Experimental testing of broadband decomposition of the time reversal operator (DORT) in shallow water

Abstract

Results are shown from the application of DORT to at-sea data taken in an area south of Hudson Canyon off the New Jersey coast during Spring 2004. A vertical source/receiver array with 64 hydrophones spanning the water column of 100-m depth was operated in 500-Hz bands between 500 and 3500 Hz. Sets of four, five, or six beams were transmitted at small angles from horizontal and the response from an echo repeater was recorded on 64 channels. The resulting data were analyzed using broadband DORT. Specific transmissions were used to quantify the degradation of coherence due to temporal variability of the source/receiver, environment, and echo repeater. The isolation in the singular vectors of the echo repeater using sets of independent source beams is comparable to that from the coherence tests. The singular spectrum of the noise field is compared with the expected results from that of a random matrix. Backpropagation images based on at-sea data and propagation using in situ XBT measurements are shown. [Work supported by ONR.]