Development of a gimbaled ADCP trawl-resistant bottom mount

A prototype gimbaled trawl-resistant bottom mount (TRBM) is under development at the Naval Oceanographic Office and Woods Hole Oceanographic Institution to facilitate nonintrusive acoustic Doppler current profiler (ADCP) current measurements in shallow seas and littoral waters that are subject to extensive fishing activity. The TRBM is capable of free-fall deployment from a surface vessel to its maximum operational depth of 600 m. The gimbaled 75-kHz ADCP transducer head provides automatic vertical signal alignment in the water column, while the TRBM is in situ. The recoverable instrument housing is located and released using a shipboard-mounted acoustic release command system to interrogate and release either of the dual acoustic releases located in the TRBM. Although the prototype unit was designed for the 75-kHz ADCP, the TRBM can be easily modified to accommodate 150- through 1200-kHz transducer heads to facilitate higher resolution measurements in shallow coastal waters and harbors