (3-5 and 8-12 mm) IR frequency bands to reduce the amount of clutter. First, both individual IR bands are filtered with a morphological opening top-hat transform to extract small details. Second, the resulting detail images are thresholded to produce binary detail images, representing potential target areas. Third, a fused detail image is obtained by taking the intersection (logical AND) of both binary IR detail images. Details that appear in both IR bands remain in this fused detail image, whereas a large fraction of uncorrelated noise details is filtered out. Remaining noise details can be removed by taking into account the temporal characteristics of the target signatures and by using a priori knowledge of structure of the scene and the size of potential targets. The method is tested on two image sequences showing a maritime scene with three kayaks approaching from far away. The scenario was registered in the 3-5 mm and 8-12 mm IR frequency bands, and in the visual range. The results show that the proposed multispectral processing technique has the potential to improve the detection of dim point targets in cluttered maritime backgrounds.

Acoustic signatures are being exploited more and more by new technology in the battlefield as a way of detecting and identifying potential targets. An understanding of the way in which the acoustic signature of a land platform propagates through the atmosphere enables one to target suppression techniques to those acoustic sources on the vehicle that will provide the greatest military benefit in terms of reducing the detection range of the platform. Dstl Chertsey (UK) and TACOM (US) have developed acoustic propagation models which can predict the far-field sound pressure levels (SPLs) and associated detection ranges of land platforms under a variety of meteorological conditions over different terrain types. The Acoustic Prediction Propagation Model (APPM), UK) and Acoustic Detection Range Prediction Model (ADRPM, US) have previously been compared and have been found to produce similar results for simple scenarios. With recent developments in both models, this comparison has been carried out again, looking at the introduction of Fast-Field Programs (FFP) to both models and, in more detail, the differences between the results at certain frequencies. This paper represents the results found from this comparison study, showing the differences, similarities and potential of these models for the future.

There is a push in the Army to develop lighter vehicles that can get to remote parts of the world quickly. This objective force is not some new vehicle, but a whole new way of fighting wars. The Future Combat System (FCS), as it is called, has an extremely aggressive timeline and must rely on modeling and simulation to aid in defining the goals, optimizing the design and materials, and testing the performance of the various FCS systems concepts. While virtual prototyping for vehicles (both military and commercial) has been around as a concept for well over a decade and its use is promoted heavily in tours and in boardrooms, the actual application of virtual protoyping is often limited and when successful has been confined to specific physical engineering areas such as weight, space, stress, mobility, and ergonomics. If FCS is to succeed in its acquisition schedule, virtual prototyping will have to be relied on heavily and its application expanded. Signature management is an example of an area that would benefit greatly from virtual prototyping tools. However, there are several obstacles to achieving this goal. To rigorously analyze a vehicle's IR and visual signatures extensively in several different environments over different weather and seasonal conditions could result millions of potentially unique signatures to evaluate. In addition, there is no real agreement on what evaluate means or even what value is used to represent signature; Delta T( degree(s)C), Probability of Detection? What the user really wants to know is: how do I make my system survivable? This paper attempts to describe and then bound the problem and describe how the Army is attempting to deal with some of these issues in a holistic manner using SMART (Simulation and Modeling for Acquisition, Requirements, and Training) principles.

The advent of low-observable (stealth) ships, of which the new Air Defense and Command Frigate (LCF) is an example, must be followed by an increased interest in signature control during operations. Taking full operational advantage of the stealth character of low-observable ships requires on-board signature control. At all times, the ship's visibility for expected threats must be known. This paper presents an active infrared-signature control system, that will be used on board the LCF. The system is the first step towards a full signature management system, which takes into account all systems affecting the signature during operations. Such a system should not only consider electro- optical signatures, but all relevant signatures: radar, acoustic, magnetic, etc.

