Preparing the BBOBS

Friday and Saturday were dedicated to preparing the seismometers so that they could be deployed as soon as we arrived in the study area on Saturday night. The BBOBS, or BroadBand Ocean-Bottom Seismometer, will allow us, with the help of pressure sensors and a current meter, to measure the deformability of the oceanic crust and to image the magma lenses below the surface.

Unpacking the seismometers and their floats.

After slipping weights under the floats, the seismometers must be attached to the arms that will hold them during the dive. They will release themselves on the ground.

Let’s go for the checklist! Simon and Milena check that they can communicate with the OBS, so that they can trigger the release systems, which must be checked and armed. In a week’s time, they will give them an electric current: the clamps that hold the floats to the weights will open to release the OBS.

The preparation of OBS is a lot of screwing, unscrewing, screwing again… And a few questions (where do these rings go???). Fortunately we have arms, especially when we discover that the electric screwdriver is still in Champs-sur-Marne… and that a small mistake in the assembly will force Alexandre, Rémi, Kristel, Manon and Milena to disassemble (and reassemble) all the arms!

Meanwhile, Antoine, Jean-Arthur and Valentine take care of the pressure sensors and the current meter. Walk, calibration, launch of the acquisition. And… Would JAO take up geochemistry?

His imagination and a lot of elbow grease allowed Antoine to fix the sensors (a large current meter and a small pressure sensor). But finally, a few hours before the dive, we change option!

8 pm. Everyone is ready!

Midnight. Launching of the first BBOBS by Lénaïg, Yannick and Adrien sailors of Pourquoi Pas ?

The first shift begins. Javier writes everything down. While Simon and Milena programme the acquisition of the following OBS…