NASA intends to acquire another dedicated Landsat satellite “as soon as possible” to replace the pair of old and ailing land-imaging spacecraft currently on orbit, according to an agency spokeswoman.

NASA expects to lay out before the end of January its schedule for issuing a solicitation, accepting proposals and awarding a contract, spokeswoman Erica Hupp said in a written response to questions.

The White House on Dec. 23 directed NASA to pursue development of a free-flying land-imaging spacecraft, reversing an August 2004 decision to transition the collection of land remote sensing data to the National Polar-orbiting Operational Environmental Satellite System (NPOESS), a series of civil-military weather satellites under development.

Dedicated Landsat spacecraft have gathered medium-resolution land imagery nonstop since the early 1970s. Recognizing the importance of Landsat, the U.S. Congress in 1992 enacted the Land Remote Sensing Policy Act, committing the U.S. government to ensure the long-term continuous collection of Landsat imagery.

After a bid to commercialize the collection of Landsat-type imagery fell through in 2003, the White House brokered an interagency agreement to use the NPOESS satellites to gather the imagery prized by researchers and land-use planners alike.

But in the 16 months since the White House directed NASA to develop a Landsat-type instrument for inclusion on the first NPOESS satellite, cost estimates for building and integrating the sensor have skyrocketed, undermining one of the main arguments against building more dedicated Landsat satellites.

At the same time, the NPOESS program has encountered severe budgetary and technical problems that at minimum threaten plans to begin deploying the satellites at the end of the decade. The program currently is undergoing a congressionally mandated review that in theory could lead to its termination.

The United States currently has two Landsat spacecraft on orbit, but neither is expected to last through the decade. Landsat 5, launched in 1984 , is temporarily out of service while engineers troubleshoot a solar array drive glitch. Landsat 7 has been on orbit since 1999 and suffered a main sensor malfunction in 2003 that has permanently degraded the quality of its data.

With Landsat proponents arguing the NPOESS approach was risky and could lead to a lengthy interruption in the collection of land remote sensing data, the White House agreed last summer to reconsider its 2004 decision.

Under the new policy directive, issued by White House Office of Science and Technology Policy Director John H. Marburger, the Landsat-type imager will be dropped from the NPOESS payload in favor of building a free-flying Landsat spacecraft.

Marburger’s memo, dubbed “Landsat Data Continuity Strategy Adjustment,” does not directly cite the NPOESS problems, instead attributing the policy shift to the technical complexity associated with adding Landsat-type sensors to NPOESS satellites.

NASA discovered last year that the job would be more difficult and expensive than first thought, making “that option less suitable to the goals of both programs,” the memo says.

Under the new plan, according to the memo, NASA will build a dedicated Landsat satellite for the U.S. Geological Survey, a Department of the Interior agency that has a long history of managing the collection and dissemination of Landsat data.

The memo makes clear that the U.S. Geological Survey will be responsible for operating the new Landsat mission and collecting, archiving, processing and distributing its data, continuing the role it has performed in the Landsat 7 era.

Jay Feuquay, director of the Land Remote Sensing Program at the U.S. Geological Survey in Reston, Va., applauded the policy shift as “the right way to go.”

“We are not particularly surprised by the change, as we were part of the team that did some of the preliminary evaluations and made recommendations,” Feuquay said Jan. 4. “This is consistent with our recommendations, and we’re excited to get a decision so that we can start moving forward.”

NASA officials knowledgeable about the Landsat decision were not available for an interview the week of Jan. 2, according to Hupp. In the written responses to questions , NASA said it intended to lay out its Landsat solicitation schedule “in a couple of weeks.”

NASA would not say what it expects to spend on the new mission, noting only that Congress late last year approved spending $338 million for a Landsat data continuity mission. NASA also would not detail the mission requirements beyond saying the satellite needs to be “a free flyer capable of providing Landsat quality data.”

Feuquay also declined to go into much detail about how capable a satellite the government is looking to build.

“I think that we’re hopeful that the [request for proposals] will get some of the best ideas that industry has. We’ll be working with both the industry and user community to ensure they’re well informed, and that we’re getting both the latest requirements and best that the industry has to offer,” he said.

Landsat 7 cost more than $800 million to build and launch. Last year — when NASA was entertaining building a small Landsat-type satellite to bridge any gap between the demise of Landsats 5 and 7 and the launch of the first land imager-equipped NPOESS satellite — the agency challenged industry to come up with a mission design that could be built and launched by 2008 for less than $300 million. At least one company, Ball Aerospace of Boulder, Colo., told NASA it could get the job done for $250 million.

While the new White House direction means NASA will acquire a free-flying land imaging satellite that some future users already are referring to as Landsat 8, it is not a given that there will be a Landsat 9.

Marburger’s memo says it remains the long-term goal of the United States to transition the collection of Landsat imagery “to a sustained operational program funded and managed by a U.S. Government operational agency or agencies, international consortium, and/or commercial partnership.” Although the memo directs an interagency group to come up with such a plan, it does not set a deadline.