2016.07.03 – On our way to the Azores

Lawrence (right) and Ian (left) prepare DASI for launch

We are now in the Western European Basin and have taken the opportunity to stop for 24 hours to test our Deep Active Source Instrument (DASI) and Vulcan electromagnetic survey system. This is the first time we have deployed such a complex array. At the front we have the DASI electromagnetic source, which is a powerful electrical signal generator. It tows an array consisting of a 75m antennae of thick copper cables, followed by a 300m line towing a receiver, Vulcan One, another 150m line towing Vulcan Two, and a 10m line towing an acoustic navigation beacon. DASI has an acoustic navigation beacon and we are testing the towing geometry as we descend to 3500m.

DASI transmitter (far distance) the USBL tail and Vulcan One lined up ready for launch on the aft deck of the RRS James Cook

The acoustic navigation allows us to see the position and depth of the DASI and its towed array as we maneuver through a course of different depths and turns. Although we are only moving at 1 knot (about 0.5m/second) the array responds quickly to our changes in the winch and length of tow cable. We are trying to thread the DASI and array through points that are at different depths and at different positions. The array has floats to keep it neutrally buoyant. It must not float too far above or below the DASI in case we hit the seafloor! Ross, our Sonadyne Ltd. engineer, has been working hard to make sure all the underwater navigation systems operate well, which they have been, most of the time!

Romina keeps the electrodes on Vulcan One wetted with seawater, covering with wet cloth to prevent them drying out.

DASI is the last to go into the water, towing the 500m array behind her

Life onboard is setting into a routine of work (12 hours a day) and rest. Everyone looks forward to mealtimes. On Saturday it was curry time, and on Sunday it was steak night. The chef, John, the cook, Steve and the steward, Peter, work hard all day to provide us with a variety of tasty dishes. There is a saying at sea that goes “a well fed crew is a happy crew”. I would add that on a British ship, a constant supply of cups of tea is also an essential ingredient.

The weather remains grey and overcast, but at last the sea has calmed and everyone is feeling well. We are looking forward to getting further south and into proper summer weather.