Ohio State Researchers Team Up For NASA Satellite; ICESat To Map Earth's Ice Sheets

The mapping software is one of several contributions that Ohio State is making to NASA's Ice, Cloud, and land Elevation Satellite (ICESat), said Bea Csatho, senior research associate at Ohio State's Byrd Polar Research Center (BPRC).

Csatho heads the university's ICESat team, which is working with Robert Thomas, a scientist for EG&G Services at NASA's Wallops Flight Facility, Wallops Island, VA.

Currently set to launch on Jan. 11, 2003, ICESat will map the Earth's ice sheets using a radar-like system called lidar. Short for "LIght Detection And Ranging," lidar measures the time it takes for light to reflect off the surface of an object. In this case, The Geoscience Laser Altimetry System (GLAS), the lidar system of the ICESat satellite, will measure the size of ice sheets in the polar regions to determine if they are growing or shrinking. If the ice sheets are shrinking, then melting ice might cause global sea levels to rise over time, and ICESat will attempt to gauge the extent of such effects.

To make sure ICESat's lidar system is calibrated properly, NASA will have the satellite target a set of test sites during the first three months of orbit. Chief among the duties of Csatho and her colleagues is choosing and characterizing some of these calibration sites.

One site is the McMurdo Dry Valleys, the largest ice-free area in Antarctica. The Dry Valleys make a good test site, Csatho said, because the area's proximity to McMurdo Station allowed researchers to collect precise surface elevation data by using NASA's Airborne Topographic Mapper, a scanning lidar system. Those results can be compared to ICESat's data to see how well the new lidar system is working.

The Dry Valleys area presents special challenges for lidar measurements, Csatho explained. There, the exposed rock is very dark, and the ice is very bright. That huge change in brightness can cause the lidar system to make errors in measurement.

That's what makes the Ohio State lidar mapping software ideal for the job. Tony Schenk, professor of civil and environmental engineering and geodetic science, first developed the software that fuses lidar data and aerial imagery to automatically map areas of complex shape and elevation, such as roads or cities. Impeyong Lee, a postdoctoral researcher at BPRC, is helping Schenk adapt the software code for ICESat.

Tests in Ocean City in 2001 revealed that the software performed well at mapping a complex city skyline, Lee said. As seen from above, the up-and-down surface of roofs of varying heights presents the same challenges as the bright and dark areas of the Dry Valleys.

Yushin Ahn, one of Schenk's doctoral students, and Marcus Dora, a visiting graduate student in cartography from the University of Dresden in Germany, will create the maps that NASA scientists and others will use to study the data in the future.

As ICESat begins to take its measurements, the Ohio State team will help calibrate GLAS. Csathos' laboratory will host one of the space agency's remote computing facilities for the mission, which means the researchers will be responsible for testing new data processing ideas, and will work closely with NASA throughout the mission. NASA has assigned several other research groups around the country to similar tasks, so it can compare all the results before making mission decisions.

Turning numerical satellite data into high-quality information, such as geophysical parameters of the surface, isn't computationally intensive so much as data intensive, Csatho explained.

"The data comes in from the satellite as photons received per unit time -- that's it," she said. "So our processing has to make that data useful to people. That's what's exciting about this project. We start out with points and numbers, then the data goes through various kinds of processing and we end up with a wonderful map."

Other Ohio State team members also include David Bromwich, senior research scientist at BPRC and associate professor of geography, and Kees van der Veen, research scientist at BPRC. The two will help process and interpret the ICESat data as it comes in.

Ohio State is especially suited to contribute to ICESat, van der Veen said, because of the breadth of expertise and history of collaboration at BPRC. "We have experts in satellite processing as well as data interpretation," he said. "Most facilities only have one or the other, or have little communication between the two groups."

Van der Veen eagerly awaits the ICESat data. "From my perspective, the question is, what are the ice sheets doing? Are they getting bigger or smaller? Once we know that, we can combine the ICESat data with other data to figure out why changes are happening, and whether they are part of larger trends. Ultimately, that's the Holy Grail of glaciology -- to be able to predict whats going to happen in the future."

Given the public interest in global climate change, the group plans various outreach activities throughout the mission. Most recently, Ohio State hosted a three-day tutorial followed by a workshop on laser altimetry for scientists, educators, and students.