Optimal Algorithm Development for UHF Circular Synthetic Aperture Radar (CSAR) Applications

The use of circular synthetic aperture radar (CSAR) acquisition geometry can help to overcome some of the limitations imposed by currently available SAR technologies for sensing small targets in complex environments. CSAR data are collected over a full 360 degree azimuthal range by flying circular flight geometry while retaining focus on a target. CSAR image formation can be approximated by dividing circular arcs into small straight line trajectories, forming a subaperture. Existing fast backprojection algorithms can be then used for 2- and 3-D image formation. These image formation algorithms have been successful at generating high-resolution images for linear flight geometries, but key issues remain in formatting and applying them for accurate and efficient processing. Sky Research and its partners propose an optimal near real-time computing architecture for high resolution CSAR data processing through the use of novel algorithm development and parallel and distributed computing methods. The proposed approach combines distributed and concurrent computing for CSAR providing significant performance and image quality enhancements over conventional single processor techniques. The algorithm combines fast time-domain backprojection, coherent integration with innovative memory management, and change detection. A simple analytical model is proposed that allows assessment of the impact on performance of practical, application-specific properties. BENEFIT: The anticipated benefits of the proposed CSAR technology are significant to Department of Defense (DoD). These include the following: (1) A significant reduction in the time needed to form CSAR images. Simultaneous collection and transfer of data to a multi-core processing computer in the aircraft is expected to put real-time CSAR image exploitation within reach and open up a full 3D imaging and analysis capability for airborne intelligence assets. (2) Increased probability of detection and reduced false alarm rate. The successful implementation of this CSAR technology will lead to both higher quality imaging and target detection for ISR applications and higher efficiency and utility through the realization of near real-time processing. (3) Potential for very high resolution 3D imaging and ATR products. Numerical studies and limited experimental data have shown that CSAR can achieve 3D images and higher resolution than conventional linear SAR acquisition and imaging. (4) High fidelity persistent ISR and CCD. Improvements in image formation time will enable coherent and non-coherent change detection. High resolution imaging combined with change detection should dramatically increase our ability to push near real-time intelligence down to decision makers in the field. Continuous staring at the target also provides for temporal change detection and potential video SAR capability. This will greatly enhance surveillance capabilities for moving target indicators and vigilant sensing of urban areas.