LAUSR

Multiple ocean vehicles, including both surface ships and unknown submerged vehicles, can be simultaneously monitored over instantaneous continental-shelf scale regions via passive ocean acoustic waveguide remote sensing (POAWRS) by employing a large-aperture densely sampled coherent hydrophone array system. Here, the approach is demonstrated for multiple merchant ships present in the Norwegian Sea in 2014. The sounds radiated underwater by ocean vehicles, dominated by narrowband tonals and cyclostationary signals, are detected in the beamformed spectrograms. Coherent beamforming of the receiver array data significantly enhances the signal-to-noise ratio of the ship-radiated signals enabling detection of ocean vehicles roughly two orders of magnitude more distant in range than a single hydrophone. The estimated bearing-time trajectory of a sequence of detections are employed to determine the horizontal location of each vehicle using the moving array triangulation technique. The estimated locations are ver...