Overview of the SACLANTCEN family of trawl-resistant ADCP: evolution from self-recording to real-time profiler configuration

Recently there has been an increased demand for shallow-water current measurements, as a result of both military and environmental interest in littoral water activity. This has accelerated the technological evolution of Acoustic Doppler Current Profilers (ADCP) and has broadened the market. Long term (several months) deployments of ADCPs in heavily fished coastal waters are now relatively common. This paper describes the work conducted at SACLANT Undersea Research Centre (SACLANTCEN) since the 90s, in the field of trawl-safe ADCP platforms. This includes both the enhanced Barny Sentinel model developed at SACLANTCEN in collaboration with the US Naval Research Laboratory, Stennis Space Centre, and its more recent evolution into a Shallow-water Environmental Profiler in Trawl-safe Real-time configuration (SEPTR). All these platforms have a design that allows recovery by releasing the ballast, even if the platform is overturned as a result of trawling. Several of these units have been successfully deployed for two periods of nearly one year in total, by NRL in the Korea Strait, an area of intense fishing activity. The SEPTR system is a further evolution of the Barny Sentinel ADCP bottom platform, in that it adds an automated water column profiler, additional sensors, and two-way communication at regular intervals. It is intended for 3-6 month deployments in areas where water column instruments are at risk from fishing trawlers, but with real-time data return and control via two-way satellite communication. SEPTR includes a micro-controller based bottom platform which houses an ADCP, wave/tide gauge, ambient noise sensor array, and water column profiler buoy system. The profiler performs autonomous vertical profiling of CTD within the water column at depths down to 100.m. Recovery of the entire system is accomplished through either radio or acoustic communication with the profiler in order to release a messenger buoy. Two-way communication of data, position and control allows profile results to be returned in near-real time, and operational commands together with profile schedules to be sent to multiple profiler instruments. Project status and future plans are presented