Tale of the Tape
RU17 was deployed on May 21, 2008 and was within 20 km of the Azores EEZ line when we lost communications on October 28, 2008. The Rutgers students, technical staff and scientists flew RU17 a record breaking distance of 5,700.59 km. We spent 160 days at sea, which translates to 22 weeks and 6 days, or 5 months and 1 week depending on your preferred measure of time. There is no Guinness Book for glider statistics, so we have to rely on the public websites we can find. Based on that search, it looks like we share the duration/distance records with our friends at the University of Washington. Glider RU17 now holds the world record for the longest distance mission for an autonomous underwater glider – 5,700 km. A University of Washington Seaglider holds the world record for the longest duration mission – 7 months.
The primary purpose of this flight was education. We where challenged by NOAA to fly a glider across the Atlantic on an inspirational flight that entrained students. Funding for this purpose was provided through donations from Rutgers Alumni. The private funds were used to build RU17, which was christened The Scarlet Knight by the Rutgers President in honor of the Rutgers-wide involvement that not only crossed campuses, schools and departments, but also crossed generations of students in the Rutgers family.
Over the course of building RU17, the test Flight to Halifax, and the Across the Pond experience, undergraduate involvement in the Coastal Ocean Observation Lab has increased by an order of magnitude. We typically had 1 or 2 undergraduates in the Lab on a regular basis, including a record setting 3 undergraduates in 1994. Now, depending on how you count, we have been 10 and 20 undergraduates working in the Lab.
We see the undergraduate students are seeking new opportunities earlier in their careers. In the past the majority of students came to us during their Junior year. Occasionally we would entrain the rare Sophomore, a lucky break because we would both benefit from the opportunity to spend two summers together. Now, attracted by the grand scale of international glider missions, we are even pulling in Freshmen through the various Intro to Oceanography courses and Freshman seminars that we use as feeders. Workstudy students are seeking us out during the school year. Traditional summer internships are being used to attract students from outside Rutgers, and to send Rutgers students abroad. Some Seniors are staying with us through the summer after graduation before they move on. Some of the new Freshman will have spent 4 years working with us in the Lab over the course of their undergraduate careers. The students are seeking both the hands-on research opportunities and the camaraderie of a group project that RU17 provided. They are prompting us to teach more mid-level undergraduate courses. Our traditional capstone courses, for example, the first year graduate course in Physical Oceanography, are still being taken, but the capstone course I now recommend for their final semester is Communicating Ocean Science, an NSF sponsored class developed by Lawrence Hall of Science. The course introduces them to modern educational theory, it provides hand-on opportunities to practice what they learn at Liberty Science Center, and they use that experience as a basis for mentoring the younger multi-disciplinary students in the lab. Even after graduation, we see that the students use the new tools available to them, like video IM and Skype to stay in touch, and to field questions from younger students that are just starting out.
What did the students do during this project? We had several small teams or sometimes individuals contributing to a common goal. Two students helped with the glider build itself. Two worked on determining and improving the flight characteristics of RU17, including work on the flight characteristics of the extended payload bay, energy savings on communications and trim battery movements, and optimizing the gains on the Digifin for improved steering. Two worked on the CODAR network in the U.S. as the take off point, one went to Spain to work on their CODAR network as a potential landing point. One worked on path planning and the new Google Earth and Google Maps interfaces. Another worked on the webpage interface describing what we are doing. During the summer, the more senior level students took full control of the flight planning and waypoint changes. During the fall semester, the younger students came in and filled their shoes.
The most interesting scientific discovery of this mission has been the interaction of the glider with the upper ocean biological communities of the central North Atlantic. After leaving the Gulf Stream region and heading east of the Grand Banks of Newfoundland, we noted a decrease in glider speed on both upcasts and downcasts, resulting in fewer undulations per 6 hour segment. The suspected cause is biofouling, since the speed decrease was slow and steady for a period of about a month before it leveled off at a slower but steady speed.
