ASA 126th Meeting Denver 1993 October 4-8

4aUW5. Environmental source tracking using measured replica fields.

W. A. Kuperman Michael D. Collins John S. Perkins Laurie T. Fialkowski Timothy L. Krout

Naval Res. Lab., Washington, DC 20375

Lindsay Hall Ralph Marrett

Defence Scientific Establishment, Auckland, New Zealand

Lesley J. Kelly Ashley Larsson

Defence Science & Technology Organisation, Salisbury, SA, Australia

John A. Fawcett

Defence Research Establishment Pacific, Victoria, BC, Canada

Preliminary results will be presented for TESPEX (Test of Environmental Signal Processing Experiment), which was performed in May 1993 off the east coast of New Zealand in a region of three-dimensional bathymetry variations. This complex environment was exploited to minimize ambiguity in environmental source tracking with a single receiver [Collins et al., J. Acoust. Soc. Am. 90, 2366 (1991)]. To overcome limited knowledge of environmental parameters, the acoustic field was measured by a fixed array of receivers while a ship towing a source swept over a sector. The receivers were linked to a recently developed satellite telemetry buoy that transmitted time series to a centralized computer facility for real time analysis. Expensive ship time was traded off for cheap computation time by interpolating the acoustic field using a WKB representation that permits a sparse sampling in azimuth. The main computational task for the data basing involves solving a nonlinear optimization problem for the WKB amplitude and phase functions, which vary slowly with range and azimuth. TESPEX data have been used to perform environmental source tracking using replicas constructed from the acoustic field data base. [sup a)]Present address: Scripps Institution of Oceanography, La Jolla, CA 92093.