Integration and Testing of a Low-Profile Hydrophone Array with REMUS 100 AUV for Seabed Characterization and Marine Mammal Detection Application

Results from integration and testing of a digital thin line hydrophone array (DTLA) on a REMUS-100 Autonomous Underwater Vehicle (AUV) platform equipped with a compact sound source are presented. The objective of this work was to evaluate the usefulness of the integrated AUV acoustical technology for seabed characterization and marine mammal detection applications. Initial tests were carried out in Buzzards Bay and followed by a field experiment at the New England Mud Patch. Analysis of depth and heading sensor data showed that the AUV and the array were moving along a spiral trajectory with a slow rotating speed and a small oscillating amplitude. Nevertheless, arrival times of an array element localisation signal from the AUV-based acoustic source indicated that the array was reasonably straight, and array beamforming can be carried out. A separate signal received on the array from the same acoustic source, but used for seabed characterisation application, showed distinct arrival structure for direct, bottom reflected and surface reflected signals, which enabled estimation of the local seabed reflectivity at the AUV locations. In addition, a long-range Bayesian geoacoustic inversion was conducted using an impulsive signal originated from a combustive sound source at a distance and received on the AUV towed array. Some results from the data analysed with respect to seabed characterisation and marine mammal detection are also presented in this paper.