Critical distance and the performance of sensor array geometries

In antisubmarine warfare (ASW) an aircraft is often used to drop sonobuoys in a pattern to try to locate an enemy submarine. If a target is detected, it may be necessary to drop more sensors to improve the direction of arrival (DOA) resolution in the direction of the target. The authors analyse the two source case in detail and develop a critical distance definition that plays a major role in the resolution performance of an array. The critical distance leads to a solution to the problem of where to place the next sensor to achieve a desired level of resolution performance in the direction of the target