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Down Wire Net Monitor

The RMT 25 is retrieved onto the deck of the James Clark Ross off South Georgia RMT25 - Rectangular Midwater Trawl  having a mouth area of 25 square metres. There are two nets that can be opened and closed underwater.

One of the activities of our marine biology cruises, on board RRS James Clark Ross, is sampling Krill and other zooplankton using scientific net systems such as the RMT, multinet or LHPR.

These all require remote control of their net closure systems. It is also desirable to log as much data about the environment the net is in at the moment of sampling. There is also a basic requirement to know what depth the net is at. Down wire net monitor computer screen

Before the James Clark Ross, this functionality was achieved with an acoustic net monitor system. The extremely low data bandwidth available, plus the unreliability of the net actuation led the Marine Life Sciences Division at BAS to seek an improved means of net control, with enhanced data collection capabilities.

 The James Clark Ross was built with a conducting (single conductor) tow cable and, subsequently, AME were approached to design and build a net monitor system. The prime requirements of the system were that it would be powered from the surface and transmit data in real time using the cable, as well as receiving commands for net closure.