The new discovery for us was the difference in the day-night behavior of the upcasts and downcasts. The upcasts were sensitive to the day night cycle, downcasts were not. There were many times when the upcast speed at night was much slower than the upcast speed during the day. Many times at night we would have trouble making it to the top of an undulation. The glider would be slowed to a stop, and would have to turn around and go back down before trying again to ascend. Yet throughout the mission, downcast speeds showed no day-night variation. Interactions with either remoras and squid were suggested as possible explanations. We have seen Remoras attached to gliders in the past, and we know they are negatively buoyant, which could explain the glider’s reluctance to climb if a remora was attached. Remoras also use their vision to hunt for food, so its been suggested that they may prefer hitching a ride on a glider at night when they have nothing better to do.
The other interesting part was that the occurrence of slow nighttime upcasts appeared to vary in space and time. There was one eddy in particular that we saw the slow upcasts whenever we were in it. Another cycle we noticed followed the new moon. There were two new moons that RU17 started flying in a tight circle as if something had grabbed onto one side or the other. During one full moon it circled to the left, the other it circled to the right. It was suggested that bioluminescence was making the glider very visible during the new moon, and the glowing glider was attracting squid. Assuming something was attached to the glider, we tried a new procedure to fly the glider backwards, pulling water in the nose to make it heavy but shifting the batteries all the way back so that it sank tail first.
The flight of RU17 was conducted in the enduring spirit of the National Ocean Partnership Program. In effect, it launched an unfunded International Ocean Partnership Program that united a community within the U.S. and across the Atlantic. Having a glider deployed at sea motivated collaborations that may otherwise have taken years to develop. Path planning for RU17 required data and forecasts, and operational centers with existing products were eager to contribute to the success of the mission. The University of Maine provided a link to their satellite data when the Rutgers acquisition system went down and required repairs. A similar satellite receiving station in the Canaries provided local coverage on the European side. The NASA Ocean Color Web provided access to the global MODIS dataset for SST and Chlorophyll that filled the gap between the higher resolution direct broadcast data acquired on either side of the Atlantic. The Altimetry products generated by the University of Colorado, especially the geostrophic currents, were in constant use. Ocean model forecasts were provided by the Naval Oceanographic Command and by our partners in Spain. The NOAA National Hurricane Center and Oceanweather websites provided wind and wave forecasts. The international Argo program provided subsurface temperature and salinity profiles for ballasting and flight planning.
All the above datasets were combined in a Google Earth interface that was built by students and hardened by research programmers at Rutgers. The purpose was to overlay datasets and glider positions for mission planning and waypoint selection. Software was developed to go directly from the Google Earth mouse clicks to the glider waypoint files that sit in the glider’s Dockserver mailbox waiting to be sent at the next surfacing. The Google Earth interface proved to be extremely popular with bloggers and pilots. It has already been transferred to other glider operators throughout the U.S. It was especially well received by the NAVO glider pilots at Stennis Space Center. They used the interface to mission plan for gliders deployed in two Navy Exercises, BALTOPS with NATO and RIMPAC in the Pacific. At the recent Integrated Ocean Observing System (IOOS) Mid Atlantic Coastal Ocean Observing Regional Association (MACOORA) annual meeting, the interface was one of three adopted by the data management team for implementation during year 2 of MACOORA’s Mid Atlantic Regional Coastal Ocean Observing System (MARCOOS).
As part of our IOOS Mid-Atlantic Regional Coastal Ocean Observing System (MARCOOS), we started glider flights that ran from state to state in the Mid-Atlantic. Regular gliders flights are now maintained between the U. Massachusetts-Dartmouth and Rutgers, and between Rutgers and U. Maryland / U. North Carolina. At the semi-annual MARCOOS meeting in the fall of 2007, it was determined that an advanced glider training course was required to maintain this network. Rutgers developed the Glider School 102 as a follow-on to the Webb Research Glider 101 course. It was first taught in the intersession before the start of the Spring 2008 semester so that all the undergraduates preparing for the upcoming test Flight to Halifax and the eventual flight across the Atlantic could take the course. They were joined by our IOOS partners, a few glider pilots from NAVO, and some glider operators from Plymouth, England. One of the undergraduates from the U. Maryland that participated in the course later applied for a NSF RIOS summer internship and ended up spending the summer with us flying RU17.