An evaluation tool for the effectiveness of infrared decoys against anti-ship missiles has been built. In a flexible software setup, different methods of preprocessing and detection can be chosen for the processing of recorded infrared image sequences. Since a flying missile seeker with a variable speed and variable starting distance is simulated, the recorded images, from a static camera or a camera moving at relatively low speed, are corrected before they are fed into the seeker algorithm of the simulated missile. MODTRAN and the Naval Aerosol Model are used to calculate the atmospheric transmission effects in the preprocessing. The hot spot seeker algorithm uses features such as contrast and position above or below the horizon to differentiate between ship, infrared decoys and false alarms resulting from clutter. During the simulation the track window of the seeker is visualized on the recorded images. The aim point of the missile during the flight is logged in a file to enable evaluation. With this tool the effectiveness of a recorded decoy deployment in various scenarios can be evaluated by varying the missile parameters such as distance between missile and ship when the first decoy is deployed, missile search algorithm, and missile track algorithm.

An example of how gray-level co-occurrence matrix (GLCM) trackability metric (TM) can be used to evaluate a concealing countermeasure is presented. In this example the effect of multispectral waterfog as a countermeasure for an armored vehicle is evaluated. The results are also compared to results from a correlation tracker. A careful analysis of GLCM TM results showed that multispectral waterfog is effective against a target tracker. This analysis includes a comparison to an actual tracker simulation, a contrast analysis, and an analysis of the uncertainty histograms used in the GLCM TM calculation.

The Ontar Corporation (www.Ontar.com) is well known for its products for atmospheric remote sensing to calculate radiative transport, atmospheric transmission, and sensor performance in both the normal atmosphere and the atmosphere disturbed by battlefield conditions of smoke, dust, explosives and turbulence. This paper will describe new research activities at Ontar to enhance both the user capabilities and the model functionality. Ontar has incorporated new models into our software products and has initiated an ambitious IR&D effort to further enhance the models. This paper will discuss these efforts. We will also discuss new software products and updates to existing software products that we are distributing. This includes a new release of NVTherm; updates to PcModWin and PcLnWin; and a high resolution gas absorbance spectral database from the Pacific Northwest National Laboratory's (PNNL) spectral data library.

To assist in design and optimization processes, the standard atmospheric profiles have been investigated. This study has been both phenomenological and statistical, within the confines of available databases. The original standard atmosphere profile dataset was collated using radiosonde data thirty years ago, with general applications in mind, rather than specifically IR propagation applications. These data have been revisited and compared with a compilation of a large number of radiosonde data used for atmospheric retrieval initial estimations (the TIGR database). Although in general the LOWTRAN standard atmospheres represent reasonable mean conditions, these models do not cover the design limits required for IR systems.

A scanning backscatter lidar, operating at a wavelength of 1.06 micrometers , was used to measure the volume backscatter coefficient of coastal aerosol at the Mace Head Research Station on the west coast of Ireland during the PARFORCE experiments in September 1998 and June 1999. Lidar measurements under a fixed elevation angle at fixed time intervals provided the depth and evolution of the boundary layer throughout the day. Horizontal scans over the bay near the station indicate that waves breaking on the small islands and rocks in the bay near the station generate coherent plumes of a few hundred meters wide that propagate over distances of more than 5 km. Vertical scans have shown that the initial height of these plumes is a few tens of meters, rising to several hundreds of meters while advected over several kilometers. The backscatter coefficient in the plumes was between a factor of 2 and 10 higher than outside the plume. Large series of consecutive vertical cross sections showed that patches of aerosol plumes are taken aloft in the boundary layer to altitudes of more than one kilometer. So far, no relation was found between the horizontal and/or the vertical extent of the aerosol plumes and the air-to-sea temperature difference. The lidar measurements indicate that in situations that the wind is from over one of the islands the ambient aerosol concentrations can be enhanced by more than a factor 2 due to local aerosol sources.

The continuing effort to provide a complex, broad-based (low-background, complex dynamic scene projection) sensor test capability at Arnold Engineering Development Center involves the development of scene projection technologies and their integration into existing space chambers. New radiometric source concepts are being investigated that will allow greater flexibility in simulating multiple target scenarios for space sensor testing. Alternate sources, filtering techniques, beam combining methods, and optical power delivery systems are being investigated for possible use in meeting the ultimate objectives of current and anticipated testing programs.

