Ground-based surveillance of deep space has traditionally been the purview of optical telescope systems. Unlike their imaging counterparts, space surveillance telescopes emphasize wide field of view (FOV) over resolution, permitted the most rapid survey of the entire sky. At the same time there is a constant push to detect ever fainter objects, such as small pieces of space debris or small, distant asteroids. Unfortunately increased sensitivity requires very large aperture diameters, which when combined with the requirement for wide FOV results in very fast f/# telescopes. How far this set of requirements can be expanded is typically limited by large, complex, and costly corrector optics to flatten the wavefront. An alternative approach is to design the telescope to a curved focal plane. This is an approach that was once taken with film, but it has not been feasible with electronic focal plane arrays (FPA). A major break-through in FPA design may open up a new range of telescope design options. A new array fabrication technique now provides the ability to produce FPAs with a specified degree of curvature while preserving required electro-optical characteristics. This paper presents a design for a new space surveillance telescope utilizing these curved FPAs.
Acquisition of full-polarimetric millimeter-wave, or microwave, moving target signature sets sufficient for developing ATR algorithms have proven to be costly and difficult to achieve operationally. Thorough investigations involving moving targets are often hindered by the lack of rigorously consistent signature data for a sufficient number of targets across requisite viewing angles, articulations and environmental conditions. Under the support of DARPA's TRUMPETS and AMSTE programs in conjunction with the US Army National Ground Intelligence Center, X-band far-field turntable signature data has been acquired on 1/16th scaled models of the Bradley and BTR-70 vehicles specifically constructed for moving target investigations using ERADS' 160 GHz fully polarimetric compact range. The tracks/wheels of the scale models were translated incrementally as the radar's transmit frequency was stepped across a 10.5 Ghz bandwidth. By acquiring a full frequency sweep at each track/wheel position with appropriate translation resolution, HRR RCS profiles of Doppler-shifted body/track components were generated. HRR profiles of the equivalent stationary vehicle were also generated for analysis using the vehicle's HRR profiles for any given track position.
Today's radar exploitation system utilize information from both Ground Moving Target Indication (GMTI) and Synthetic Aperture Radar (SAR) obtained from various airborne platforms. GMTI detects and supports the classification of moving targets, whereas SAR detects and supports the classification of stationary targets. However, there is currently no ability to integrate the information from these two classes of radars in tracking targets that execute sequences of move-stop-move maneuvers. The solutions of this dilemma is the development of a Continuous Tracking (CT) architecture that uses distinctive GMTI and SAR features to associate stationary and moving target detections through move-stop-move maneuvers. This paper develops a theoretical model and present corresponding numeric computations of the performance of the CT syste. This theory utilizes a two- state Markov process to model the successive SAR and MTI detections are derived from typical traffic and sensor behaviors. This analysis of the sensor characteristics and the underlying traffic model provides a foundation in designing a CT systems with the maximum possible performance.
The understanding of maneuvering forces is invaluable to the warfighter, as it enhances understanding of enemy force structure and disposition, provides cues to potential enemy actions, and expedites targeting of time critical targets. Airborne ground moving target indicator (GMTI) radars are a class of highly-effective, all-weather, wide-area senors that aid in the surveillance of these moving ground vehicles. Unfortunately conventional GMTI radars are incapable of identifying individual vehicles, and techniques for exploiting information imbedded within GMTI radar reports are limited. The Defense Advanced Research Projects Agency (DARPA) Moving Target Exploitation (MTE) program is working to mitigate these deficiencies by developing, integrating, and evaluating a suite of automated and semi-automated technologies to classify moving targets and units, and to provide indications of their activities. These techniques include: aid in the interpretation of GMTI data to provide moving force structure analysis, automatic tracking of thousands of moving ground vehicles, 1-D target classification based upon high-range- resolution (HRR) radar profiles, and 2-D target classification based upon moving target imaging (MTIm) synthetic aperture radar (SAR). This paper shall present the MTE concept and motivation and provide an overview of results to date.
We investigate the phenomenology and modeling for the development of an active multispectral laser radar (LADAR) sensor to image and identify ground targets in the 1 to 5 micrometers wavelength region. This sensor will be especially useful in high clutter situations or situations where the target is partially concealed. A continuously tunable optical parametric oscillator using a periodically poled lithium niobate (PPLN) nonlinear optical crystal is investigated as a candidate light source for the sensor. A 1 micrometers Nd:YAG laser was frequency shifted in PPLN to produce continuously tunable output between 1.35 to 5 micrometers wavelengths and signal output energy of up to 3.3 mJ in a 3 ns pulse. A tunable monostatic reflectometer system is fabricate for the measurement of the bidirectional reflectance distribution function of the LADAR target materials A method or band selection is formulated and tested using library reflectance spectra. Results of this work will be used for tower based imaging of different targets in cluttered backgrounds at ranges out to 3 km.