Education: Technology and Collaboration
|Explain how new technology can enhance the gathering and manipulation of oceanic data (NSES,176; NAAEE,51,52; OLS,14)|
|Explain that ocean science is interdisciplinary and requires new ways of thinking (NSES,192; OLS,14)|
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Leveraging a Sensor Web Dr.Eric Lindstrom explains
How Can Technology and Collaboration Enhance Understanding of the Ocean?NASA's Aquarius instrument, launched onboard a Delta II rocket from Vandenberg Air Force Base in California on June 10, 2011, provided global-scale data critical to our understanding of the water cycle, ocean circulation, and climate until June 8, 2015. The satellite flew 657 kilometers (408 miles) above Earth in an orbit that repeated every seven days. Aquarius data are used to make monthly maps of sea surface salinity which allow scientists to resolve global salinity changes from month-to-month, season-to-season, and year-to-year. The Aquarius/SAC-D mission is a collaboration between NASA and Argentina's space agency, Comisión Nacional de Actividades Espaciales.
Featured Movie: Aquarius and the Water Cycle
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Articles & Documents
- Aquarius Launch Details
- Aquarius/SAC-D: Sea Surface Salinity from Space
- The Aquarius/SAC-D Mission: Designed to Meet the Salinity Remote-Sensing Challenge
- What's Next for Salinity?
- How is the Aquarius/SAC-D Mission important to everyday citizens of Argentina?
Everybody in Argentina has been following the launch of this satellite through public television and other media. The (Argentine) President was present during the transmission (of the launch). Children in schools will be receiving the information from the satellite so it's something that is not only a success or victory or something important for the scientists but it's important for the whole country. It's important to feel how proud we are of something that is sometimes very difficult to understand but that we know that somewhere in our hearts that this is a triumph of a bet that we made many years ago in Argentina. As Dr. Varotto has said, there are dreams that are worth following.Hector Timerman, Foreign Minister of Argentina.
- Why did NASA pick Argentina as its partner on this mission?
There is a history of partnership with Argentina from the earlier (i.e., SAC series) missions. Teaming and partnering with Argentina and other international organizations allows NASA to accomplish more than we can alone, just from the simple economics. Argentina has a proven track record in partnering with NASA and we were pleased and proud to be associated with Argentina for Aquarius/SAC-D. -Charles Gay
Argentina and our past collaborations with them have really helped to advance our understanding of the earth. Understanding the earth as an integrated, complex system is way too hard for any single nation, any single agency. We need to have partners who are willing to truly collaborate: not simply take orders or give orders, who have vision, who have sustained effort and are willing to attack the challenges that arise during the many years that these missions are under development. Argentina has proven time and time again, with NASA and in other ways, that the spirit of that nation - as well as the competence of (its) scientists - is there. And NASA is indeed proud to be a collaborator with Argentina and the other international collaborators on this mission. -Michael FreilichCharles Gay, Deputy Associate Administrator, NASA Science Mission Directorate and Michael Freilich, NASA Earth Science Division Director.
- What is the nature of NASA's partnership with Argentina?
SAC-A, launched by Endeavour in 1998, characterized the performance of equipment and technologies for future missions. SAC-B was designed to study solar physics and astrophysics using science instruments from CONAE, NASA, and the Italian Space Agency (Agenzia Spaziale Italiana, ASI). Launched in November 2000, SAC-C focuses on Earth observations such as monitoring Argentina's soil conditions and marine ecosystems.
Aquarius/SAC-D is the fourth satellite in this partnership. Overall mission design has been developed collaboratively between NASA and CONAE to best meet the goals of each agency while giving priority to salinity measurements. CONAE built complementary sensors to detect rain, sea ice, and wind speed, plus sea surface temperature sampling. CONAE- sponsored instruments - including sensors from the French Space Agency (Centre National d'Etudes Spatiales, CNES) and another from ASI - provide environmental data for a wide range of applications, including natural hazards, land processes, epidemiological studies, and air quality issues.
- Who is using the data collected by the Aquarius satellite and for what purpose?
In fact, if you look back over all the measurements that have been made from ships over the last 50 years and you map the changes in salinity you actually find that most of the saltier places in the ocean surface have gotten saltier and the fresher places have gotten fresher, which is exactly the fingerprint that you would think to see in an acceleration of the water cycle. So as Aquarius is coming along ocean scientists are trying to diagnose if this is really true, that there is an acceleration. We have to act like a doctor doing diagnostics on a human, we have to rule out other diseases so what we're trying to do with salinity here is rule out that it's not ocean processes fooling us to make it look like an acceleration of the water cycle. Want to read more from Eric's interview? Click here.Eric Lindstrom, Program Scientist in the Science Mission Directorate at NASA Headquarters in Oceans and Climate Change, Pod Academy, March 22, 2012.
- Do you have plans to share data between the two groups (SMOS and Aquarius)?
