Distributed vertical line array receiver.

Abstract

A distributed vertical line array (DVLA) receiver able to span the water column in water up to 6000 m deep has been developed to allow both modal and ray-based analyzes of acoustic propagation. The DVLA is made up of distributed, self-recording hydrophones with timing and scheduling provided by a small number of central controllers, called D-STARs. The enabling technologies for this approach are (i) flash memory modules that can store gigabytes of data in a small pressure case at each hydrophone and (ii) inductive modems that allow low-bandwidth communication between the D-STAR controllers and the hydrophone modules over standard oceanographic mooring wire for control and time synchronization. The DVLA consists of sub-arrays with a nominal length of 1000 m. The hydrophone modules are clamped to the mooring wire during deployment, making the DVLA readily configurable. It is navigated using acoustic transponders on the seafloor. The hydrophone modules make precision temperature measurements to provide the sound-speed profiles needed for beamforming. A DVLA consisting of two 1000-m sub-arrays, one spanning the sound-channel axis and the other spanning the surface conjugate depth, was successfully deployed in the Philippine Sea for 1 month during spring 2009. [Work supported by the Office of Naval Research.]