November 22: Hydrophone recovery
Recovering the hydrophones
November 22, 2006
On board the RV Yuzhmorgeologiya
Drake Passage off of Antarctica
We awoke early this morning in anticipation of recovering the first of seven hydrophones deployed last year. The RV Yuzhmorgeologiya had already arrived to its station at 60 degrees, 30.00 minutes South, 61 degrees, 00.00 degrees West. The seas were smooth with long swells. Unfortunately, fog settled in and visibility was severely limited. Using the GPS we knew we were in the right area, but because of ship noise, the hydrophone couldn’t be immediately located.
Haru listens for the tell-tale chirp
With a portable deck box and transducer, Haru tried different locations until the sonic chirp of the hydrophone was detected. But because of the fog, the acoustical release wasn’t immediately signaled. Once released from the weight of the railroad wheel, the hydrophone would rise to the surface pulled by the buoyancy of its yellow, syntactic foam float. Even with a flashing strobe light, the float would be difficult to locate in heavy fog. The decision was made to wait until fog dissipated to signal the acoustic release.
Recovering a float
The fog eventually lifted shortly before noon. Most of the crew gathered on the foredeck, scanning the horizon for the telltale float. The yellow float broke the surface less than 50 meters from the Yuzhmorgeologiya. With a grappling hook, a member of the crew secured a line to the float and moved it to the stern of the ship. Using the “A” frame there, the float assembly was raised to the deck, securing its important cargo. The hydrophone was quickly transported below decks where Haru determined that last year’s acoustic data was secure.
Inspecting the recovered hydrophone