The Nordic WOCE travel-resistant ADCP system

In the Nordic WOCE programme 10 Acoustic Doppler Current Profilers (ADCPs) will be deployed between Greenland and Scotland. Three of these deployments will be in very heavily fished areas, and a special system has been developed to reduce the risk of interaction between the rig and fishing gear. The system consists of a buoyant instrument package and a protecting platform which will remain on the bottom. The instrument package is a stainless steel frame containing a 150 kHz RDI ADCP with a 90/spl deg/ adapter, an acoustic release, an ARGOS transmitter and sufficient flotation to give the instrument package a net buoyancy of 180 kg. The protecting platform has the form of a truncated pyramid with sides sloping 45/spl deg/ made of steel. During operation the instrument package is attached to the protecting frame by rods in the two ends around which the instrument package may rotate freely. If the system is turned upside down, the instrument package is designed to turn to an operational orientation and it can be released in this condition. To ensure acceptable tilt and stable bottom conditions a deployment frame has been developed with tiltmeter and video camera attached. A prototype of the system was deployed in October 1994.