Passive localization in range-rate of shallow-water moving targets, by sequential importance sampling

We examine the problem of passive localization of moving targets in shallow-water environments. In contrast with standard Matched Field Processing approaches, we localize targets in range-rate, rather than in range. This approach avoids smearing of target energy across range, and is more robust with respect to uncertainties about the ocean environment. In particular, it depends on the product of the channel-mode horizontal wave numbers and the differential distance traveled in a sampling interval, rather than the horizontal wave numbers and baseline distance to the sensor array. Thus it is less sensitive to errors in specifying the wavenumbers. The technique assumes some target dynamics and physics of the channel modes to hypothesize candidate sequences of mode coefficients. We evaluate the likelihood in range-rate and depth, updating it with a recursive Bayesian state-space model for the mode coefficients. To update the likelihood we employ a method of sequential importance sampling (SIS).