Absolutely. The two groups have been working in concert from the very beginning of the development of both missions. We participated in each other's science team meetings. I sat on the SMOS Science Advisory Group for about seven or eight years and we've been sharing information, algorithms, approaches to problems, things like that. There's been a great deal of communication between the two groups and we sort of see each other as one team supporting two missions in a lot of ways.Gary Lagerloef, Aquarius Principal Investigator.
- What was the reason the (Aquarius) satellite was initially built?
So more than 3/4 of the global water cycle is just the exchange of water between the ocean and the atmosphere. Now that said, we don't really know much about how that affects the ocean. We know it governs the broad-scale patterns of ocean salinity but how small changes in rainfall and evaporation affect the sea surface and how it affects ocean circulation are still largely unknown. That's the essence of what we want to investigate with Aquarius by mapping those variations in sea surface salinity, relating them to rainfall data that we collect from satellites, relating them to ocean temperature data that we collect from satellites, and relating it to ocean circulation data that we collect from satellites. So, in a way, Aquarius is filling in a "missing piece" of information that we really need to completely understand the role of the ocean in regulating climate and interacting with the atmosphere. That's the reason why we built Aquarius. -Gary Lagerloef
I would just like to add that it's what we call a "Pathfinder Mission" so it has the objectives of demonstrating the technology to measure salinity and then applying the salinity measurements to understanding of ocean dynamics, weather and climate, and the water cycle. -David Le VineGary Lagerloef, Aquarius Principal Investigator and David Le Vine, Deputy Principal Investigator in How Do We Cover the Globe with Aquarius Data? NASA's Aquarius Studies Our Salty Seas Webinar, January 17, 2012 (Session 2).
- Can you explain "brightness temperature"?
Another example of natural radiation is the heating of your electric stove. You turn on the burner, it warms up, and it glows red because it has gotten more energy and the added energy changes its frequency distribution. Now because it's so hot, it actually gives off more energy in the optical frequencies that our eyes are sensitive to. But it is also putting off radiation at all frequencies. So if we looked at it with night vision, then it would be overwhelmingly bright. And if you looked at it in the microwave frequency range (e.g., 1.41 GigaHertz, GHz like the Aquarius instrument measures), it would also look very bright. So it's giving off energy.
We talk about that energy as an equivalent temperature. So you can say that if the temperature is higher, there is more energy and if the temperature is lower, then there is less energy. The scale isn't so important because it depends on the frequency (e.g., the same temperature scale wouldn't work for the night vision scale at the infrared frequencies). But we have a scale called "Brightness Temperature" that is measuring the amount of energy that's being given off by the ocean surface at a fixed temperature.
So in the graph above right (click image to enlarge), go along the horizontal axis and stop at a sea surface temperature (SST) equal to 20 degrees Celsius (see blue box). If you go up to the blue line labeled "12 psu" (practical salinity units, psu), you'll see a purple arrow. If you read across to the vertical axis (i.e., follow the purple dashed line to the left), you see that lower salinity water gives off higher energy because the Brightness Temperature is about 104. At that same SST of 20 degrees Celsius, higher salinity water (see red arrow at 42 psu), gives of relatively lower energy (i.e., follow the red dashed line to Brightness Temperature on the vertical axis at about 88).
Aquarius has a very precise instrument that tells us how much energy is coming off the ocean surface and we express that as a "Brightness temperature". If the brightness temperature is higher, then the seawater is fresher (i.e., less salty; see pruple arrow / dashed line above). If the brightness temperature is lower, then the seawater has more salt (i.e., red arrow / dashed line). The graph shown at right was published in 1977. So an important new area of research is to develop a set of curves that are very carefully calibrated so we know exactly what energy corresponds to what salinity. And the instrument we use is very precise and makes these measurements accurately and consistently.David Le Vine, Deputy Principal Investigator in How Do We Cover the Globe with Aquarius Data? NASA's Aquarius Studies Our Salty Seas Webinar, January 17, 2012 (Session 2).
- The European SMOS mission has been trying to measure ocean salinity over a year. The mission has had issues as a result of radio frequency interference (RFI), not just soil moisture but over the oceans as well and no doubt you're going to encounter that experience too. Your thoughts on Aquarius and RFI?
So, the other factor is that SMOS employs a thinned aperture, phased ray design which is much more difficult to calibrate than Aquarius is going to be and so they're running into some of those problems. With regard to the radio frequency interference issue that you mentioned - that has plagued SMOS. They've done a lot of work on dealing with some of the emitters, particularly in northern Europe. Aquarius actually anticipated this problem and one of the other technological factors that went into the design of the Aquarius instrument was that we have actually tested and built an RFI filter using measurements that we've taken from rooftops and other places to see what the characteristics of that radio interference would be. So we built a filter into the processor - it hasn't been tested from space yet - but we think we'll have sort of a leg up on that problem once we get on orbit.Gary Lagerloef, Aquarius Principal Investigator.