Passive range estimation of an underwater maneuvering target

This paper examines the problem of adaptively tracking, in the horizontal ocean plane, an underwater maneuvering target using passive, time delay measurements. The target is free to make large scale random changes in velocity and bearing at times that are unknown to the observer. Tracking is accomplished by utilizing the basic linearized polar or "spherical" model of target and observer motion previously developed for radar tracking of airborne maneuvering vehicles[1]. The addition of a nonlinear system block to the tracking system leads to a partial decoupling of both bearing and polar range estimators which not only reduces computational burden, but also significantly reduces any tendency toward tracking divergence. A modified method to obtain closed-form expressions for the measurement error statistics is presented which replaces conventional extensive off-line simulation procedures. Finally, test results are shown which validate the elimination of all extended Kalman filters in the measurement processing. This makes the passive tracking system very "robust" with respect to convergence characteristics in the presence of adverse target maneuvers.