DOD taps NASA for charting mission

The armed services and the scientific community will have access to a previously unavailable wealth of topographic data as a result of a cooperative agreement inked last month by the Defense Mapping Agency and NASA.

Under a memorandum of understanding signed by the two agencies, NASA will launch the Shuttle Radar Topography Mission (SRTM) in the Year 2000 to collect terrain elevation data for 80 percent of the Earth's surface - all at a new level of resolution and accuracy.

DMA defined the product requirements to meet Defense Department needs, but the information will be a boon for a much larger audience, NASA officials said.

"The scientific community has been dying to get their hands on this," said Earnest Paylor, a geology program scientist at NASA headquarters in Washington, D.C. "This will give us a leg up on being able to analyze the terrain."

With the new data set, DMA, which provides topographic information that goes into everything from mission planning to modeling and simulation exercises, will be able to provide much more detailed information to its DOD customers. DMA also plans to use the NASA-collected data internally to create image-based maps with elevation information, according to Paul Shalomonowiz, a physical scientist at DMA.

In particular, the terrain data will be important for researchers involved in Mission to Planet Earth, a key NASA program to study the earth's atmosphere with a focus on global changes.

DMA began SRTM because of a joint-services requirement to provide terrain data in 30-meter increments, Shalomonowiz said. DMA's current data set, which covers only 65 percent of the world, has a resolution of 100 meters.

DMA looked at a number of solutions for meeting the joint-services requirement, but "the proposal put in by NASA was, in fact, clearly the best solution as far as a timely way of acquiring data," Shalomonowiz said. Under that plan, SRTM will carry the Spaceborne Imaging Radar-C, which was carried by the Shuttle Endeavour in 1994. However, NASA will add a 60-meter mast, to which it will attach an additional antenna and improved tracking and navigation devices. The second antenna will make it possible to translate the radar signals into 3-D elevation data.

DMA traditionally gathered terrain information by using stereo photography, in which people, and later computers, worked with overlapping terrain images and a stereo plotter to interpolate elevation data.

This process took DMA roughly 20 years to produce its current 100-meter data set. The arduous task was made more difficult because of frequent cloud cover in some areas of the world, such as the equator.

SRTM, by contrast, will generate the 30-meter data set in about a year. Once the 11-day mission is complete, NASA's Jet Propulsion Lab will take about three months to verify and clean up the estimated 19 terabits of data. About another nine months later, the data will be processed using supercomputer technology, NASA said.

The end product will be a mosaic of digital global terrain elevation strip maps covering about 80 percent of the globe and 95 percent of the earth's population, according to NASA.

This data will be of immeasurable value to NASA and its broad array of researchers, said Dick Munson, NASA's SRTM program manager. "It is fundamentally a tool that enhances any other ground-oriented science studies," Munson said.