Detection of ship wakes using an airborne magnetic transducer

Wakes induced by the motion of vessels may extend for tens of kilometers and exist for hours under certain conditions in the open sea. This provides a useful feature for long-range ship detection. The authors present a method for passively detecting a ship wake using measurements obtained by an airborne SQUID magnetic transducer that measures the first order gradients of the magnetic signature induced by the wake. Analytical formulas for wake magnetic gradients are derived to provide guidelines for using the airborne detector. They also derive bounds on the probability of wake detection for cross correlation and square-law detectors, which can be used to predict the expected performance. Numerical examples are used to demonstrate the applicability of their results.