SIGNALS, SIGNAL-PROCESSING, AND GENERAL RESULTS

Acoustic path lengths in the Heard Island Feasibility Test ranged from under 1 Mm to 18 Mm (1 Mm is 1000 km). The signal set consisted of th ree basic waveforms: cw, pentaline, and M-sequence-modulated carrier. This set offered the opportunity for successful measurements given the large uncertainty in prior estimates of propagation loss, stability, and arrival spread. Receivers ranged from simple sonobuoy systems to e laborate horizontal and vertical arrays. International collaborators a cquired data at a variety of sites worldwide. The resulting data has b een collected and subjected to a summary form of frequency domain proc essing. Variations in the recorded spectral phases are largely the res ult of nonuniformity in the speed of the source ship as determined by GPS comparison. Time domain processing has shown that at all ranges th e receptions exhibit exceptional stability.