Interest in the Glider Training 102 course also expanded with the Flight to Halifax and the subsequent flight of RU17. The course was given twice more, once in the spring and again in the summer, as training for additional NAVO glider pilots. During the class, the NAVO pilots started using the same Google Earth interface to fly RU01 in the Baltic that we were using to fly RU17 in the Atlantic. With our growing connections in Europe, we were invited by the European Glider Organization (EGO) to join them in a European Glider School conducted in Italy at the NATO facility in the fall.
With the rapid expansion of glider operations in the U.S., Europe and Australia, the community is going to need more people training in the operation, maintenance and use of gliders for ocean research and operations. Last year two seniors graduated from our lab. One went to work in the Caymans on NOAA projects. The other went to Georgia Tech to work with a young faculty advisor starting a new glider lab. On their last visit, NAVO posted job advertisements in the lab. They are developing a significant glider capability, and they will be needing new people. They are especially interested in the students that graduate from our lab, and are willing to pay for their Masters degrees if they head down to NAVO after they finish the undergraduate program at Rutgers.
RU17 served as a test case for three major changes on the Standard Slocum Glider. Any of these changes could be tested with dedicated flights in our Mid-Atlantic testbed. With RU17 we were able to leverage the tests into one long-duration mission.
This was the longest duration test to date of the new Digifin developed as part of the glider hardening work for ONR. The earlier style fins were more susceptible to damage. The Digifin design is more compact and strong enough to be grabbed without breaking. It performed well the entire trip, continuing to call in even during the highest seas, and remained tunable throughout the mission as flight characteristics changed.
The Lithium Batteries were tested for a NOAA NOPP project to install a kinetic Fluorescence, Induction and Relaxation (FIRe) sensor on a glider. For the techno-folks, the FIRe sensor measures the quantum yield of stable charge separation at photo system II. For the rest of us, this provides an extremely sensitive proxy for phytoplankton physiological status. In other words, are the forests of the sea healthy. Light sources used by the FIRe sensor require a lot more power than most sensors, so Lithium batteries are strong option for envisioned long-term deployments of the FIRe.
The extended payload bay was tested for future deployments at the NSF LTER located on the Antarctic Peninsula. The distance between the U.S. station in Palmer and the British station in Rothera is to far for a standard glider on Alkaline Batteries. Lithiums are difficult to ship and don’t like the cold. Using the space inside the extended payload bay for additional Alkaline batteries, it is now theoretically possible to cover the full distance between Palmer and Rothera with a single deployment. The flight of RU17 demonstrates that the extended payload bay is a viable option when longer duration missions are required.
In the process of conducting this mission, engineering observations were continuously shared with Webb Research, the designer and manufacturer of Slocum gliders. This feedback helped Webb identify and prioritize software and hardware upgrades that impact all gliders. Specific examples include positive control of the buoyancy pump when a downward inflection is initiated at depth (this prevents the high water pressure from generating heat by pushing the pump in faster than intended), additional energy savings modes and a range of new gain values for the control of the Digifin, the ability to cross UTM navigation zones without restarting a mission, the design of new wing rails for attaching the wings to extended payload bays, etc, etc. This feedback loop is how we have operated with Webb Research as a NOPP partnership initiated in 1998. Electrochem, the manufacturer of the Lithium Batteries, has now joined this partnership.
Our students serve as ambassadors for Rutgers and for ocean science and technology. They brought gliders to high schools around the state and explained how young students at Rutgers can get involved. They flew the gliders in the pond on campus during the public Agricultural Field Day, attracting news media coverage. The Flight to Halifax attracted coverage in the U.S. and Canada, and the midway point in the flight across the pond produced an Associated Press article that was printed in hundreds of newspapers around the world. Chip and I were at the RIMPAC exercise in Hawaii, walking a glider down the public dock to a deployment vessel. We were surprised that everyone knew what it was, commenting how it looked just like the one that was trying to cross the Atlantic. In another example, we were at the Liberty Science Center, teaching a class in their Delta Lab, a lab set up to look like the Rutgers COOLroom. The middle school students we met that day told us Rutgers was famous for football, basketball and gliders.
This was a risky mission. Everyone knew that. We also knew that we would learn a lot more by trying than by staying at home.
We tried once. We learned a lot. We'll try again in the Spring.