Adaptive Track Detection for Multi-Static Active Sonar Systems

Multi-static active sonar systems detect contacts of interest by transmitting coherent waveforms and detecting the echoes on one or more receiving sensors. When a target of interest is in a region where its echoes are detectable by more than one receiver it can, in general, be declared sooner by combining the measurements from all sensors. The track detection schemes used in active sonar systems are often based on the Wald Sequential Probability Ratio Test (SPRT) and take as input the amplitudes of the target echoes associated to the track and where the statistical models for the amplitude of a target echo usually depend on a signal-to-noise ratio (SNR) parameter. The Multi-Static Adaptive Track Detector (MSATD) is an SPRT based track detection scheme that uses estimates of target aspect derived from track state estimates and a model of bi-static target strength to adapt the parameters in the distribution for target echo amplitude. Essentially, the SUM detector is modified to use different values for SNR parameter at each sensor. The SNR parameters are determined using a model of bistatic target strength and estimates of the target aspect observed by each sensor computed from the current track state estimate. The theoretical improvement in system track detection performance (i.e., probability of detection and latency) afforded by the proposed method is also presented; theoretically exact expressions for probability of detection and latency are evaluated numerically for all three track detection schemes for a system of one source and two receivers