Motion compensation feasibility for high resolution synthetic aperture sonar

Aperture synthesis is a technique for obtaining very fine cross-range resolution for side-looking radars or sonars. High performance synthetic aperture radars (SARs) are now in routine use, both on airborne and space-based platforms. However, despite its conceptual origin coinciding with SAR, synthetic aperture sonar (SAS) has received only limited demonstration, and none of these has approached the limits of resolution and range permitted by the underwater environment (e.g. 2 in resolution over a 2000 ft swath). This is largely a consequence of the more stringent motion compensation requirements for SAS relative to SAR, and the severe phase fluctuations induced by the underwater medium. As the performance of SARs continues to be improved, processing and autofocusing algorithms have been developed that promise to alleviate the difficulties of SAS. Using a high fidelity, end-to-end simulation, the authors demonstrate that available SAR autofocusing algorithms can compensate the residual motion compensation errors and medium-induced phase errors that are inevitable for high performance SAS