NASA’s 2006 spending plan is nearing final approval by the U.S. Congress, but the House and Senate must still reconcile some key differences between their versions of the NASA budget before the space agency gets any of its new money for the year.

NASA requested $16.456 billion in February for the 2006 fiscal year that officially starts Oct. 1, and both the House of Representatives and the Senate have voted to give NASA roughly that amount. But the House and Senate are at odds about how NASA should spend some of that money in the year ahead.

The House came closest to honoring NASA’s request, approving June 16 a spending bill that would give NASA about $15 million more than it is seeking, but would require NASA to spend nearly $200 million on efforts the agency no longer considers priorities.

The Senate approved its version of the NASA spending bill Sept. 16, trimming about $60 million off the top of the agency’s budget and requiring the agency to reprioritize more than $500 million in spending to fund NASA projects considered important by lawmakers.

The two spending bills now head to a House and Senate conference where a delegation of lawmakers must iron out all differences between the competing legislation and produce a joint bill, called a conference report. The House and Senate must then vote again to approve the conference report before it can be forwarded to the White House to be signed into law by the president.

While the House and Senate both so far have approved spending bills that would increase NASA’s budget by at least $200 million over the 2005 level, Washington-based space policy analysts caution that NASA could end up seeing its budget cut this year as lawmakers look for ways to finance the reconstruction of the U.S. Gulf Coast in the wake of hurricanes Katrina and Rita.

The White House already has objected to some of the provisions in the Senate bill, among them the elimination of all requested funding for NASA’s recently established Centennial Challenges prize competition program.

The Senate also declined to provide any of the $160 million NASA requested for buying international space station cargo delivery services from U.S. companies or abroad, reasoning that NASA has not spent any of the $98 million Congress approved for that purpose for 2005.

“This funding is sufficient for any initial activity that might be initiated for this activity in fiscal year 2006,” the Senate wrote in the report accompanying its spending bill. The Senate report gave similar reasons for zeroing NASA’s $34 million Centennial Challenges request.

NASA sees the Centennial Challenges program as a low-cost means of stimulating technological innovation and has already announced several competitions.

The Senate’s inclusion of an extra $250 million to help fund a space shuttle mission to service the Hubble Space Telescope also has drawn White House complaints. In a Sept. 8 memorandum to the Senate’s two top Republican and Democratic appropriators, the White House Office of Management and Budget noted that the administration “strongly objects to a total of nearly $600 million in earmarked funding for unrequested activities, including $220 million above the President’s request for a possible Hubble servicing mission, which would significantly reduce the resources needed for critical ongoing and planned science and technology efforts.” By the time the bill cleared the Senate a week later, however, the extra Hubble funding had been increased to $250 million.

In addition to the extra Hubble money, the Senate added $50 million for various unspecified projects canceled by NASA, $25 million to breathe new life into the X-43 hypersonic engine flight test program, $15 million for the Earth Science Applications Program and $30 million for advanced materials research.

The House also engaged in its share of earmarking, directing NASA to spend an additional $54 million on aeronautics research, effectively reversing the cuts the agency intended, and $30 million to resurrect the canceled Glory greenhouse gas-measuring mission. House lawmakers also added $10 million for the Space Interferometry Mission and $2 million for education programs.

To help pay for these increases, the House voted to cut NASA’s $1.8 billion space station request by $10 million, the space station crew and cargo services account by another $10 million, and a total of $30 million from rocket propulsion testing, space communications and the agency’s launch services procurement budgets.