After a ~48 hour hiatus from transponder deployments, we got back on track today (despite choppy waters), much to the excitement of the restless crew. We have had a productive day, with 4 MESH site transponder (-AF04, -AF05, -AF07, and -AF08) deployments. As we write this blog post, we are underway to recover a float pack before continuing with deployments (and eventually CTD casts) into the early hours of the morning.
In this post, we want to 'show you the ropes' for a transponder-float pack deployment-recovery sequence. The backbone of these operations (aside, of course, from the incredibly talented bosuns, deckhands, and technicians) is the sturdy, state-of-the-art hydraulic A-frame at the stern of the ship.
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| The A-frame, located at the stern of the ship, is the backbone of all overside handling operations. [PC: Yinchu Li]. |
The A-frame is the cornerstone of all overside handling operations, including our transponder-float pack deployments and retrievals. Once a transponder is configured for deployment, it is positioned below the A-frame to be secured, raised off the deck, and lowered into the ocean--a process that requires a lot of coordination, communication, and caution amongst the crew. In this process, the A-frame is rotated outboard, and the cross-beam rotates freely to accommodate the suspended load.
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| Transponder suspended from the A-frame and being lowered into the ocean. [PC: Behnaz Hosseini]. |
Immediately following the release of the transponder, the tethered float pack is positioned for deployment. In a similar fashion, the float pack is secured, raised off the deck, lowered into the ocean, and released.
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Float pack suspended from the A-frame and being lowered into the ocean. [PC: Behnaz Hosseini].
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Once the transponder reaches the seafloor at the targeted site, the float pack is triggered to release toward the surface via an acoustic pulse using an EdgeTech Portable Acoustic Command System (PACS). The time for resurfacing depends on the depth of the site; for our deepest deployments (~4500-5500 m), this time is on the order of 1.5 hours. At the estimated time of resurfacing, the ship's crew in the Bridge searches for the float pack on the surface and navigates to it.
The deckhands use a grappling hook to catch the float pack and guide it toward the stern where it can be hooked and raised onto the deck using the A-frame, a procedure that requires at least 8 personnel. And so everything comes full circle, back to the A-frame.
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| Electronics Technician Dave Price throwing an anchor off the starboard side of the ship to hook a resurfaced float pack. [PC: Behnaz Hosseini]. |
And that, folks, is the [simplified] recipe for a transponder-float pack deployment and retrieval.
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| Watch Group 2 works into the evening, completing their fourth transponder deployment of the day. [PC: Behnaz Hosseini]. |
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