Researchers sometimes need current profilers with a range of up to 400 meters on their vessels, if they are performing tasks such as upper ocean boundary layer studies. But while some instruments already on the market work at that range, they tend to be available only as costly, permanent installations.
Nortek has tackled that issue by developing a vessel-mounted Acoustic Doppler Current Profiler (ADCP) with a range close to 400 meters, suitable for use on ships, which aims to be both easy to install and use. This represents a step up in regard to range when compared to Nortek’s Signature VM Coastal system, which uses the Signature500 ADCP with a 70-metre range.
The new Signature VM Ocean is based on the 100 kHz Signature100, which allows measurement using cells of between 4 meters and 15 meters. In broadband mode it is highly accurate and can potentially reach 400 meters. Using it in narrowband mode extends the range, but precision is slightly reduced. This solution can be installed permanently under a vessel or be mounted in an over-the-side frame. The Signature VM Ocean can also be used in stationary conditions, for example on a buoy or in a bottom frame.
The instrument comes with bottom-tracking capability, as would be expected, but it also incorporates an integrated high-quality echosounder. This offers narrowband echo profiles at both 70 kHz and 120 kHz. There is also a wideband echosounder in the 70–120 kHz range that can be used for biomass measurements.
This integrated approach will be welcomed by scientists seeking all these capabilities, for example those carrying out fisheries research. Existing solutions generally involve combining separate echosounders and current profilers, usually sourced from different manufacturers. For these setups, installation can be complicated and time-consuming, as is the process of synchronizing the ADCP and echosounder to avoid the risk of acoustic interference.
As the Signature VM Ocean incorporates bottom tracking, current profiling and echosounding in one instrument, installation is simple and valuable time is saved on synchronization.
The system comes in Nortek’s now-familiar VM package, which includes a connection box, small computer, cable and GNSS navigational equipment that provides positioning, heading and time synchronization.
Accurate and robust: The Signature VM Ocean is suitable for use on larger vessels. The Signature VM Ocean can be used to study currents and biomass, for example krill, in the epipelagic layer of the ocean.
The Signature VM Ocean can be used on research vessels to measure currents and detailed echosounder profiles to study thermoclines and internal waves in the ocean.