The paper describes a Mid-wave Infrared (MWIR) Panoramic Sensor using existing focal plane array (FPA)
technologies and commercially available IR optics, and packaged in a relatively simple and rugged manner to provide a
360° azimuth and 60° elevation field-of-view (FOV) coverage, without any scanning mirror. This sensor can be
deployed for initial target tracking, situational awareness, perimeter security, and other applications. The basic
performance and parameters of the Sensor, such as mechanical, electrical interfaces, optical parameters, etc. are also
included. Some basic sensor performance analysis (such as target signal-to-noise ratio verses range and background
level), and field testing results are also presented and compared for some simple levels of processing.
KEYWORDS: Receivers, Sensors, Transmitters, Scintillation, Scanners, Modulation, Telecommunications, Transponders, Data acquisition, Global Positioning System
Laser based free-space-optical communication (FSOC) links are known to provide covert, secure, jam-proof and very
high bandwidth performances. For mobile platforms, precision pointing and tracking schemes are critical for continuous
guiding of a modulated laser beam to establish data link maintenance. In this paper, preliminary experiments of an
angle-discrimination based smart pointing and tracking scheme suitable for high-speed, closed-loop, FSOC is discussed.
A dual-axis, high-speed, galvo-mirror based scanner was utilized for conical scanning at 550 Hz. Greenwood frequency
in the presence of moderate atmospheric turbulence over a range of 1 km at 1.5 μm was measured. It is shown that
selection of a scan frequency much higher than the Greenwood frequency reduces scintillation effects on scan angle
measurements for track loop maintenance. The measured scan angle value of the receiver with respect to transmit beam
when fed back to the scanner through an optical transponder would allow pointing error estimation and correction.
Based on our initial phenomenology study, it is shown that the scan-angle modulation based pointing and tracking
scheme would provide data-link reliability for dynamic platforms traveling on rough terrains.
Critical elements of future exoatmospheric interceptor systems are intelligent processing techniques which can effectively combine sensor data from disparate sensors. This paper summarizes the impact on discrimination performance of several feature and classifier fusion techniques, which can be used as part of the overall IP approach. These techniques are implemented either within the fused sensor discrimination testbed, or off-line as building blocks that can be modified to assess differing fusion approaches, classifiers and their impact on interceptor requirements. Several optional approaches for combining the data at the different levels, i.e., feature and classifier levels, are discussed in this paper and a comparison of performance results is shown. Approaches yielding promising results must still operate within the timeline and memory constraints on board the interceptor. A hybrid fusion approach is implemented at the feature level through the use of feature sets input to specific classifiers. The output of the fusion process contains an estimate of the confidence in the data and the discrimination decisions. The confidence in the data and decisions can be used in real time to dynamically select different sensor feature data, classifies, or to request additional sensor data on specific objects that have not been confidently identified as 'lethal' or 'non-legal'. However, dynamic selection requires an understanding of the impact of various combinations of feature sets and classifier options. Accordingly, the paper presents the various tools for exploring these options and illustrates their usage with data sets generated to realistically simulate the world of Ballistic Missile Defense interceptor applications.
This paper presents the methodology and assessment of the passive and active sensor feature selection algorithms of interest to the Discriminating Interceptor Technology Program (DITP), as applied to aimpoint selection. The analysis identifies the performance achieved by utilizing individual sensor features and multi-sensor feature fusion. Traditional methods of determining the proper aimpoint have depended upon identifying target characteristics such as the geometric centroid, radiometric centroid, leading edge, and the trailing edge. Once these target points have been defined, the final aimpoint is selected by adding a bias to the target characteristic. However, these and similar algorithms have shown sensitivity to a priori knowledge of the threat, such as aspect angle, target length, thermal and dynamic characteristics. This paper will assess the utility of multi-sensor disparate sensor data to decrease performance sensitivity to a priori knowledge of the threat. These algorithms are among the feature selection algorithms in use in the DITP program for a passive and active fused sensor discrimination. The analysis utilizes simulated IR and ladar sensor data of a conical body that is initially at sufficient range to be realized as a slightly extended source on the focal plane, and then advanced through the later phase of the engagement to the point where the target is relatively close and highly resolved. The measures of performance consist of evaluating the deviations of the estimated aimpoint versus range to target, orientation angle, and aspect angle, for the feature selection algorithms considered.
Intelligent processing techniques which can effectively combine sensor data from disparate sensors by selecting and using only the most beneficial individual sensor data is a critical element of exoatmospheric interceptor systems. A major goal of these algorithms is to provide robust discrimination against stressing threats in poor a priori conditions, and to incorporate adaptive approaches in off- nominal conditions. This paper summarizes the intelligent processing algorithms being developed, implemented and tested to intelligently fuse data from passive infrared and active LADAR sensors at the measurement, feature and decision level. These intelligent algorithms employ dynamic selection of individual sensors features and the weighting of multiple classifier decisions to optimize performance in good a priori conditions and robustness in poor a priori conditions. Features can be dynamically selected based on an estimate of the feature confidence which is determined from feature quality and weighting terms derived from the quality of sensor data and expected phenomenology. Multiple classifiers are employed which use both fuzzy logic and knowledge based approaches to fuse the sensor data and to provide a target lethality estimate. Target designation decisions can be made by fusing weighted individual classifier decisions whose output contains an estimate of the confidence of the data and the discrimination decisions. The confidence in the data and decisions can be used in real time to dynamically select different sensor feature data or to request additional sensor data on specific objects that have not been confidently identified as being lethal or non- lethal. The algorithms are implemented in C within a graphic user interface framework. Dynamic memory allocation and the sequentialy implementation of the feature algorithms are employed. The baseline set of fused sensor discrimination algorithms with intelligent processing are described in this paper. Example results from the algorithms are shown based on static range sensor measurement data.
Intelligent processing techniques are applied to a ballistic missile defense (BMD) application, focused on classifying the objects in a typical threat complex, using fused IR and ladar sensors. These techniques indicate the potential to improve designation robustness against 'off-normal'/unexpected conditions, or when sensor data or classifier performance degrades. A fused sensor discrimination (FuSeD) simulation testbed was assembled for designation experiments, to evaluate test and simulation data, assess intelligent processor and classification algorithms, and evaluate sensor performance. Results were produced for a variety of neural net and other nonlinear classifiers, yielding high designation performance and low false alarm rates. Most classifiers yield a few percent in false alarm rate; rates are further improved when multiple techniques are applied vi a majority based fusion technique. Example signatures, features, classifier descriptions, intelligent controller design, and architecture are included. Work was performed for the discriminating interceptor technology program (DITP).
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