A towed 75 kHz ADCP for operational deepwater current surveys

This paper describes the development of a towed acoustic Doppler current profiler (ADCP) system that is used to support operational monitoring of deepwater currents. The towed body configuration provides a quiet and stable sensor platform that can be readily relocated and deployed from different vessels. High-frequency ADCPs are used in towed bodies for several shallow water applications. This towfish system is unique because it employs a 75 kHz RDI Long Ranger ADCP packaged in a large Endeco/YSI type 850 V-Fin. The towfish is 1.3 × 1.4 × 0.7 meters and weighs 185 kg in air. The towfish, winch and electronics are housed in a customized container that allows for a single point lift for loading and a 2.5 by 3.5 meter footprint on deck. In 2004, the towfish was used operationally in the Gulf of Mexico to survey upper ocean currents. The surveys were successful with only minor setbacks. The system calibrations were found to be very robust and stable. The towfish was deployed at nominally 20 meters depth with tow speeds of 1 to 3 m/s. The ADCP provided continuous along-track profiles with good data down to the instrument´s maximum range of 500 meters. Raw data were telemetered to shore for processing and integration with satellite imagery and other in situ observations to provide a real-time synoptic analysis.