At-sea measurements with an Autonomous Vehicle Towed Array System, Avta

An autonomous vehicle towed array, Avta, system has been developed and demonstrated in several at sea experiments that show a small autonomous vehicle is capable of towing the array in a steady and stable configuration sufficient for coherent-synthetic-aperture processing. Calculated transmission loss compared well with measured transmission loss using this system and vehicle measured non-acoustic data i.e. currents, bathymetry, sound speed and range. Syntheticaperture-Hankel transformation of complex pressure as a function of range, was found to estimate the modal functions that characterize the waveguide. The limits of coherent processing are estimated and indicate sufficient coherence in the shallow water multi-path environment to form a reasonable narrow band and broadband synthetic aperture. Conventional and Kalman filter tracking techniques are applied to the broad band radiated noise of surface ship showing that a passive synthetic aperture can successfully be used to track ships.