Tuesday, August 7, 2012

AUV Adventures as told by Intern, Continued

After several days of testing each AUV module and ballasting the vehicle, we were ready to run missions offshore and observe their execution. Again, the purpose of this trip up to the Center for Coastal and Ocean Mapping (CCOM) at the University of New Hampshire was to prepare the vehicle for AUV Boot Camp in a few weeks. Therefore, it was important to run missions in the water in addition to the bench tests we performed onshore.


Tuesday brought two things- our first day at sea, and Art. Art flew in to Manchester late the previous evening, and Justin and I collected him from the airport early Tuesday morning. We headed straight to the UNH pier to meet with Val and Jen, a marine ecologist who joined us for our offshore missions. The five of us boarded the R/V Cocheco, a 34-foot CCOM vessel captained by Emily Terry. I learned a little bit about creating mission lines for the AUV. By typing a latitude and longitude for the start and end point, you create a line that the AUV will follow when the mission is executed. From there, you can adjust which devices and features are active during that line. For example, we could enable the camera to take one picture every second during that line, and then choose to disable it for the next line. We can also choose between a constant depth or altitude off the seafloor, constant speed or rpm, and a variety of other factors. Once the mission is modified in the desired way, we can upload the mission to the AUV, and then execute it.


All of our missions were successful on Tuesday, and it was really neat for me to see the AUV in action for the first time. Our high frequency sonar images came out wonderfully, with the bedforms clearly visible and defined. We even virtually captured a lobster from one of our camera images (spot it in the image below). Despite our success, it was slightly nerve-racking every time we broke our physical connections to the AUV and tossed it into the sea. Although we did have several forms of communication between us and the vehicle, there is definitely some anxiety when dealing with such a valuable piece of equipment. One of these means of communication is our iridium phone. When the AUV surfaces, the phone receives a text message saying that mission has completed (or failed) along with the coordinates of the surfaced vehicle.


After the completion of the day's final mission, strong currents drove the AUV through an area of lobster buoys, resulting in a bit of a chase before we were able to recover the AUV onboard. Art phrased the situation "an expensive game of Marco Polo." Marco Polo it may be, but we'll always consider it a success when we have the same number of recoveries as we do deployments.


We set out the next day for our second and final excursion at sea. Our objective was to map areas near the Isles of Shoals containing certain macroalgae for Jen. She is currently investigating various methods of image analysis for these macroalgae, and could potentially use the AUV for future research. I was surprised that the algae were large and solid enough to be visible via sonar. We also mounted a GoPro camera on the bottom of the vehicle for another form of image collection. Our first two lines were completed without error, but due to a time constraint, we altered our initial plan to combine  our last missions into one. The AUV was deployed as usual, but after about ten minutes, the iridium phone received a text message reading that the mission had aborted. Now what? The AUV was out there somewhere, floating at the surface after unsuccessfully attempting to complete the mission we programmed for it. Everyone kept their eyes locked on the waves, waiting anxiously for a flash of gold. Luckily, we were able to recover the AUV rather quickly. Unfortunately, the plastic tip of the nose cone looked as if it had collided rather hard into the seafloor. It is likely that the bathymetry of the seafloor changed too quickly for the vehicle to maintain its altitude from the bottom without colliding with anything. From the aborted mission, I learned that careful planning is one of the most important parts of using an AUV. When we ran out of time, we decided to make changes on the fly, which can lead to unintended errors.


In the ten days that I was in New Hampshire, I learned a lot. I got a crash course in everything AUV, and I feel more adequately prepared for boot camp in less than two weeks. It is really amazing to me how much of the AUV's capabilities I saw, knowing that this is just scraping the surface of what this vehicle can do. I am looking forward to boot camp, where I will be in the midst of even more talented people and surely learn exponentially more about our AUV.


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