Interrupted Synthetic Aperture Radar (intSAR)

ABSTRACT: SSCI proposes to investigate and finalize the design of a SAR imaging approach that provides the SAR user community with good quality complex SAR imagery from phase-history data having temporal and/or frequency data gaps. These data-gap interruptions maybe planned or spontaneous, cooperative or non-cooperative and may result from both friendly and/or hostile radio frequency interference (RFI). We will implement a MATLAB-based algorithm test bed to simulate and optimize the performance of the"gap-filling"approach the proposed solution will automatically detect and characterize the gapping pattern and will adapt the gap-filling algorithm to the gap pattern, optimizing the image formation process for utilization in various SAR image exploitation modes, including coherent/non-coherent change detection and target recognition by image analysts and/or automatic algorithms. SSCI will evaluate and characterize the effects of the phase-history data gaps on SAR image quality and image utility. Studies will be performed to quantify the quality of complex image features (coherence, mean absolute phase difference (MAD), phase difference standard deviation (PSD), signal-to-noise ratio (SNR), etc.) using a statistically significant imagery database; statistics and distributions of image quality features vs. gapping pattern parameters will be obtained from test bed studies. SSCI will demonstrate algorithm performance using previously collected SAR phase-history data; if SAR data containing real data-gaps is unavailable, equivalent data will be formed from real, non-gapped phase-history data and used in the demo. If previously collected SAR data containing real data-gaps is unavailable, SSCI proposes to subcontract with Raytheon Missile Systems of Tucson, AZ to obtain appropriate airborne data for a demonstration using gapped phase-history data. BENEFIT: One important advance in the development of modern airborne radar systems is the utilization of active array antennas which allow the radar to accommodate multiple modes for search, track, SAR imaging, etc. Many modes may compete for radar resources, resulting in severe timeline demands due to multi-mode operational requirements. The radar may not be able to dedicate an uninterrupted period of time required for SAR data collection, thus it may be necessary to interrupt the SAR data collection randomly or periodically to perform other radar modes. Such interruptions will leave data-gaps in SAR phase-history data which can significantly degrade the quality of the resulting SAR imagery. SSCI"s approach to SAR image reconstruction from gapped phase-history data will provide the user community with very good quality complex SAR imagery and the resulting imagery may be utilized for advanced exploitation modes such as SAR change detection (coherent and non-coherent), CFAR target detection, target recognition, interferometric SAR, etc. SSCI"s imaging approach works against temporal and/or frequency gaps, including periodic and randomly located phase-history gapping patterns. The utility of military and civilian SAR imaging radars will be greatly enhanced using SSCI"s"state-of-the-art"image-reconstruction algorithm for mitigating interruptions in SAR phase-history data.