ADELPHI, Md. — NASA Administrator Mike Griffin is sparring with the authors of a 10-year plan for Earth science research over the cost estimates for 17 missions the report recommends that the agency undertake.

Griffin, speaking March 20 at the 45th annual Robert H. Goddard Memorial Symposium here, fired the opening shots when he criticized the estimates as unrealistically low and pointed out that they were drafted by interested parties — namely, agency managers that would run the missions. Officials with the National Research Council, which drafted the report, fired back, saying the cost estimates in fact came from NASA and in at least some cases were the result of detailed analysis.

The report “Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, ” was prepared by the National Research Council’s Space Studies Board and released late January . Half of the proposed missions, the report estimates, could be accomplished for $300 million or less, with none costing more than $800 million in today’s dollars.

Griffin said some of the survey’s cost estimates are “off the mark by a factor of two or more.”

Overly optimistic cost estimates are endemic to a decadal survey process that relies heavily on project advocates who “provide optimistic cost estimates, enhancing the odds that their project will be seen favorably by [National Research Council] reviewers,” he said.

Griffin said inaccurate cost estimates in decadal surveys are “a self-inflicted problem within the space community that affects the credibility of all of us.

Marcia Smith, director of the National Research Council’s Space Studies Board, told attendees of the Goddard Symposium the next day that the cost figures “came from NASA, so those are NASA estimates.”

Art Charo, the National Research Council staff member who directed the Earth science survey, clarified in a March 22 telephone interview that the estimates were developed in consultation with NASA scientists and engineers at the Pasadena, Calif.-based Jet Propulsion Laboratory and the Greenbelt, Md.-based Goddard Space Flight Center.

Charo said that the decadal survey panel, if anything, attempted to err on the side of caution.

“The notion that these estimates are off by a factor of two cannot be correct,” Charo said, noting that many of the near -term proposed missions have been studied fairly in depth by NASA and rely on mostly very mature technologies. “Some of the costs for missions recommended for starts in [the] latter part of the coming decade do have greater uncertainty, especially involving technology that is currently at a relatively low” readiness level .

Charo also noted that the survey presented the cost estimates with the caveat that they were thought to be accurate within plus or minus 30 percent.

Griffin acknowledged in his speech that NASA field center personnel played a role in producing the cost estimates, but emphasized that agency headquarters, by design, has no involvement in the survey process. So the National Research Council , he said, gets cost information from principal investigators and project managers who have a stake in the mission they are evaluating . “I’m sure you will be shocked — shocked — to hear that the people involved are not completely disinterested with regard to the status of their particular mission proposal,” he said.

Previous decadal surveys have significantly underestimated the cost of proposed missions, frustrating scientists when NASA cannot afford to accomplish everything on the wish list. Astronomers have acknowledged that the 2001 decadal survey for astronomy and astrophysics underestimated the cost of the James Webb Space Telescope and Laser Interferometer Space Antenna, with some suggesting that the next 10-year plan classify missions as small, medium and large rather than pin a price tag on each one .

Smith, in a brief interview at the Goddard Symposium, acknowledged the difficulty of producing credible cost estimates within the constraints of a decadal survey and said the Space Studies Board should be given the time and budget for seeking outside estimates. For example, a Space Studies Board panel due to recommend by September which so-called Beyond Einstein fundamental physics mission NASA should undertake first has hired SAIC, the San Diego-based technical consulting firm, to produce cost estimates for the candidate missions, she said.

Griffin also believes cost estimating is better left to professionals without a stake in the outcome, and recommended that future decadal surveys use NASA’s Program Analysis and Evaluation (PA&E) office to prepare more realistic cost estimates for proposed missions.

PA&E would prepare a more rigorous cost analysis of any mission NASA might propose to add to its 2009 budget request, but would not do so for all 17 proposed missions, Griffin said.

“I’m not going to go through on a blanket basis and re-cost every mission,” he said. “The mission concepts aren’t well enough defined, and I don’t have the resources available to do that.”

Griffin also took issue with what he characterized as “a rather brazen recommendation” in the survey that NASA spend another $500 million a year on Earth science. “This is a clear attempt to upset the traditional funding boundaries between and among the various scientific portfolios at NASA,” Griffin said. Griffin has faced pointed questioning from Congress this year about how quickly NASA will move to implement the recommendations in the Earth science decadal survey. Griffin has repeatedly told lawmakers in recent weeks that the survey was requested by NASA and would guide decisions about the missions NASA undertakes, but that the agency cannot afford a $500 million budget increase for Earth science.

NASA’s 2007 budget includes slightly more than $1.3 billion for Earth science. The agency’s 2007 request, which was tossed out in favor of a continuing resolution that funds NASA at last year’s level, sought $1.464 billion for Earth science. NASA’s 2008 request, currently before Congress, seeks $1.497 billion for the activity.