Synthetic Aperture for Surveillance Applications Using A Towed Array

This proposal addresses the use of synthetic aperture proceseing techniques in low resolution towed array eonar eyeteme for ASW applications. The proposed approach will apply theme techniques to enhance Gignal to noise and bearing resolution despite (a) uncertainties in the knowledge of the 9onar trajectory, (b) inaccurate estimates of the speed of sound as a function of depth, and (c) unknown target trajectories. Self-cohering (auto-focusing) techniques are used to adaptively compensate for the errors caused by deviation of the target and array trajectories from a linear path, and also for inaccuracies in the estimated speed of sound. A series of wideband pulsee are transmitted towardm the target area; the large bandwidth breakB up the ABM target into several range cells. Two self-cohering algorithms that have been successful in synthetic and inverse synthetic aperture radar, called the dominant scatterer algorithm and the 9patial correlation algorithm, are used to extract the corrections needed to compensate the errors from the measured echoes. The bearing coordinate of the image formed after applying the self-cohering corrections to the data will be ecaled and shifted if the target trajectory in not known. E9timatea of the target trajectory can be ueed to remove this distortion.