The effects of marine fouling on the performance of a single-point acoustic Doppler current sensor mounted on a TABS-II spar buoy

Following the successful results of an experiment conducted during June and July, 2000 to determine how a single-point, acoustic Doppler current sensor would perform on a TABS-II spar buoy, a second experiment was conducted to determine the effects of marine fouling on the sensor. The TABS-II spar buoy is one of two types of spar buoys used by the Geochemical and Environmental Research Group (GERG) to monitor and report near real-time surface currents, in support of oil spill response and trajectory modeling for the Texas General Land Office in Austin, Texas. An Aanderaa DCS3500R Doppler current sensor was mounted on a TABS-II spar buoy and moored at a location approximately 22 nmi southwest of Galveston, Texas in 19 in of water. The mooring remained in place from June 1 to December 15, 2000 during which time it reported hourly near-surface current components and temperature via satellite telephone to GERG´s office in College Station. On November 15, 2000 a second TABS-II spar buoy, equipped with a clean, calibrated, Marsh-McBirney, Inc., (MMI) Model 585 electromagnetic sensor, was deployed 200 in downcoast of the DCS3500R-equipped buoy. A 600-kHz RD Instruments directional-wave ADCP was mounted on the bottom between them in an upward-looking configuration. On November 15, 2000, prior to deployment of the MMI-equipped buoy and the ADCP wave meter, the DCS3500R-equipped buoy was recovered to remove marine growth from the hull and mooring. Barnacle growth on the DCS3500R was extensive, covering the entire sensor and cable