Localisation Performance of Passive Sonar for Self Protection Against Fast Craft

Assets at sea are vulnerable to attacks from fast craft relying on the effect of surprise. These threats are not necessarily stealthy but leave a very limited time of reaction to the platform at risk. Early detection of the approaching vessel provides an opportunity for the attacked ship to react in time. Accurate localisation of the threat helps deciding for the best reaction and reducing false alarms. Localisation of such threats is often performed using sparse hydrophone arrays. Reliable passive localisation is challenging as the precision is determined by geometry and sensor positioning accuracy. In this paper, we present a localisation technique of time delay estimates integration using a Maximum Likelihood Estimator that estimates the position and speed of a moving target. Using the Fisher Information Matrix and the Cramèr Rao Lower Bound, we provide performance indicators for different array and measurement configurations. We further investigate the influence of hydrophone position uncertainty on the localisation performance. The results of this work can be used to assess the applicability of this method to locate fast moving craft and optimise sensor configurations to obtain reliable localisation