An AUV Mounted Vector-Sensor for Seismic Surveying

The innovative usage of robotic vehicles for seismic surveying where, in sharp contrast to classical solutions, acoustic sources and streamers are carried by Autonomous Surface and Underwater Vehicles (ASVs & AUVs), respectively poses significant scientific and technical challenges. Among these, is the requirement of reducing the streamers length to improve the maneuverability and endurance of the towing vehicles without compromising the resolution of bottom images. A possible approach to tackle this challenge is to use vector sensors (VS) that are both compact and have high spatial discrimination performance. Such a sensing device - known as the Dual Accelerometer Vector Sensor (DAVS) - was designed, developed and tested in the framework of the WiMUST project. This work describes the experimental setup adopted and analyzes the data acquired during engineering trials carried out at the Lisbon Oceanarium marina, in Portugal, with a sparker mounted on an ASV and a DAVS mounted on a companion AUV. The Oceanarium marina is a very shallow site where the direct, surface and bottom reflected arrivals overlap in time. The results show that DAVS data can be used to attenuate noise and undesired surface reflections, and separate bottom and surface arrivals. Therefore, they suggest that a few VS can achieve a performance similar to that of longer hydrophone streamers and be advantageous in challenging survey areas where the traditional seismic setup can not be adopted.