Having gotten the AUV to dive successfully at the test site yesterday, we were excited to return to the site of the wreck of the HMS Stubborn submarine today. We again got on the research vessel "U Boat Navigator" to spend a day out above the wreck.

The U Boat Navigator was again our workspace for the day.

Mounting the sonar on the AUV to prepare for missions.

Before running a mission to collect data on the wreck, we first tested deeper dives of depths around 8 meters. Unfortunately, we quickly saw that the AUV had trouble staying under the water and completing its dives at the depths we wanted. Throughout most of the morning and afternoon, we tried to figure out why this was.

Chris swimming after the diving robot to observe its behavior.

Meanwhile, Zoe and Ian worked on processing multibeam sonar data gathered by the research vessel.

After a long day of searching for the cause of the diving problems, we finally found it. The altimeter on the AUV often received incorrect, very low measurements. This would confuse the AUV into thinking it was about the crash into the seafloor and immediately abort the dive to avoid the crash. We turned off this crash avoidance setting and redeployed the AUV, and it finally dove as desired!

It was late in the day and we didn't have too much power left in the batteries but we were able to send the AUV on a couple lawnmower pattern missions above the wreck at a depth of 20-30m. We still have to process the sonar data from these missions but initial previews suggest we did get an (admittedly noisy) image of the submarine!

Enjoying the top deck of the boat while waiting for the AUV to complete its autonomous data collection.

A plot of the AUV's trajectory, going from blue toward red.