2450 meters

(2016-01-29) Today the crew on R/V Rahiti Tane sent the Sperre Deepbot camera and the CTD to 2450 meters below the raft. Winds were unsuitable for sailing, and the sail was therefore lowered. 

The instruments, the kevlar line and its bobbin, the electrical winch and the crew got themselves ready immediately afterwards. The operation began at 0100hrs in the universal time UTC, or one hour before sunset. It took 5 hours to spool, first out and then in, almost 4000m of kevlar line. The downcast, technically easier and less energy demanding, took 1.5hrs and the effort of 3 people. Retrieving the instrument demanded full concentration of everybody onboard. They dealt with knots in the line, stuck pulleys, tangled lose line and the tension of a load that included the 10kg bot, 3kg CTD and 10kg rocks as weights. Effective communication, periodical task rotation and properly working instruments and installation resulted in a succesful operation.

The temperature in abyssal depths drops to 2 degrees in the Celcius scale. Three and a half hours of footage were recorded during the cast by the spherical glass-housed Deepbot.

Equipped with two intense led strobes, the deepbot brought to the surface visual evidence of plankton, marine snow and possibly macrofauna, which can be situated with its depth and water physical properties: oxygen, fluorescence, and salinity. A shiny sea surface around the raft, illuminated by the strobes in the middle of an overcast dark night, was a rewarding landscape for the crew indicating the near conclusion of the operation. Both instruments are ready for the next dive. The following morning allowed the overexcercised crew to rest through a pleasant morning, and a harmonius sunrise with a delightfully calm sea.

The picture is a courtesy by our photographer Orlov. The crew gathers around the instruments to celebrate an exciting and demanding activity on board.

[Håkon adds, from a dry place on land: congratulations to Pedro and the Rahiti crew! You have achieved something truly remarkable in the history of oceanography. You beat our previous record of 2046 metres, and you did so with a huge payload, in the dark! The knots on the rope are unfortunate artefacts stemming from the kevlar spaghetti, but I'm happy that the triple fishermen we tied are holding up. Remember, there's a video projector on Tupaq Yapanqi which can project the deep-water footage on the mainsail!]

By Pedro De La Torre