ASA 124th Meeting New Orleans 1992 October

1pUW4. Acoustic telemetry of RDI Doppler current meter data---A real time acoustic link.

John Duchesney

Datasonics, Inc., P.O. Box 8, Cataumet, MA 02534

Steve Chappell

Univ. of New Hampshire

Neal Pettigrew

Univ. of Maine

James Sprenke


Datasonics has developed and tested a two-way acoustic telemetry link with software/firmware for command, control, and recovery of data from an (RDI) acoustic Doppler current profiler (ADCP) instrument. In operation, the acoustic link is quasitransparent to the system operator. Standard ADCP user command protocol allows PC-generated commands to be buffered and transmitted from a surface acoustic modem to a subsurface modem, which is connected by RS-232 interface cable to the ADCP. The acoustic down link command signals are reformatted in the subsurface modem and passed on to the ADCP. Data are transmitted over the up-link in 4096-byte packets at a data rate of 1200 bits/s. The self-contained subsurface acoustic telemetry modem (ATM) is housed in an aluminum pressure housing 5 in. o.d.x33 in. long. Connectors are provided for RS-422 I/O to the ADCP and for external power input for long-term in situ deployments. A choice of directional or omni directional acoustic transducers is available. The system was tested in the Piscatagua River in Portsmouth, NH and will be installed in Tampa Bay as part of NOAA's PORTS program, which offers shipping traffic access to current profiler data in near real time. The operating software protocol will be discussed and results from both the New Hampshire tests and Tampa Bay operations will be presented.