Scientists who rely on Landsat imagery applauded the White House decision to build and launch a dedicated new land observation satellite, but still worry that the current Landsat 7 spacecraft will not last until its replacement is safely on orbit.

The White House Office of Science and Technology Policy issued a memo Dec. 23 stating the administration’s intent to construct a free-flying Landsat satellite. Previous plans called for adding a Landsat-type camera to the National Polar-orbiting Operational Environmental Satellite System (NPOESS), a new generation of weather satellites whose projected costs have soared .

“I think there’s no question this had to happen,” said Samuel Goward, a geography professor at the University of Maryland in College Park who co-chairs the National Satellite Land Remote Sensing Data Archive Advisory Committee. “The problems with NPOESS were growing so big it was almost impossible not to move in this direction.”

But Goward is concerned that the change of plans may be too late to avert a multi year break in Landsat imagery collection, threatening an uninterrupted photographic record spanning more than three decades of natural and human-induced changes to the Earth’s land surface.

“My guess is that we’re probably going to see the failure of Landsats 5 and 7 in the next year or two years. It’s going to take a few years to procure the new mission. It looks like it’s a multi year data gap we’re facing,” Goward said. “And some people already have a gap,” he said, referring to the fact that Landsat 7 has been returning degraded imagery since its main instrument malfunctioned in 2003.

Landsat 5, meanwhile, has been out of service since November when its back-up solar array drive began behaving erratically , preventing the 20-year-old satellite from keeping its arrays constantly facing the Sun.

Jay Feuquay , director of the Land Remote Sensing program of the U.S. Geological Survey , which has management responsibility for Landsat , said Jan. 4 the flight team has been testing a new operating scheme that should enable Landsat 5 to resume operations by the end of February. Some initial test imaging was planned for the week of Jan. 12 , he said.

“We remain optimistic we’ll be able to do more than a token return to operation, that we’ll be able to, if not fully, at least substantially resume operations,” Feuquay said.

Given the probability that both of the current Landsat spacecraft will cease operating sometime during the two to three years it likely will take to build a replacement satellite, Landsat users are bracing for a potentially lengthy data gap.

Kass Green, president of the Alta Vista Co., a Berkeley, Calif.-based firm which provides information products derived from remote sensing imagery, said there are other sources of imagery, such as European and Indian Earth observation satellites. “But it’s really upsetting,” she said of the Landsat situation. “I’ve got clients that are not going to pay that kind of money, even government clients.”

Goward said foreign satellites can help cushion the blow of not having a healthy Landsat spacecraft operating, but cautioned that these alternatives are less than ideal. He added that ” there are lots of uncertainties on whether we’d be able to get the observations we need for global and regional studies.”

Despite the looming gap, Green said the White House decision to launch a dedicated satellite has brought sighs of relief from a user community grown accustomed to low-cost Landsat data provided by the U.S. government. “People have started to do so much with Landsat data. Once it became a public good again, computers got faster, and we got much better software to process the data,” she said. “Once that all came together, we started to see a huge increase in both private and government usage, and then you get NASA starting to back away from it, and its funding in trouble. It was a difficult year to go through, but I’m really, really happy with this commitment.”

Green, along with Kurt Allen, president of the Management Association for Private Photogrammetric Surveyors , also applauded the fact that the White House memo addresses the issue of long-term Landsat data continuity. “It remains the goal of the U.S. government to transition the Landsat program from a series of independently planned missions to a sustained operational program funded and managed by a U.S. Government operational agency or agencies, international consortium, and/or commercial partnership,” the memo said.

“We’re really happy that [the Office of Science and Technology Policy] directed the [National Science and Technology] council to coordinate a long-term plan for imaging,” Allen said. “I think that’s going to be an important roadmap for the future, and hopefully the White House will also see the geospatial community is speaking with one voice.”

But Goward thinks the memo’s wording still leaves things uncertain.

“It’s basically saying that we have to somehow figure out how to make an operational system,” Goward said. “That’s open-ended. I worry whether this could leave us in the same situation we’ve been in for 30 years … everything ultimately becomes associated with dollars — who’s going to get the budget authority to execute such an operational system? It does need to be addressed.”