This story was updated at 3:34 p.m. EST.
WASHINGTON - The White House's $17.3billion request for NASA in 2008 demonstrates U.S. President George W. Bush'scommitment to replacing the spaceshuttle by 2014, but might not be enough to offset the impact of alower-than-expected budget for this year, agency officials said.
"This increase demonstrates thePresident's commitment to NASA and to maintaining our nation's leadership inspace and aeronautics research," NASA chief Michael Griffin said in a Mondaybriefing.
The request, which would give thespace agency a raise of roughly $1 billion over this year's likely budget,keeps science and aeronautics spending relatively flat, but does include fundsto begin purchasing a new series of data-relay spacecraft.
The annual budget request tracksvery closely with the spending plan the White House sent to Congress this timelast year, which sought 3 percent increases for NASA in both 2007 and 2008. However, NASAis unlikely to get a raise this year due to a plan by the Democratic-ledCongress to fund most U.S. domestic federal agencies at their 2006 levels.
"The key message we have with thisbudget is the agency is on track," NASA Comptroller David Schurrtold reporters Feb. 2 during a budget briefing at agency headquarters here. "Weare making progress toward the vision ... there are no real strategic changes inthis request."
However, Schurrand NASA's director of strategic investments, Chris Shank, said progress on theshuttle replacement effort is threatened by NASA's likely budget for 2007.
Congress adjourned last year withoutfinishing nine of 11 annual spending bills, among them the one that funds NASA.The new Congress has decided to fund most government agencies, including NASA,at their 2006 levels rather than spend time trying to pass the unfinished spendingbills.
The House passed a broad spendingmeasure Jan. 31 that would fund NASA at $16.2 billion this year, Fiscal Year2007 (FY07) denying the agency any increase even as it seeks to ramp upspending on its space shuttle replacement. The Senate is expected to pass themeasure by mid-February.
"The FY07 appropriations,if enacted as the House has resolved, will jeopardize our ability to transitionsafely and efficiently from the shuttle to the Orion Crew ExplorationVehicle and the AresI Crew Launch Vehicle," Griffin said. "It will have serious effects on people,projects, and programs this year and for the longer term."
NASA officials said the spendingmeasure endangersthe agency's plans to field the OrionCrew Exploration Vehicle and AresI rocket by 2014.
"If we donot quickly come to grips with this issue, we may have a prolonged gap betweenthe end of the shuttle program and the beginning of the operational capability ofour new systems," Griffin said.
NASA plans to retire its three agingspace shuttles in September 2010 following the completion of the International SpaceStation.
"Naturally there are going to bechallenges with the  appropriation and that threatens our progress,"Shank said last week. "But this  budget, with a 3.1 percent increase,really does demonstrate that we've got the commitment and the resources tocarry off a lot of these challenges."
Under the 2008 plan, spending on Earthscience satellites, planetaryprobes and other unmanned science craft would remain flat at $5.5 billionthrough the end of the decade so that NASA can complete the International SpaceStation and build a new crew capsule and expendable rocket to replace thespace shuttle after it retires in 2010.
Funding for aeronautics researchalso would remain flat, although a change in the way NASA accounts for overheadexpenses makes it appear that aeronautics is in for a big budget cut.
The budget request includes $554million for aeronautics for 2008, down $170 million from the agency's $724.4million request for 2007. NASA officials, however, said that if the newagency-wide overhead rate was in use last year, the 2007 request would havebeen $529.3 million so the agency is actually seeking a modest increase foraeronautics.
NASA informed Congress lastSeptember that it would be simplifying the way it calculates overhead andadministrative costs in part to ensure that its 10 regional field centers cancompete for internal projects on a level playing field. The change wasnecessary, agency officials said, because the smaller centers tend to have higherper-capita overhead costs.
Because all parts of NASA's budgethave been affected by these accounting changes, year-to-year comparisons aremade that much more complicated.
Under the request, NASA'sExploration Systems budget would climb to $3.9 billion in 2008 and reach $4.7billion in 2010 before making a big jump to $8.7 billion in 2011, the firstyear NASA expects to be unburdened by the space shuttle's hefty annual tab.
NASA's Science Mission Directoratealso is projected to benefit from the shuttle's retirement, although not until2012. That is when NASA and the White House foresee being able to afford 2.4percent increases for the science mission portfolio.
For 2008, NASA science spendingwould grow about 1 percent to $5.5 billion, a sum that includes nearly $1.4billion for planetary science, $1.6 billion for astrophysics, $1 billion for heliophysics, and $1.5 billion for Earth science.
NASA's Space Operations MissionDirectorate, which runs the space shuttle and international space station programs,would receive $6.8 billion for 2008, a significant increase over the likely2007 budget. Part of the increase is needed for new satellites NASA expects toorder later this year to replace the Tracking and Data Relay Satellite Systemthat NASA and the U.S. military use to communicate with Earth-orbitingspacecraft.
SPACE.com staff writer Tariq Malik contributed to this report from New York City.