The fifteen instruments to be recovered were some of those that were deployed from the October voyage of the Wecoma. These are the Scripps Institute of Oceanography “Abalones”. Abalones are trawl-resistant, three component, battery powered ocean bottom seismometers, capable of being deployed in water depths of 50 to 6000 meters. We are recovering them via an acoustic release. After cruising to the proper latitude and longitude, an acoustic signal is sent down from the ship to “wake up” the Abalone’s acoustic release. The Abalone acknowledges by sending back its own acoustic signal. We then send a signal down to the acoustic release burn wire. The burn wire is an alloy of nickel and chromium. When an electric current is passed through it, the burn wire begins to oxidize. After about seven and a half minutes, the Abalone separates from its steel ballast and floats to the surface at about 60 meters per minute.
The first Abalone slated for recovery (Y1M7) was deployed in 1356 meters of water. After its 22-minute ascent, the strobe from the first Abalone was sighted at 22:05. The rough seas and high wind complicated recovery. The deck crew missed the first pass, and the New Horizon had a difficult time keeping the floating Abalone along its starboard side. Eventually we secured our first recovery to the deck at 22:45.
We will cruse through the night to our second station (Y1M5).