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.

The Search for Didemnum: Day 1

Today we started our hunt for the invasive species Didemnum Vexillum. Our equipment was packed and ready to go


We left at 7am to beat the traffic on our way to Scituate.


Once we arrived, we spent the next 2 hours moving our stuff onto the F/V Isabella & Ava and getting it stowed properly.


The boat's crane was big enough (and the tide was high enough) to lift Odyssey IV out of the pickup truck and place it safely on deck.


REx II came too.


Mike, Seth, and Andrew re-assembled the vehicle: fins, thrusters, and thruster guards.


I pieced together the quick-release and recovery pole with appropriate hardware to attach to the boat's crane.


And away we go!


We didn't take any chances on our first deployment; we used the zodiac to pull the AUV away from the side of the boat. Better to err on the side of caution! Our first set of missions was now under way.


The first few dive missions were very disappointing -- the camera only able to capture overly dark images. It was clear that we would have to recover and adjust the aperature.


Rather than recover immediately, Justin took the opportunity to do some survey missions to test the vehicle's "survey behavior" functionality.


The first survey (done on the surface) was a poor performer. The vehicle didn't really stay on each of its tracklines before reaching the next of its waypoints.


Making the tracklines longer (again on the surface) produced a much cleaner lawnmower survey pattern.


Running the survey at depth showed us that we still have a few control bugs to work out. With that, it was time to recover the vehicle and adjust the camera.


Instead of taking the entire vehicle apart, we were able to simply remove the bottom fairing and open up the bottom end of the camera bottle with a strap wrench that they had on the boat. We were able to re-adjust the camera in record time!

Not shown: the recovery process. I got to try out my new recovery pole, and it worked like a charm! I snagged the vehicle on the first try.


With the camera adjustment done, it was time to re-deploy. We were much more confident the second time around.

If you look closely, you can see the horizon tilt as the boat heels over due to the weight of the AUV. This helped keep spacing between the AUV and the gunwale.


Our quick-release hook makes life very easy.


The next camera test was also disappointing.

"I think my eyes are getting better. Instead of a big dark blur, I see a big light blur."

These pictures were taken at a 2-meter altitude, and you can see hints of the sea floor if you squint.


We decided to go even lower -- to 1 meter -- which puts us at the limit of what our DVL is able to sense for altitude.

But we finally captured some good images of the sea floor with our new camera system! This is excellent!

The only problem is that the best image in this set (frame 236) was taken without a DVL lock, so we have no idea what altitude produced it. The images before and after it are no help either.


Since we had to get back to the harbor before low tide, it was time for the second recovery of the day.

If you look closely at the top row, you'll see the new recovery pole in action. The boat captain was an excellent crane operator and the vehicle was back in its cradle in just a few moments.


We steamed back to Scituate.


This was our one good result of the day. It's not much, but it proves that the camera's physical settings don't need to be changed; all we need to do is tweak parameters tomorrow to get more images like this one.


We set up the charger before dinner, but after eating we checked on it and noticed that the power supply had tripped. This was probably when the boat's power was switched over to the auxiliary generator.


Back to the hotel! One day of testing down, 4 to go!

New Recovery Pole

I put together a recovery pole for Odyssey IV out of some spare steel tubing, some hose clamps, a carabiner, and a length of 3/4" EMT conduit.


The carabiner will be attached to the ship's crane, and will slip out of the pole once it has been clipped to the vehicle's lifting bail. We will find out how well it works next week!