Coherent Multi-Static Active Sonar LRT

Multistatic sonar technologies are emerging as an important strategy for addressing passive ASW sonar-performance shortfalls. Multistatic operations can potentially improve ASW effectiveness in challenging shallow-water environments while allowing critical assets to remain acoustically covert or at a safe standoff distance. The Navy uses multistatic acoustic sensor systems with aircraft and surface ships, in a networked-centric ASW search and surveillance missions. Current incoherent systems suffer from high false alarm rates when operating in shallow water and potentially alert the target by using explosive sources. A method of reducing false alarms and not unnecessarily alerting our adversaries is needed. Coherent active sonar systems offer greater duty cycles, are not confused with weapons deployment when transmitting, and enable Doppler processing. The combination of higher duty cycles and controllable waveforms hold the potential for reducing false alarms. SSC and its teammate, Metron Inc., proposes to utilize Likelihood Ratio Tracking (LRT) to optimally combine multiple echoes, detect and track multiple targets using low signal to noise (SNR) threshold detections to form consistent target tracks over space and time. Extensions to LRT using Doppler information will be developed. This technique has been used successfully in incoherent multistatic active sonar systems and in passive sonar.