[Cruise Journal 26-29 December]
In this edition: we arrive at the first science dive site, make a small adjustment to Sentry’s planned survey track, and watch Sentry successfully complete Dive 292 of its career.
After quite some time at “cruising” speed of around 11 knots, we finally arrived at the location of our first science dive, number 292 for the Sentry vehicle. While surveying the intended track with shipboard sensors prior to launching Sentry, we noticed a conspicuous sea mount directly along the planned course of the AUV. Since the most consistent magnetic data can be obtained by closely following a level tract of ocean floor, and to make the vehicle’s navigation task as simple as possible, Sentry and science teams decided to adjust the course to bypass the sea mount.
The evening watch and anyone else who was still awake watched the Sentry team and Sikuliaq crew crane the vehicle into the water, and it descended out of view everyone returned to their duties. As the night wore on, everyone on board was pleased to follow Sentry’s progress as the first data collection dive exceeded expectations. As the dive progressed, the Sentry team noticed that the vehicle’s battery was lasting longer than expected, and were able to extend the range of the survey track by increasing the vehicle’s speed slightly.
Given how smoothly this dive went, the Sentry team are looking forward to gradually raising the survey speed of the vehicle in subsequent dives to further extend the amount of seafloor we can survey within each 48-hour turnaround-launch-descent-survey-ascent-retrieval cycle. This is great news for the science mission of the cruise, as longer tracks provide glimpses of more of the magnetic record of the JQZ.
Now, while the AUV’s batteries recharge, we’re towing the DeepTow magnetometer sled to the next dive site, and the Sentry team are preparing to turn the vehicle around for its dive 293.