NASA’s plan to seek bids this autumn for a land-imaging satellite to replace a pair of old and ailing Landsat spacecraft is in doubt due to objections raised by one of the U.S. space agency’s key Senate supporters. Scientists say this latest twist in the Landsat saga has increased the likelihood of a major break in a data record that today spans some 30 years.

Sen. Barbara Mikulski (D-Md.) says she disagrees with NASA’s plan to award a single, fixed-price contract for the so-called Landsat Data Continuity Mission and has asked the agency to suspend the procurement for now.

That edict was included in report language accompanying the 2007 Commerce, Justice, Science spending bill approved July 13 by the Senate Appropriations Committee. Warning that NASA will get no money for the Landsat Data Continuity Mission in 2007 if it continues on its current acquisition path, the report directs NASA to “suspend any further procurement activity” until Congress gives final approval to the spending bill, something that is not expected to happen before November.

In a statement provided to Space News, Mikulski, the ranking Democrat on the appropriations subcommittee that drafted the bill, characterized NASA’s procurement model as “fundamentally flawed” and said it “does not guarantee real competition or true government oversight.”

“I want to see more competition in science missions, not less,” Mikulski said in the statement. “NASA’s most successful Earth science missions — including Landsat 7, Aqua, and Terra — all used a procurement model that fully competed individual segments with NASA serving as project integrator. These missions came in on time, generally on budget and accomplished their scientific objectives. Real competition has always proven the best value for the taxpayer and for NASA. I want to keep it that way.”

The Landsat 7, Terra and Aqua programs were managed by NASA’s Goddard Space Flight Center in Greenbelt, Md.

While the Landsat language in the appropriations report lacks the force of law, NASA observers said the agency must try to reach some sort of accommodation with Mikulski, or risk alienating a key political champion and annoying the Senate Appropriations Committee. At press time, a small NASA-led delegation was due to visit Mikulski’s office the week of July 24 to discuss the matter.

NASA, meanwhile, would not say what it intends to do in response to the report language .

“Legislative deliberations are very dynamic and appropriations language can evolve and change during that process. The impact of the present language is under review,” Ted Hammer, acting associate flight programs director in NASA’s Science Mission Directorate, said in a written statement.

NASA has been working all year on a solicitation calling for delivery of a fully integrated Landsat satellite at a fixed price, and was on track to release a draft request for proposals in September when Mikulski’s de facto stop-work order was issued — with little advance warning .

The U.S. government has continuously collected moderate-resolution imagery of the Earth’s land masses since the Landsat program began in the early 1970s. But despite a 1992 law committing the U.S. government to ensuring the continuous collection of Landsat-type imagery, the program has been on shaky ground since a NASA-led effort to privatize the program fell through in 2003. The White House Office of Science and Technology Policy responded by brokering an interagency agreement to include a Landsat-type sensor on the National Polar-orbiting Operational Environmental Satellite System, or NPOESS, then due to start launching around the end of the decade. However, after it became clear the NPOESS program was headed for trouble, the White House reversed course, directing NASA in December to acquire a complete satellite to replace the increasingly creaky Landsat 5 and 7 satellites as soon as possible.

Landsat proponents are concerned that Mikulski’s protest could seriously delay the Landsat procurement and increase the likelihood of a gap in the collection of land imagery. Neither Landsat 5 nor Landsat 7 is expected to last beyond the end of the decade, and NASA has been telling prospective bidders for the follow-on mission that it is willing to pay a premium to have the new satellite on orbit before 2011.

James Plasker, executive director of the Bethesda, Md.-based American Society for Photogrammetry and Remote Sensing, said the latest turn of events is “very worrisome” for Landsat users, many of whom say they already are feeling the effects of a Landsat gap because Landsat 7 has been returning degraded data for the last three years.

“Anything that is done to delay [the follow-on mission] only exacerbates the data gap,” Plasker said,

Kass Green, a Berkeley, Calif.-based remote sensing consultant and former president of Space Imaging Solutions , also expressed frustration with the Senate Appropriations Committee’s intervention.

“The U.S. government has screwed up this follow-on [mission] for several years now and this is just one more thing to delay it when you’ve got worldwide needs,” Green said. “The gap is already here, it’s going to get worse, and we can’t afford this stuff.”

Green said she did not see the committee’s problem with using a fixed-price contract to buy a single-sensor, operational satellite like Landsat.

“What’s wrong with a firm fixed-price contract? Why is that not the best choice for the taxpayer?” Green asked. “I understand going cost-plus when you have a lot of new technology to deal with, but we are talking about an operational program here, not cutting-edge technology.”

Green and Plasker said that while they could only guess at Mikulski’s motivations in holding up the Landsat acquisition, the increased government oversight called for by the senator would almost certainly translate into more work for Goddard .

“Given that [Mikulski’s] been a very strong supporter of Goddard — and indeed this program – the language sounds like, ‘you took this out of Goddard’s hands and we want to see it come back there,’” Plasker said. “I don’t know if it’s true or not. I hope it’s not.”

Green said that, at least from the outside, it looks like “infighting at NASA” also has come into play.

“It’s so frustrating that after we have had failure after failure to get [the Landsat Data Continuity Mission] going and now, after we were getting so close, to have this come up,” Green said. “From the outside, it is incredibly frustrating to see how our government deals with such a valued resource.”