Detection of ship wakes using an airborne magnetic transducer

Wakes induced by the motion of vessels may extend for tens of kilometers an d exist for hours under certain conditions in the open sea. This provides a useful feature for long-range ship detection. We present a method for pass ively detecting a ship wake using measurements obtained by an airborne SQUI D magnetic transducer that measures the first order gradients of the magnet ic signature induced by the wake. Analytical formulas for wake magnetic gra dients are derived to provide guidelines for using the airborne detector. W e also derive bounds on the probability of make detection for crosscorrelat ion and square-law detectors, which can be used to predict the expected per formance. Numerical examples are used to demonstrate the applicability of o ur results.