64PE367 - Diary 3

Deployment procedure When the KM3NeT will be built, the optical modules will be lowered once to the sea-bottom where they will stay for at least 15 years. However, during the Pelagia-test-cruise they stay at the bottom for a few hours or a day. They need to be brought back to the surface for re-use. This makes the deployment operation much more complicated than the future telescope-construction. It is because one cannot simply release the lines with glass spheres, as the spheres will break into each-other at the surface. Thus, another mooring is anchored nearby (1.4 km away). The weights are connected with a heavy steel cable (see the diagram).

To deploy, first the orange buoy is put overboard, followed by the 1000 m line to the right. The first weight is attached between the line and the bottom cable. After spooling the 1400 m cable, the fully loaded LOM is attached and lowered to the bottom. A tricky operation, especially when the LOM touches the bottom and the cable has to be released quickly.
So far after 4 days, we have completed 3 deployments and all went as planned. The third one this morning was just at the limit, as we deployed under force 7 winds. There are few ships and crews who can do this operation under such conditions, which once more shows how well it is done from the Pelagia!