The tether management system sits on top of the ROV during deployment and recovery of the sub, and is suspended by the support vessel above the ocean floor during dives. It manages the tether line for the ROV as it moves down to the ocean floor, ensuring that it doesnt drag along the bottom, and is secondarily used for sample storage, as can be seen from the various baskets hanging from the frame.
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Gulf of Mexico Deep Sea Habitats 2003