WASHINGTON — NASA and U.S. lawmakers are at odds over whether a 2009 budget increase for the agency’s $5 billion James Webb Space Telescope, the bulk of which was provided as part of last year’s economic stimulus package, constitutes a cost overrun on the program.

In the report accompanying an omnibus U.S. federal spending package for 2010 that includes NASA funding, which passed in December, Congress criticized the program for spending some $95 million more than was budgeted for 2009. The language, inserted by Sen. Barbara Mikulski (D-Md.), who chairs the Senate Appropriations commerce, justice, science subcommittee, indicated that additional cost overruns on Webb loom in 2010.

Jon Morse, director of astrophysics at NASA’s Goddard Space Flight Center, said the bulk of last year’s excess spending on the flagship-class observatory, $75 million in 2009 American Recovery and Reinvestment Act funds, was needed to keep the program’s workers employed. “There’s no question that if we had not had an injection of those funds that we would have had to lay off a couple hundred at least — we would have had to slow down work,” he said. He added that program officials became aware of the budget shortfall when an independent review board drew attention to it during Webb’s mission confirmation review in 2008.

“That adjustment was made in order to achieve the budget profile that the standing review board recommended, and we could not have gotten there without that stimulus money,” he said, adding “there was a good six months between the review and when we were actually able to start thinking about making that adjustment.”

Morse said the near-term cash infusion will reduce the chances of future cost growth on the program. “The cheapest [James Webb Space Telescope] is the one that launches the soonest,” Morse said. “Because if you slip work you wind up paying a price for that; not just inflation but you have an inefficiency in the way you use your work force and you wind up paying two or three times the amount that you slipped, so we’re really trying to hold schedule.”

Injecting resources “here and there” as needed is the best way to do that, he said, adding that the stimulus funding will not add to the overall cost of the program.

A Senate aide was not buying that argument, however, and said Webb telescope program officials need to level with lawmakers about cost overruns.

“If a program has a certain amount budgeted and it needs more money, that’s an overrun,” the aide said. “We appropriate one year at a time, so when you have an overrun in one year, and you have to cover it, it’s taking from other priorities.”

The Senate aide said program officials have yet to provide a satisfactory accounting of the program’s 2009 spending, and that the stimulus request for Webb prime contractor Northrop Grumman Corp. of Los Angeles came out of nowhere.

“This time last year when we were talking to NASA, Webb wasn’t even on the list” of economic stimulus projects, the Senate aide said.

Morse acknowledged that the program has suffered technical and fiscal challenges, including an anticipated three-month delay in work on the telescope’s primary mirror. He added that NASA will request additional adjustments as needed to keep the observatory’s 2014 launch date on track.

“This is the challenge of being on the scientific frontier,” Morse said. “You’re developing capabilities for the first time. We’re not talking about doing eight [James Webb Space Telescopes] where you get economies-of-scale; this was a unique observatory to do specific science goals.”

With Webb consuming some 42 percent of NASA’s 2010 budget for astrophysics, Morse said he is dedicated to getting “the right plan in place for the telescope.” Working in Webb’s favor, Morse said, is the fact that the program’s requirements have remained stable since 2005.

“We are working toward specifications that are well known across the observatory,” he said. “I’m optimistic that if we don’t quite have it, we’re darn close.”