The Search for Didemnum: Day 5 (Now THAT'S More Like It)

We got off to a great start!

Clear water, proper bottom type, and great lighting. Today is a day to find didemnum!


With the vehicle fully functional after the previous day's repairs, Seth and Mike began fishing in earnest.


We're no experts on identifying tunicates, but we had no problem finding spectacular examples of sea life amongst the volumes of images that Odyssey brought back.

This is a sunflower sea star.


A skate...


A flounder, doing a good job of blending in...


A tiny solaster (literally, a sun star)...


After taking a few thousand pictures, we decided to seek out more rocky bottomed waters by moving further east.

Our recovery was complicated by the rocking of the boat, but as a team we are getting used to handling the swinging vehicle.


(There were also some good pictures of the water column!)


Our second deployment went very smoothly.


Unfortunately, the water was far more turbid in our second area of operation. Sponges, anemones, and redfish dominated the images.


The sponges look like potatoes in these images.


Although beautiful to look at, anemones are not what we are after.


As the light faded, we made our last recovery for the week and prepared to head back.


We had pictures of too many starfish to count, in all shapes and sizes.


This one was hanging out inside a mussel shell. I can't tell if it's eating or just resting.


There were also quite a few crabs, hermit crabs, and sunflower sea stars.

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.