An experimental test of end-fire synthetic aperture sonar for sediment acoustics studies

Abstract

Seafloor sediment acoustic returns are comprised of scattering from both the interface and sediment volume. At low-frequencies, volume scattering is often the dominant mechanism; however, direct measurements of this component have rarely been made, due to interface roughness biasing caused by large beamwidths. End-fire synthetic aperture sonar (SAS) can achieve narrower beamwidths by coherently combining multiple acoustic returns as a vertically oriented transmitter and/or receiver is moved towards the seafloor. Beam pattern simulations suggest end-fire SAS can reduce the beamwidth of a sonar by a factor of 6 with an array length of 100 wavelengths. Achieving these gains is dependent on the ability to resolve relative sonar motion to at least an eighth of a wavelength. This talk will present results from an end-fire SAS field trial. Results will include an analysis of beamwidth gains achieved during the end-fire SAS field test and methods to improve these gains by using the scattered field to refine sonar positions.