The question of whether it is always appropriate to assume in the generation of synthetic, single broadband midwave infrared (MWIR) imagery that the emissivities of scenery objects are constants with respect to wavelength is addressed. In the radiometric measurement equation, the detector signal due to the image plane irradiance within a finite waveband is proportional to the integral of the detector spectral responsivity times the scene radiance, and the scene radiance is the directional spectral emissivity of the scene times the spectral radiance of a blackbody at the same temperature. Using the spectral emissivity data of a set of commonly encountered scenery materials and different temperatures, single broadband MWIR image signals from idealized thermal and InSb-type photon detectors were computed using the measurement equation with spectral emissivity and detector responsivity and with several emissivity and detector responsivity approximations for comparison. The results show a strong correlation between the relative variation, or fractional standard deviation, of the average MWIR emissivity and the error in the emissivity/responsivity approximation results relative to the spectral emissivity/responsivity results.

We examine the relationship between atmospheric-induced clutter, driven mainly by temporal variations of obscuring aerosols, and the more usual clutter attributed to spatial variations in natural background scenes. Our main approach is through the analysis of time dependent transmission-radiance measurements obtained during field experiments and through existing theories exploited in atmospheric models for generating effects of natural weather types and man made (battlefield) obscurants. We couple the obscurant modeling with other existing models for simulating natural background scenes and examine the effects of the obscurants on various scenes using recently developed analytical methods for calculating clutter metrics. Our selected clutter metric is based on what we call the block filter method that quantifies IR clutter in terms of potential false targets based on scene statistics. Our main focus is on the effects of direct transmittance, path radiance, and turbulence driven noise at multiple wavelength regimes. Preliminary results from field data show strong cross-band correlations in measured path transmission obtained over collinear lines of sight and wavelengths from the visible to infrared. The same trend holds for measured path radiance, most rigorously at the shorter wavelengths (visible and near infrared), but with a significantly enhanced noise component at the infrared wavelengths (mid and far infrared) where the effect of obscurant thermal emission comes into play. From the analysis of the imagery we have also detected both emissive and reflective contributions to the path radiance. We apply the results to four background scenes of varying degree of complexity and report the results in terms of a clutter metric representative of the particular background under both clear air and obscured conditions.

Two characteristics are critical in the understanding of target signatures, physical surface temperature and surface reflectance. An objects surface reflectance can be thought of as having two major components, the diffuse and specular components. The best way to understand these components is by examining the Bi-directional Reflectance Distribution Function (BRDF). The BRDF provides an understanding of the reflectance behavior of a surface from every incident angle and reflectance angle. With the BRDF one can provide an accurate computer model of how the material behaves. Databases of BRDF data are available for use in modeling and simulation of targets but are typically comprised of pristine samples that may not be representative of real world targets. This paper will provide methods, data and trends of the BRDF variability in the infrared regions. We will also explore appropriate data sets for use to represent typical fielded targets.

We have been conducting research aimed at enabling prediction of desert optical environments from meteorological and satellite observations. To this end we have been collecting aerosol size distributions, visibility and meteorological data continuously for the past year at 2 sites in the Mojave Desert of California. Optical properties of dust are calculated from these data for a great variety of meteorological conditions. The concentration of dust particles is strongly dependent on wind speed for speeds greater than a threshold (7 m/s at Edwards and 15 m/s at China Lake). For individual wind episodes there is a clear relationship between wind speed and dust mass. However, that relationship changes from event to event leading to noisy summary plots; thus, indicating that other factors, such as dust sources, also influence dust loading. The HYPACT program is used to map out the sources, concentration and flow of dust. HYPACT is a pollution transport program that uses RAMS meteorological code output for input. HYPACT can calculate concentration forward in time from an assumed emission source or backward in time from an observation site. This facilitates the location of dust sources and the calculation of dust concentrations along air streams. Once dust concentrations are known and assuming the particle size distributions are the same as at the measurement sites knowledge of IR extinction is no longer confined to just the measurement sites.

A laboratory prototype reflectometer with applications in scene content characterization is available at the Arnold Engineering Development Center (AEDC), Arnold AFB. The SCAT/R measures specular, total, and retro-reflectance at five angles of incidence (AOI) scanning from 2.5 to 15 micrometers . Diffuse reflectance, total integrated scatter (TIS), and thermal emittance are calculated from the measurements. Conventional TIS measurements provide a good measure of a surface finish deviation from specularity, but the scatter distribution is not obtainable from a single measurement. By making TIS measurements over a series of AOI, information on the distribution is obtained. For example, a diffuse surface can be evaluated to determine whether the scattering is characterized by a Lambertian distribution. It has been observed that a series of retro-reflectance measurements at various AOI yields similar angle resolved information. In this paper, the relationship between retro-reflectance and TIS as a function of AOI is investigated for various materials using data from SCAT/R scans. The presentation and analysis of the data follow a brief description of the instrument. The SCAT/R thermal infrared data is useful in identifying/cataloging polarization and hyperspectral characteristics of materials and coatings used for camouflage and for other target and background applications.

