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NIO’s Autonomous Vertical Profiler successfully tested to 200m in the Arabian Sea
The Autonomous Vertical Profiler (AVP) is a patented (US Patent #6,786,087) technology development of the Marine Instrumentation Group at the National Institute of Oceanography in Goa. By design, the AVP floats vertically on the sea surface, and when in motion it is propelled in a downward direction by a brushless underwater motor run at a constant speed. As safety measures, an echo sounder is mounted on its nose cone to detect the seabed and it is trimmed to make it lightly buoyant so as to ascend without propulsion after a dive. The profiler carries wet sensors of salinity, temperature,
chlorophyll-a, turbidity, and Dissolved Oxygen (DO). On breaking sea surface, the AVP transmits acquired high resolution (< 10cm) time stamped sensor profiles with its GPS coordinates over a high speed RF (Radio Frequency) link to users in a nearby ship/trawler or by satellite modem to a shore laboratory at NIO, Goa. A Graphical User Interface (GUI) enables the laptop user to check system health, sensor values and to configure a mission for single dives or for multiple unsupervised dives that offer adequate statistics on the variability of profile shape. The AVP is attached to a thin nylon tether that ensures recovery, but is loose enough to decouple it from ship or platform movements. The profiler has important applications in Environmental Monitoring of Coastal waters and in related Impact Assessment studies. Apart from extensive use in coastal waters, it has been used without changes in estuaries, fresh water reservoirs and dams for rapid time series profiling of these water bodies. The technology development team comprised Elgar Desa (Project Leader), R. Madhan, G. Navelkar, N. Dabholkar, S. Prabhudesai, Pramod Maurya, A. Mascarenhas and S. Afzulpurkar, and was funded by the Ministry of Communications and Information Technology, New Delhi.
Deep water tests and anoxia at 200m
The AVP was tested to its maximum designed depth of 200m in the shelf waters of the Arabian sea during cruise SSK 009 on
CRV Sindhu Sankalp
(see photograph). Multiple dives to 200m were made on the 12 Dec 2010 at Lat N 15 deg 9.59' , Long E 72 deg 57.10 '. As a spin off to the tests, the AVP detected anoxia to ~1 µM at depths close to 200m. This was confirmed by chemical analysis of DO water sample analysis. Anoxia detected as late as mid-December is unexpected and at locations well before the shelf break.
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