DISTRIBUTED VERTICAL LINE ARRAY (DVLA) ACOUSTIC RECEIVER

Abstract: A Distributed Vertical Line Array (DVLA) receiver able to span the full water column in water up to 6000 m deep has been developed to allow both modal and ray-based analyses 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) the availability of flash memory modules that can store several gigabytes of data and be located in a small pressure case at each hydrophone, making it unnecessary to transfer data from the hydrophones to the central controllers for storage, and (ii) inductive modems that allow low-bandwidth communication for command, control, and time synchronization between the D-STAR controllers and the Hydrophone Modules over standard oceanographic mooring wire. The DVLA is modular, consisting of subarrays with a nominal length of 1000 m, each of which has one D-STAR controller and up to 99 Hydrophone Modules. A D-STAR controller is shackled in-line at the top of each subarray. The Hydrophone Modules are clamped to the mooring wire at the time of deployment, making the DVLA readily configurable for different experiments. The D-STAR clocks are synchronized acoustically, avoiding electrical interconnections. The DVLA is navigated using acoustic transponders positioned on the seafloor around the mooring. The Hydrophone Modules make precision temperature measurements throughout the time that the DVLA is deployed, in order to provide the sound-speed profiles needed for beamforming