For applications like missile warning and automatic target recognition, AIM is presently launching its new 3rd generation high speed dual-color module. The focal plane array (FPA) is a mercury cadmium telluride (MCT) 192x192 56micrometers pitch device in a dual-color mid wave (MWIR) design. The module provides spectral selection with temporal and spatial coincidence for both colors using a new AIM proprietary technology. The spectral bands presently selected are 3.4-4 and 4.2-5micrometers with a full frame rate of 870Hz. Prior to the new devices, a sequential multicolor MCT camera with broadband detector and spectral selection using a rotating filter wheel was developed and evaluated. Results are shown to demonstrate the capabilities of spectral selective detection specifically for clutter and false alarm suppression in missile warning applications. A new algorithm was developed to allow highly sensitive detection of missile plumes without any need for non-uniformity correction for long-term stable operation and maximum dynamic range. An outlook is given on new activities at AIM on dual-band devices. The dual-band approach combining mid wave (MWIR) and long wave (LWIR) detection is specifically useful in automatic target recognition. The application, existing devices and the design goal of the new dual-band device are discussed together with experimental results.

Modern anti-tank missiles and the requirement of rapid deployment have significantly reduced the use of passive armour in protecting land vehicles. Vehicle survivability is becoming more dependent on sensors, computers and countermeasures to detect and avoid threats. An analysis of missile propellants suggests that missile detection based on plume characteristics alone may be more difficult than anticipated. Currently, the passive detection of missiles depends on signatures with a significant ultraviolet component. This approach is effective in detecting anti-aircraft missiles that rely on powerful motors to pursue high-speed aircraft. The high temperature exhaust from these missiles contains significant levels of carbon dioxide, water and, often, metal oxides such as alumina. The plumes emits strongest in the infrared, 1 to 5micrometers , regions with a significant component of the signature extending into the ultraviolet domain. Many anti-tank missiles do not need the same level of propulsion and radiate significantly less. These low velocity missiles, relying on the destructive force of shaped-charge warhead, are more difficult to detect. There is virtually no ultraviolet component and detection based on UV sensors is impractical. The transition in missile detection from UV to IR is reasonable, based on trends in imaging technology, but from the analysis presented in this paper even IR imagers may have difficulty in detecting missile plumes. This suggests that the emphasis should be placed in the detection of the missile hard body in the longer wavelengths of 8 to 12micrometers . The analysis described in this paper is based on solution of the governing equations of plume physics and chemistry. These models will be used to develop better sensors and threat detection algorithms.

As methods continue to develop for predicting infrared signatures for complex propulsion systems, the need to validate such methods and, indeed to gain confidence in new designs grows. Within Dstl, work to develop static engine test rigs has been carried out. These rigs allow aspects of infrared signature such as plume mixing, cavity emissions, surface impingement and subsequent treatment, obscuration and nozzle shaping to be studied. However, there is a growing need for data, which is more closely related to actual flight conditions. Full flight measurements are prohibitively expensive and often out of the question when a range of geometries are to be studied. Wind tunnel tests can also be difficult because of the quantity of power required for the free stream flow and the need to produce realistic hot gas. This paper describes the work that has been carried out to produce a cost effective free stream measurement capability, which makes use of existing static engine facilities. By bleeding engine compressor flows and exhaust flows, a reduced scale system has been created which allows the simulation of infrared propulsion issues at free stream Mach numbers of up to 0.5. The data obtained with this system has been used to validate the prediction methods for 3D-exhaust plume and afterbody infrared signature.

