Broadband synthetic aperture chirp reflection profiling

Abstract

A newly developed towed chirp subbottom profiler transmits FM pulses with a bandwidth of three octaves to generate high resolution reflection profiles of the seabed. The broad bandwidth of the pulses, generated with two arrays of piston sources, produces the temporal resolution needed for resolving fine sediment layering. A 40 channel horizontal hydrophone array, embedded in vehicle wings, provides the acoustic aperture for enhancing the across track resolution of subsurface features and reducing sediment scattering noise. After application of a matched filter, synthetic aperture processing of hydrophone data generates a large aperture along the track of the sonar vehicle thereby improving along track image resolution and obtaining a further reduction in scattering noise. The reductions in backscattering from sediments yield imagery with improved subsurface penetration. The reflection profiles are stacked envelopes of coherently summed data formed by time domain focusing on planar surfaces oriented over a...