Thursday, February 12, 2009

Day 20

Yesterday, the Norwegian team started deploying their moorings. These moorings are more difficult to deploy than the SASSI moorings, because they are "anchor-first", which means the 500-600 kg anchor is deployed first so the line is always under high tension. The first mooring went well. But during the second mooring deployment, the line suddenly broke, sending the instruments already attached to it to the bottom, lost forever ! Big disappointment and frustration... The mooring was redesigned for an anchor-last deployment, and shortened with the remaining instruments. Since they had enough people helping for the deployment, I took pictures to document how a mooring deployment proceeds.

In an anchor-last deployment, the first equipment to go overboard are the buoyancy devices : glass spheres protected within plastic shells (in red in the picture). Then follows the first instrument : an ADCP (Acoustic Doppler Current Profiler, in yellow in the picture). Helge is pulling the glass spheres out, and Charlie is giving hand signs to the upper winch operator who controls the position of the block through which the line goes.

The glass spheres drift away from the ship, pulling the line out. This is the major inconvenient for anchor-last deployments in these conditions : you need a vast area of ice-free water !

Then various instruments are attached to the line at specific lengths, corresponding to specific depths once the anchor is sunk to the bottom.
Here the instrument is a CTD (Conductivity-Temperature-Depth) sensor.

Ilker in a remake of "The Matrix" !

Keith, the Principal Investigator for the cruise, driving the lower winch, which controls the speed of the line. His casual stance is in fact a way to put his weight on the lever, which is very hard to move and maintain in a fixed position. Given the fact that you have to hold the position for long periods of time when deploying thousands of meters of line at a speed of 1-2 meters per minute, it is a quite tiring job. I was driving this winch for the SASSI deployment.

Watching the line running out between two instruments...

A current meter that works like an anemometer is being attached to the line...

... before going out.
Ilker, the Principal Investigator for these moorings, is watching that everything is going according to plans.

Finally, the anchor, an old train wheel, is lifted up from the deck and held over the water, with a special device to release it when the ship is exactly over the desired location.

Ready to go !

With the big splash, the deployment ends successfully, and everyone cheers and can relax, before the next deployment...

1 comment:

  1. As tu reçu mon coup par email ?
    j'espere que les baleines ne vous ont pas fait chavirer ! :-)