An active MilliMeter Wave (MMW) system exploiting forward squinting Synthetic Aperture Radar (SAR) techniques can provide high resolution imagery. Such a radar offers a compact, all weather, day/night solution to the problem of accurate airborne navigation. Interpreting radar imagery of very cluttered urban areas is challenging, thus complicating autonomous navigation within such areas. For example, imagery is subject to effects such as layover distortions due to the height of buildings and also considerable radar shadowing. In this paper we examine the use of synthetic imagery to capture the key elements of the radar imagery. The MMW imagery can then be related to the physical models from which the synthetic imagery is generated leading to improved scene understanding. This paper describes the modeling process adopted and compares real imagery from a 35GHz forward squinting SAR radar with the synthetically generated imagery. The modeling process includes provision for terrain undulation, man-made and natural clutter regions and the ability to generate a sequence of imagery from a specified flight path. Examples presented include a representative urban area containing a variety of building structures. An important part of this research is the required fidelity of the synthetic scene model and therefore investigations into the level of detail required are also presented. Further work aims to exploit the synthetic imagery for navigational purposes through registration with the actual radar image thereby automatically locating key building structures with the imagery.

Research in the area of air-to-ground target detection, track and identification (ID) requires the development of target signal models for known geometric shapes moving in ground clutter. Space-time adaptive filtering techniques in particular make good use of temporal-spatial synthetic radar signal return data. A radar signal model is developed to generate synthetic wideband radar signal data for use in multi-channel adaptive signal processing.

An analysis of target separability has been performed under an OSD Target Management Initiative program entitled Radar Variations. The program has concentrated on analyzing radar signatures from multiple main battle tanks (MBTs) in order to quantify the differences in Ka-band signatures of vehicles due to intraclass and interclass target variations. As a significant factor in the success of the Radar Variations program, U Mass Lowell's Submillimeter-Wave Technology Laboratory (STL) and U.S. Army National Ground Intelligence Center (NGIC) fabricated 1/16th scale exact replicas of the vehicles used in the Ka-band radar signature acquisition study directed by Simulation Technologies, Inc. (SimTech) and Targets Management Office (TMO). These replicas enabled NGIC to measure statistically significant amounts of high-fidelity signature data for a variety of target configurations with an indoor compact radar range.

A new 3D radiative code is used to solve the radiative transfer equation in the UV spectral domain for a nonequilibrium and axisymmetric media such as a rocket plume composed of hot reactive gases and metallic oxide particles like alumina. Calculations take into account the dominant chemiluminescence radiation mechanism and multiple scattering effects produced by alumina particles. Plume radiative properties are studied by using a simple cylindrical media of finite length, deduced from different aerothermochemical real rocket plume afterburning zones. Assumed a log-normal size distribution of alumina particles, optical properties are calculated by using Mie theory. Due to large uncertainties of particles properties, systematic tests have been performed in order to evaluate the influence of the different input data (refractive index, particle mean geometric radius) upon the radiance field. These computations will help us to define the set of parameters which need to be known accurately in order to compare computations with radiance measurements obtained during field experiments.

The information presented about the active protection system (APS) AWiSS was and is still funded by the German procurement agency (BWB) as part of the definition phase for an new generation of light armored vehicles It outlines the results achieved in the area of signature and vulnerability data collection and analysis of anti-tank munitions. A overview is given about the program areas where anti-tank munitions signature data are used.

As a result of the deployment of UV missile warning systems, recent years have seen an increasing interest in threat assessment in the UV band. Unfortunately, due to the different nature of the physical processes that are needed to describe a missile signature in the UV, available codes for the IR can not be applied. As a result, the development of a UV missile plume signature model was initiated. This paper presents a model for the prediction of UV missile plume signatures, that takes into account relevant physical mechanisms in a missile plume. The model is based on first principles, predicting the radiance from CO-O chemiluminescence and hot particles in the plume, which are the dominant sources of radiation in the UV wavelength band considered. Scattering of radiation on particles in the plume can be important for particle-rich propellants and is accounted for in the code. The multiple scattering algorithm has been set up to handle any number of directions in an axi-symmetric medium; the algorithm presents a novel way of solving the radiative transfer problem. Several examples are shown, to illustrate scattering processes in missile plumes. A number of validation tests are presented to show the model's performance. At this stage, comparisons with real data are under progress.

