Monday, July 21, 2008

Gavia Blog

On July 12, 2008 we arrived at CCOM at UNH to begin testing the lab's
newest technology, the AUV Gavia, which was arriving from Iceland! When we
first entered the workshop Eggert, an engineer working on the Gavia, was
connecting the batteries (Photo 3338). Since I've never worked with
anything like this, Eggert told me some amazing details about how the
Gavia can operate for 2-4 hours in 5-40 m of water with an impressive
array of instruments (sidescan sonar, Geoswath, ADCP, camera, propulsion
and navigation system, oxygen sensor, and flourometer…) running. The Gavia
is controlled by four computer, which must be carefully sealed in the
aluminum casing so they remain dry. I was very excited to see the Gavia
and couldn't wait to test it in the tanks on Monday!

July 13, 2008
We got up early anticipating the need for a lot of tinkering with the
Gavia to make it work. Labmates Hilary and Stephanie have cautioned me
with tales of past AUV operations; however, all signs were good when we
started the Gavia: it turned on, the props worked, and all systems were
operational. Everyone cheered when we put the Gavia in the tanks for the
first time and all the lights turned on (Photo 3369). The one
disappointment is that the Gavia's accident avoidance system was so
sensitive that Gavia could not safely maneuver in the tank. Instead we
were able to run an endurance "stress" test to see how long the Gavia
could run with all systems operating. We got about 3.5 hours of operation,
with the AUV operating at different speeds. Throughout the test the Gavia
was tethered to the pool and slurped and burped the water unhappily,
wanting to swim free.

July 14, 2008
Morning camera calibration tests went so smoothly that we were able to
take the Gavia on its first experience in U.S. waters at Adam's Point
(Photo 3395). We trimmed the Gavia, slowly moving weights from bow to
stern and making incremental changes in weight, so the Gavia would float
evenly in the water. Test dives from the dock showed that once again, the
accident avoidance system is very sensitive, making causing the Gavia to
abort dives and missions. On the last dive the Gavia moved out of Wi-Fi
range and was rapidly being swept away by a strong tidal current. Luckily
a UNH student let us hop on his boat and rescue the Gavia before it

July 15, 2008
Today was a big day at CCOM, as it was the annual review by NOAA, and we
got to show off our AUV. We also worked with George Tait from Geometrics,
who is helping determine if we can add a magnetometer to the Gavia. We
tested this in the tanks by measuring changes in the magnetic field while
the Gavia operated with different instruments and at different speeds. In
photo 3405 labmate, Stephanie, keeps a hold on the Gavia while
demonstrating how it flies through the water. Preliminary results suggest
it will work! Eggert tutored us in the afternoon about how to operate the
Gavia using the computer controls, which at first seemed very complex, but
after he explained the system, seemed pretty user-friendly.

July 16, 2008
We got an early start on the day so we could spend as much time in the
field as possible. Eggert tinkered with the accident avoidance system to
take into account the vehicle length, which is longer than the ones they
are used to working with, and pitch, so we had high hope of getting some
good data. The Gavia was still having problems with oversensitivity of
the accident avoidance system, so Eggert turned that system off. We held
our breaths waiting for the vehicle to resurface after the first mission
in Great Bay (Photo 3414). Although we had to search for the Gavia it was
able to complete 4 transects. It was having some trouble with eel grass
fouling the props and moving against strong tidal currents. In the
afternoon we sent the Gavia out in Little Bay, where 2 transects were
completed before the props were too fouled to move against the currents.
In the late afternoon we reviewed our data and found that most systems
were operating well, although there is some problem with the DVL rejecting
the GPS data. Overall, the Gavia looks like a great tool for mapping the
seafloor and taking basic measurements once some problems can be resolved,
especially with the accident avoidance system, Wi-Fi connection and
communication with the computer to aid in navigation and locating the
vehicle post-mission.

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