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Sunday, 23 January 2011

Yellow Submarines

Over the last two days quite some time was spent testing the Automated Underwater Vehicles. They are transported in the back of a van - in the photo you can see Rob Littlefield from the Woods Hole Oceanographic Institution preparing one of them for a trial run. The two AUVs each carry a different type of scanner that measures characteristics of the lake floor:
  •  A multibeam scanner - this creates a detailed 3D topographical (bathymetric) map of the lake bed.
  • A sidescanner - this technology uses acoustic (sound) signals to gather information about the hardness or softness of the lake floor sediments. Lava, mud or coarse boulders will give different signals, and so some idea of the geology of the lake floor can be gleaned.
The second photo shows Amy Kukulya, from WHOI making adjustments to one of the AUVs on Rotomahana lake shore.
Different sensors on the AUVs take other readings. If you think about it you will soon see how they all combine help to detect mineral rich, hot, hydrothermal vents:
  • Temperature
  • pH (acidity or alkalinity) 
  • Eh - this is the oxygen reduction potential of the water, where a high reading means that it has been introduced into the lake recently.
  • Turbidity - this uses a strobe light and measures the amount of reflection, indicating the density of particles in the water.
  • Conductivity - this depends on the amount of dissolved salt, which is also a feature of hydrothermal fluids.

Other sensors on the AUVs are there to help with navigation. This is a highly technical subject in itself, and makes it possible for the controller to have real-time information and remote control of the speed, direction and depth of the AUV. Amy deals with all this remotely from her computer in the back of the van. All the information she needs is at her fingertips...

The photos show that the weather has been pretty wet over the last two days, but some testing was done on the lake yesterday... and also in the hotel today:










Some of the guests were a bit surprised to see a torpedo like vessel in the swimming pool. One of the scanners wasn't quite behaving, until some of the settings were checked. This adds up to a very expensive way of finding out that the water depth was about 2 metres.

Everything is now set for work to begin.



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