The United States Army Space and Missile Defense Command (USASMDC) has interest in a technology demonstration that capitalizes on investment in fire control and smart interceptor technologies that have matured beyond basic research. The concept SWORD (Short range missile defense With Optimized Radar Distribution) consists of a novel approach utilizing a missile interceptor and interferometric fire control radar. A hit-to-kill, closed-loop, command guidance scheme is planned that takes advantage of extremely accurate target and interceptor state vectors derived via the fire control radar. The fire control system has the capability to detect, track, and classify multiple threats in a tactical regime as well as simultaneously provide command guidance updates to multiple missile interceptors. The missile interceptor offers a cost reduction potential as well as an enhancement to the kinematics range and lethality over existing SHORAD systems. Additionally, the Radio Frequency (RF) guidance scheme offers increased battlefield weather performance. The Air Defense (AD) community, responding to current threat capabilities and trends, has identified an urgent need to have a capability to counter proliferated, low cost threats with a low cost-per-kill weapon system. The SWORD system will offer a solution that meets this need. The SWORD critical technologies will be identified including a detailed description of each. Validated test results and basic principles of operation will be presented to prove the merit of past investments. The Deputy Assistant Secretary of the Army for Research and Technology (DAS(R&T) has a three- year Science and Technology Program to evaluate the errors and proposed mitigation techniques associated with target spectral dispersion and range gate straddle. Preliminary bench-top experiment results will be presented in this paper.

The differentiated and multi-spectral threat of the future battlespace sets new demands on ground platforms. This has implications on the whole development process of future ground systems. In the Swedish Signature Management Program SAT/Mark, these issues have been in focus during the last five years. Results from this research and development effort are presented with emphasis on system engineering, simulation and validation of signatures.

The Advanced Ray Tracing with Earth Atmospheric Models (ARTEAM) aims at a description of the electro-optical propagation environment in the marine atmospheric surface layer. For given meteorological conditions, the model evaluates height- and range-resolved transmission losses, refraction and turbulence effects. These results are subsequently applied to an electro-optical sensor with given specifications to evaluate the effective range and performance of the sensor under the prevailing meteorological conditions. Finally, for specified sensor-target geometry, the model calculates characteristic parameters for geometrical and spectral intensity, scintillation, blur and image distortion. ARTEAM is developed with an extensive Graphical User Interface (GUI) for Windows environments.

During the development of smart weapon's seeker/sensors, it is imperative to collect high quality signatures of the targets the system is intended to engage. These signatures are used to support algorithm development so the system can find and engage the targets of interest in the specific kill area on the target. Englin AFB FL is the AF development center for munitions; and in support of the development effort, the 46th Test Wing (46 TW) has initiated significant improvements in collection capabilities for signatures in the MMW, Infrared and Seismic, Acoustic and Magnetic (SAM) spectrum. Additionally, the Joint Munitions Test and Evaluation program office maintains a fleet of foreign ground vehicle targets used for such signature collection including items such as tanks, SCUD missile launchers, air defense units such as SA-06, SA-8, SA-13, and associated ground support trucks and general purpose vehicles. The major test facility includes a 300 ft tower used for mounting the instrumentation suite that currently includes, 10, 35 and 94 GHz MMW and 2-5(mu) and 8-12(mu) IR instrumentation systems. This facility has undergone major improvements in terms of background signature reduction, construction of a high bay building to house the turntable on which the targets are mounted, and an additional in- ground stationary turntable primarily for IR signature collection. Our experience using this facility to collect signatures for the smart weapons development community has confirmed a significant improvement in quality and efficiency. The need for the stationary turntable signature collection capability was driven by the requirements of the IR community who are interested in collecting signatures in clutter. This tends to be contrary to the MMW community that desires minimum background clutter. The resulting location, adjacent to the MMW tower, allows variations in the type and amount of clutter background that could be incorporated and also provides maximum utilization of the existing tower to mount the instrumentation suite or seeker and the in-place electronic support facilities. Additionally, major equipment improvements in SAM instrumentation and a SAM van have been acquired to provide a mobile SAM signature collection capability.

The information presented about the active protection system (APS) AWiSS was and is still funded by the German procurement agency (BWB) as part of the definition phase for an new generation of light armored vehicles. The requirements concerning general system approach, the AWiSS system design and the systems specification are presented. Program related milestones and demonstrations are discussed.