Greg Duckworth Kevin LePage Ted Farrell
Bolt Beranek and Newman, Inc., 70 Fawcett St., Cambridge, MA 02138
The ONR AEAS Program sponsored a low-frequency reverberation study program in the Central Arctic as part of the AREA-92 Exercise in March--April of 1992. The ZIRCON ice camp was the site of the monostatic and bistatic active sonar experiment with acoustic sources, a 256-channel billboard receive array, and real-time processing and display system. The reverberation data collected have been coherently processed between sequential pings to estimate the bearing, range, and radial velocity of ice scattering footprints of various range and bearing extents. Due to the highly repeatable nature of reverberation from the ice canopy, high source strength, and the gain of the receiver array, this processing is shown to be capable of unambiguously estimating the movement of these footprints over a 250-km-radius area to better than 10-m accuracy for transmissions as far apart as 4 h. Strain rate estimates using the technique agree with sparse GPS data in the area covered, and are shown to be well modeled by a simple three-parameter strain rate field. The details of the output from the processing also shed light on the fundamental acoustic propagation and backscatter processes themselves. [Work supported by ONR.]