Battery Recharge

Our battery continues to have a much tighter difference between its max and min cell voltages than we did before we replaced supercell #10.

This is what a healthy battery looks like.

The Search for Didemnum: Day 3 (Survey Patterns and Pictures)

Today we worked on our survey pattern behavior. We seem to have some troubles when heading due south.


Aside from that, the surveys look pretty good.


The images we are getting at 2m altitude are a little too pale. You can make out a scallop in this image, but not a lot of red channel is coming through.

We will have to fly lower to get good quality.


At 1.4 meters altitude, things are considerably better!


A crab.


A sea star.


A lobster.


A sunflower sea star, a sculpin, and a "regular" sea star.


We prepared to make the day's first recovery. Working as a team makes what would be an awkward (and somewhat hazardous) process go quite smoothly.


John (the first mate) is very good at coordinating the recovery process.


As the seas get rougher (from 25 kt gusts), deployment gets more "interesting". We try extra-hard to get the vehicle far from the boat before we let it go.


After putting Odyssey back in the water, we weren't able to accomplish much. There were some transient control issues in our way.

We did get a good sense of our minimum turning radius (at cruising speed) when we tried to hold a position.


All in all, we confirmed that the camera system is working reliably that our survey patterns actually look like survey patterns (even if dead reckoning is still a little behind).


Every trip to the surface has pictures filled with these jellyfish.

Ready to Re-deploy

With the RTU overhaul complete, we are ready to get back to hunting Didemnum.

RTU Stress Testing (again)

We did some more stress tests on the RTU after re-tightening the bolts.

Another RTU Overhaul

Back at the lab, the RTU had to be removed so that we could service it.


After draining the oil and opening the housing, it was clear that some of the bolts holding the stator had worked themselves loose again. This is a known issue, caused by a shortcoming in the design of the RTU.

For now, the only thing we can do is re-tighten the bolts and re-assemble the unit.

The Search for Didemnum: Day 2 (Double Success, Double Failure)

On our second day out, we went a few miles further offshore to try some surveys in roughly 100 feet of water. From this far out, we could see the Boston skyline relatively clearly.


The day's first deployment went smoothly.

The goals for our second day out were to find out what altitude is best for taking pictures, and to see if Justin's changes to the survey behavior could help straighten out the tracklines when the vehicle is at depth.


In this test, we stepped through altitudes from 1.8 meters to 1.1 meters in increments of 10 centimeters. The results are exactly what we had hoped for: consistently good images, and a better idea of what range of altitudes will produce them.

Notice the difference in the amount of red channel as the vehicle approaches the bottom. To get good information from red light, we have to fly very close to the bottom. A difference of a few tens of centimeters makes a big difference in light quality!

We also had one flash misfire, the cause of which is unknown.

Overall, this set of images is a huge success; we can start doing image surveys in earnest now that we know the physical focus and aperture settings are in the right place.


The new survey behavior also worked well... mostly. The tracklines are much straighter, but what happened at the 4th corner?

Before we could wonder too much, Justin noticed that the vehicle was running in circles under remote control and had a problem with rolling over.

Uh oh.


Mike and Seth sprang into action to check it out.


Both thruster cables were still attached. So, we decided that recovering Odyssey would be the only way to fully determine the cause of the problem. Kyle got to try his hand at recovery.


Once the vehicle was on deck, the problem was fairly evident. We had lost one of the ninja pins that holds the thruster in proper orientation on the RTU shaft, and the thruster had worked its way to the opposite direction.

Only 3/4" of the thruster was still within the coupling. Had it worked its way fully loose, we would have lost it permanently!

Unfortunately, there was a second problem as well: the RTU had fallen out of alignment, and was unable to produce adequate torque on the shaft to properly position the thrusters. This is a game ender; we have to take the RTU back to the lab for disassembly.


Catching a dogfish lifted our spirits somewhat. We threw it back.


On the steam back to the harbor, I was able to put together a small mosaic of a few good images using the hugin panorama stitcher (not to be confused with the Hugin AUV).

When the RTU is fixed, we should be in very good shape to get more like this!

The Proof: We Actually Did Fix The Battery

It looks like despite the battery problems we had last week, our battery is healthy and doesn't have the one divergent supercell that we noticed during UNH testing.

You can also see the point at which we returned from dinner to find that the power supply had switched off.