A Low-Frequency Sonar for Sensor-Adaptive, Multi-Static, Detection and Classification of Underwater Targets with AUVs

The Generic Ocean Array Technology Sonar (GOATS) Joint Research Program is currently exploring the development of sensor-adaptive autonomous underwater vehicle (AUV) technology specifically directed toward rapid environmental assessment and mine countermeasures in coastal environments. As part of the effort, MIT is developing the GOATS multi-static sonar concept with the goal of being able to detect and classify targets on and within the seabed in very shallow water. To support this project, a high performance, multi-channel sonar was developed as a payload for the Odyssey-III class AUVs used by MIT and a number of other institutions. This sonar payload is capable of low/mid frequency target insonification, real-time processing of 16 array channels and communication with the main vehicle computer for realtime, adaptive mission coordination. The sonar payload also has the capability to time synchronize with the payloads on other AUVs with microsecond accuracy and the ability to maintain tight time synchronization while all vehicles are underwater, thereby enabling multi-static processing of sonar returns. The entire sonar payload was designed and implemented as a virtual sensor with respect to the main vehicle computer. Results from two major international experiments are presented in which both the time synchronization capabilities and the online detection capabilities of the sonar were tested and in which we believe the first ever online target detections were achieved with a system of this type.