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Moderate-resolution imagery seen as important tool

The White House plans to deepen its commitment to the nation’s space-based land-imaging program, it said in a report last month.

The report, titled “A Plan for a U.S. National Land Imaging Program,” makes recommendations for the continuation of Landsat, the satellite-based Earth-imaging program that has provided millions of moderate-resolution images since 1972. The report was issued by the Office of Science and Technology Policy, the arm of the White House that advises the president on matters of science and technology. OSTP is also responsible for articulating the president’s science and technology programs.

Leadership role

The plan reflects the White House commitment to take more of a leadership role in understanding the changes in the land surface observed worldwide, said John Marburger, science adviser to the president and director of OSTP.

“The land surface, polar regions and coastal zones are undergoing significant changes under the pressures of population growth, development and climate change, and we must carefully monitor these changes in order to manage them,” he said. “The importance of this imagery to the nation requires a more sustainable effort to ensure that land-imaging data are available far into the future.”

The report made three main recommendations. The United States should:

  • Commit to continue the collection of moderate-resolution land imagery.
  • Establish and maintain a core operational capability to collect moderate-resolution land imagery through the procurement and launch of a series of U.S.-owned satellites.
  • Establish the National Land Imaging Program, hosted and managed by the Interior Department, to meet its civil land imaging needs.

Landsat’s moderate-resolution imagery data is used by the Agriculture, Commerce, Defense, Energy, Homeland Security, Interior, Justice, State, and Transportation departments; NASA; and the National Science Foundation in addition to other nations including China, India, Japan and Russia.

Landsat data has been used as an early-warning system to detect famine in Africa, for land-use planning and water management, and for national security operations. Moderate-resolution satellite imagery is used to get images of larger areas of land, said Ray Byrnes, liaison for satellite missions at the U.S. Geological Survey and one of the authors of the report.

High-resolution satellite imagery can take a shot of Washington, D.C., and show all the buildings on the Mall.

But to get a snapshot of the entire Chesapeake Bay would require the use of Landsat, which would take several days to get high-resolution images of the bay. Landsat’s moderate-resolution imagery can take photos of the whole globe several times a year. “High-resolution satellites aren’t designed to do that,” Byrnes said.

Despite Landsat’s long history and usefulness, the United States has never established it as an operational program as it has other space-based observation programs, such as weather forecasting.

NASA has handled Landsat’s research and development side, Byrnes said. Landsat’s management is shared by several agencies, including USGS and NASA. “But no has been able to take ownership of it and make it operational. No one agency has championed the cause.”

The federal government has twice tried to commercialize the program, but neither attempt succeeded.

With one agency, the Interior Department, at the helm of Landsat, the program stands a better chance of continuing into the future, the report stated. The moderate-resolution imaging program should be treated more like weather or navigation satellite programs, Byrnes said.

“It would be awfully troubling if the National Weather Service said, ‘Our satellites are coming down, and it will be two or three more years until we have a weather satellite,’ ” he added.

But that’s what is happening with Landsat.

Both Landsat 5 and Landsat 7 are aging and not necessarily gracefully. Landsat 5 was launched in 1984 and Landsat 7 in 1999, and both have overstayed their welcome in the starry skies above.

On borrowed time

“Landsat 5 is way beyond its design life,” Byrnes said. It carried an extra-large fuel tank, which has allowed engineers to keep repositioning it.

Although satellites seem to whirl magically through space in their orbits around the Earth, they all carry fuel and small thrusters, Byrnes said. “As the orbit degrades a little bit over the years, you’re constantly readjusting it.”

If the satellites’ sensors and key subsystems hold up, they could last a few more years.

“But once you’re out of fuel, you can’t maintain your orbit position. You need enough fuel to bring them down for a gradual re-entry,” he said.

Neither satellite is expected to operate beyond 2010.

A successor, the Landsat Data Continuity Mission, is scheduled for launch in 2011. But even if the government does take immediate action, the program will suffer a gap in data.

The country still has no national program that includes plans for a successor to LDCM or deployment of a replacement satellite if LDCM should fail at launch or early in its design life.