A passive sonar system based on an autonomous underwater vehicle

Autonomous underwater vehicles (AUVs) are typically used to "actively" probe the ocean, using sensors that are mounted on a vehicle that moves through the water column. A more challenging task is to use an AUV to position a bottom-mounted stationary platform, such as a passive sonar that requires a large aperture. This paper describes the development of a passive sonar, which was mounted as a payload to the Ocean Explorer II, AUV developed at the Florida Atlantic University. The payload was designed so that the AUV could land on the seafloor and deploy the sonar. The passive sonar developed for this system can be used to measure and localize broadband sources that generate ambient noise in the coastal region. The sonar uses a sparse volume array of only six elements and a 2 m maximum dimension. With this array, it is possible to generate three-dimensional images consisting of thousands of independent pixels for any look direction or chosen image plane. This paper describes the ambient noise sonar and the variable buoyancy system used in deploying the array, and then presents some typical results obtained using the sonar.