Seismic Equipment: OBS Part 2 – Deployment!

Howdy! Last couple days have been very very exciting for the science crew. We have started deploying the equipment! At the time of writing, we have finished our first OBS transect (deployed, shot the air guns and collected the OBS) and finished deploying the OBS on the second OBS transect. We are now maneuvering the ship to shoot the second transect.

This post is the part 2 of the series on OBS equipment. I will be talking about the deployment of the OBS. This is a simple process but every step has to be done to perfection to ensure that the equipment records data and floats back to the surface. There are a series of steps that need to be taken before the OBS can be deployed. Peter and Dan from WHOI (Woods Hole Oceanographic Institute), have to go through a series of checklists to make sure the equipment work, from testing the lights (which will help in recovery) to seeing the measurements of the geophone and hydrophone. Once the equipment is tested, we wheel the OBS out to the deck to be lifted by a crane. When we reached our destination, the Bridge gives us the okay to start slowly lowering the OBS into the water. Once it touches the water, there is a clamp that is released and the OBS will float down to the sea floor. Then Peter and Dan check to see if the OBS is indeed falling or not. When it is confirmed that it is falling, they turn the acoustic transponder off and their job is done…for now. As mentioned previously, since we can’t control the OBS when it is in the water, we employ the “Pray and drop” approach to reach its destination on the sea floor. The OBS will take approximately 4 hours to fall to the sea floor and deploy the geophone. Then this process repeats for each OBS drop along the transect. The following are pictures taken during the deployment of the  OBS.

Gail and Dan looking at the computer as Peter troubleshoots the OBS. (photo: Stacey Worman)

Dan going through the checklist to make sure everything works. (photo: Akhil Amara)

Peter attaching the flag to the OBS. (photo: Akhil Amara)

Peter and Dan with the help of a deck hand move the OBS over the deck to slowly lower the equipment into the water. (photo: Akhil Amara)

Gail, Dan and I watching the readings to make sure the OBS is indeed falling to the sea floor. (photo: Stacey Worman)

 

That’s it for this post! Stay tuned for the final installment of the OBS equipment: Collecting the OBS!

 

Akhil Amara

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