TOMOGRAPHY DETAILS

Five 200-Hz transceiver moorings (T1 to T5), each equipped with a sound source and a 5-element vertical hydrophone array were deployed about 1100 m depth over a 1000 km scale domain centered at 33° N, 149° E; the five-mooring array produced 10 horizontal connecting paths.

Each mooring is equipped with a surface buoy for Global Positioning System timekeeping and real-time data telemetry, so that the inverse analyses of the acoustic travel time can be done in parallel with sound transmission and reception.

All of the transceivers were placed on TOPEX/POSEIDON (T/P) satellite altimeter ground tracks. Paths T2-T5 and T3-T4 were put along the descending T/P ground tracks p238 and p136, respectively, to simplify the comparison of the acoustic tomographic data the T/P altimeter data.

The sound transmissions occurred every 3 hours in August and every 6 hours in July and September within a 2-hour interval relaying around the five moorings.

The mooring motion was tracked using local long baseline acoustic navigation nets.

Transceiver position uncertainties were estimated to be approximately 2 meters, corresponding to a few milliseconds uncertainty of acoustic travel time.