Acoustic Seagliders in PhilSea10: Preliminary results

In November 2010, four acoustic Seagliders were deployed in the Northern Philippine Sea in the vicinity of an acoustic tomography array as part of the PhilSea10 project with the goal of characterizing this oceanographically complex and highly dynamic region. The gliders were flown between the moored transceivers of the pentagonal tomography array with a radius of approximately 330 km until their recovery in April 2011. During this mission they collected oceanographic and acoustic data in the upper 1000 m of the water column. Temperature, salinity, and pressure data collected by the Seagliders provide a time-evolving characterization of the sound-speed environment in the variable upper ocean between the transceivers. The gliders were also equipped with an integrated Acoustic Recorder System (ARS). The ARS was scheduled to record transmissions from the moored acoustic tomography sources, measuring the arrival structure between the various moorings in order to near-continuously map the arrival pattern as a function of range and depth. Spectrograms show the arriving linear frequency modulated signals from the sources, as well as other ocean sounds. With travel times determined from this data, we will determine whether, given the joint nature of the combined positioning/tomography problem, it is possible to use Seagliders equipped with an acoustic receiver as mobile nodes in the tomography array, thereby enhancing the resolution of the tomography system.