Passive Acoustic Signal Processing at Low Frequency With a 3-D Acoustic Vector Sensor Hosted on a Buoyancy Glider

Abstract

This article deals with the detection of low-frequency noise sources and the estimation of their direction of arrivals using an acoustic vector sensor hosted on a buoyancy Slocum glider. The sensor used is a 3-D directional hydrophone capable of acquiring both the acoustic pressure and the components of the particle velocity vector. This article presents experimental results with data collected at sea and describes the signal processing chain, including detection, direction of arrival, and clustering. The vehicle is equipped with a modem and is supported by an ultrashort baseline (USBL) located on a mother ship or gateway to achieve the navigational accuracy required for correct target localization. The surface vessel localizes the glider via the USBL and then transmits position fixes, which are used by the underwater vehicle to reset the drift error of its navigation filter. The results discussed in this article demonstrate two important achievements, i.e., an underwater glider can produce accurate bearing estimates on a target and the feasibility of the integration of an acoustic modem and a USBL positioning system on a glider. The results obtained open up the possibility of using multiple autonomous sensorized gliders integrated in intelligent surveillance robotic networks.