Effect of Element Failures on the Performance of Passive Towed Array Sonars

Abstract

Linear towed arrays are one of the principal methods of underwater target detection, especially at low frequencies. A typical towed array contains many hydrophones in a flexible tube towed several hundred meters behind the ship. A practical problem in towed arrays is hydrophone or channel failures. Failed channels impact the side lobe levels and increase the leakage from tow-ship noise. This significantly affects the achievable figure of merit of the system. It is necessary to achieve quantitative assessments of the performance degradation to decide on the future course of action for maintenance or repair. In this paper, we propose a method to quantitatively assess the performance degradation of the sonar due to element failures. This method is capable of suggesting the operational envelopes of the platform which will still give acceptable performance under failed conditions. Simulation results and an online performance monitoring scheme are proposed, which will give in situ information on the performance degradation and sonar health. The experimental results with a linear array towed at different speeds and the corresponding degradation experienced due to element failures are also evaluated and found to match with the predicted results.