Sensors and Moorings
Sensors and Moorings are responsible for a large range of instruments that are deployed in profiling, shallow towed or moored applications. Great care and attention to detail during preparation is essential to ensure the reliable and consistent operation of instrumentation that can be in the ocean for up to 24 months in the case of moored installations.
Sensors and Moorings technicians are responsible for the procurement, preparation, deployment, recovery, servicing, repair and calibration of instrumentation and equipment in the National Marine Equipment Pool and the RAPID programme. Additionally liaising with the international scientific community, designing equipment and moorings, and wherever possible incorporating new technologies to support science delivery are routine responsibilities of technicians.
Sensor and Moorings maintain a Calibration Laboratory facility which undertakes calibrations for Temperature, Conductivity and Pressure measurements for sensors housed in a variety of instruments.
The CTD (Conductivity, Temperature, Depth) platform is the workhorse of Sea Systems and is used on 90% of all cruises. Not only does it provide real-time, accurate and precise data from the water column up to 6000m deep, it has the ability to take up to 24 water samples at depths chosen by the operator.
As well as the C, T and D sensors, a CDT package carries instruments to measure turbidity (particulate concentration), fluorescence, oxygen concentration and an echosounder to measure distance from the seabed. A current profile is also logged using an Acoustic Dopler Current Profiler. Despite the frequent use, the sensors are calibrated frequently to meet international standards. Temperatures, for instance, are measured to 0.003ᵒC.
Special care must be taken when preparing moorings with a surface element as winter storms in the North Atlantic can generate waves over 25m in height. The design of the mooring takes into account not only these extreme weather conditions, but also sub surface currents that are acting on the ropes and wires reaching down to the seabed.
The data gathered is transmitted back to shore via satellite link, enabling real time analysis of a wide range of oceanographic parameters as well as monitoring meteorological events.
The Moving Vessel Profiler (MVP) allows near vertical profiles to be measured from a moving vessel, typically to 300m depth at a speed of 10 knots. Parameters measured include depth, temperature, conductivity (used to calculate salinity), oxygen concentration, chlorophyll concentration and light intensity.
The system is comprised of an electro mechanical winch system with a Kevlar conducting cable, the towfish carrying the instrumentation and the control and data acquisition elements which can display the data in real time. The system, while nominally autonomous, is very complex and requires regular maintenance and an engineering watch to be kept.
