Garry J. Heard
Defence Res. Establishment Pacific, Bldg. 199, FMO Esquimalt, Victoria, BC V0S 1B0, Canada
JASCO Res. Ltd., Sidney, BC V8L 3S1, Canada
Canada was one of nine participating countries in the Heard Island Feasibility Test (HIFT) and had two towed-array receivers operating, one in the Pacific and one in the Atlantic. Due to the extremely long propagation paths the Canadian data were found to have relatively low signal-to-noise ratios that complicated the M-sequence time-compression correlation processing. An analysis was carried out to determine if time-compression processing of the data was possible with the low signal-to-noise ratio data available. A means of removing Doppler variations from the data based on phase tracking the heterodyned baseband signal was developed and applied to several of the stronger HIFT receptions. Useful correlation results were obtained using this technique. Initial estimates of the travel time differences for the dominant acoustic arrivals were obtained from the correlations.