WASHINGTON — While confident that the current Landsat satellites can continue operating in orbit until the next generation imager is launched sometime around the end of the decade, U.S. government officials are examining alternative ways to acquire the data.

Landsat users, however, are concerned that the death of plans for a free-flying satellite to gather Landsat imagery could lead to a gap in the collection of the Earth observation data before the new imager becomes operational.

The White House has authorized a plan that will place a Landsat-style instrument on a new generation of U.S. government weather satellites under development. The Operational Land Imager will be placed aboard the U.S. National Polar-orbiting Environmental Satellite System (NPOESS) satellites, but the first of the spacecraft is not scheduled for launch until late 2009.

A committee formed by NASA of people interested in Landsat met Feb. 17 at agency headquarters to identify potential alternative sources of the Earth observation data they now get from two Landsat spacecraft still operating in orbit. The options include forging partnerships with international providers, an official said.

“A lot of us are concerned about” a potential gap, said Samuel Goward, a University of Maryland professor and the Landsat science team leader from 1997-2002. “We’ve been pushing pretty hard on alternative plans. This committee has not been too serious previously, but now it has become very serious. If we hope to continue the archive we have to have something going on.”

The U.S. government has been collecting land remote-sensing data for more than 30 years, but problems with the two existing spacecraft and delays in deciding a course of action for the future have increased the likelihood that the collection could be interrupted.

Landsat 7, suffered a permanent sensor glitch in May 2003 that has degraded the quality in the data, and also has lost one of its three gyroscopes. The 20-year-old Landsat 5 spacecraft also continues to collect data, but its capacity has greatly diminished.

A plan for developing a free-flying satellite that would be in orbit in case the current satellites failed — dubbed the gapfiller satellite by people in the Landsat community — apparently has been scrapped due to schedule and cost concerns.

“The comments we’ve gotten is that it would take NASA until 2008 to put one of these up, and with the NPOESS going up in 2009, the gapfiller was not worth the money,” Goward said. “We find that a little hard to believe. They claim the procurement procedures are slowed up. Given the way things work in NASA, that’s probably true, but none of us are too thrilled about it.”

The time period that concerns users is 2007 through 2010, Goward said.

Richard Marston, a professor at the Oklahoma State University school of geology in Stillwater and vice president of the Association of American Geographers, uses Landsat to study changes in landforms and glaciers over long periods of time, and said he was nervous about the viability of Landsat 7.

A gap in data collection would not be a major problem for his work, but “for others who are monitoring land cover changes, crop yields, etc., a gap could cause serious disruption,” Marston said in a written reply to questions.

Charles Groat, director of the U.S. Geological Survey, which is responsible for collecting and disseminating Landsat data, has said he is confident that Landsat 7, launched in 1999, will operate until the NPOESS launch.

Another official at the survey offered a more blunt assessment. “We’re at the point where we’re going to need some luck to make it,” the official said.

U.S. policy commits the government to ensuring the continuous collection of Landsat data, though it’s hard to determine what the consequences of not fulfilling that requirement would be, officials said.

“Everybody will try their damnedest to keep from having a data gap, because the user community needs it; not because we don’t want to get scolded,” said Ray Byrnes, liaison for satellite programs at the survey. “The data is so important to many people in this country and around the world.”

Since the international community has become reliant on the data, this might be a good opportunity for the U.S. government to forge partnerships to help address the problem, Goward said.

Systems such as the Resourcesat satellites operated by the Indian government, France’s Spot series of spacecraft and the China-Brazil Earth Resource Satellite system can provide “similar but not quite as good data” as 15-meter resolution data collected by the Landsat spacecraft, Goward said.

There will be some technical issues to overcome to create equivalent measurements from data collected by other spacecraft, Goward said. But the U.S. government has made this transition before when the imager aboard the Landsat satellites were improved.

The biggest concern about using international sources of data would be cost, Goward said. Landsat products are provided at the cost of producing the data as required by U.S. law, while other providers may be trying to turn a profit, he said.

“There may be other ways to do this than simply buying data,” Goward said. “Sharing arrangements have been made in the past and could easily happen this time. This would be a nice way to start international cooperation in the Landsat class of observations. There is always the possibility of good things happening in a period of stress.”

NASA officials were not available for comment, spokeswoman Gretchen Cook-Anderson said.

Comments: jbates@space.com