While NASA fared better than many federal agencies in U.S. President George W. Bush's 2006 budget request, the White House is not seeking as much money for the U.S. space agency as previously planned.

The White House is seeking $16.45 billion for NASA in the 2006 budget. That's an increase of 2.4 percent over what the U.S. space agency has in its 2005 budget, but still about $500 million less than what the agency had been expecting.

When Bush gave NASA a new space exploration vision last year, he also pledged to help pay for it with three straight years of roughly 5 percent budget increases. Bush -- with help from House Majority Leader Tom DeLay (R-Texas) -- delivered on that promise for 2005, but his 2006 request forecasts much more modest increases through the end of the decade.

NASA's 2006 budget request, which is headed to Congress Feb. 7, keeps many of the agency's space exploration goals on track, but a number of high-profile efforts have been canceled, postponed or scaled back.

The biggest casualty of NASA's latest budget request is the Jupiter Icy Moons Orbiter (JIMO) mission, which is effectively canceled in the 2006 request. NASA had planned to launch the multi-billion dollar probe around 2015 as the Project Prometheus nuclear power and propulsion initiative's flagship demonstration.

NASA officials now say JIMO is too ambitious an undertaking for an initial demonstration, and a search for an alternative mission is underway. NASA is still requesting $320 million to continue nuclear power and propulsion work in 2006, but that is substantially lower than the roughly $500 million the agency had planned to spend based on last year's five-year budget projection.

NASA also has trimmed its request for Project Constellation, which is intended to develop a Crew Exploration Vehicle that can transport astronauts to the Moon.

NASA Comptroller Steven Isakowitz, briefing reporters ahead of the formal budget release, said the $1.1 billion the agency is seeking is enough to keep development of the Crew Exploration Vehicle on track for a 2014 delivery. He said NASA still intends to award at least two design contracts later this year and hold a 2008 fly-off that will determine who gets the contract to build the multi-billion dollar vehicle.

Spending on the space shuttle program is expected to drop to $4.3 billion in 2006 after topping out at $5 billion this year. That $5 billion figure includes $760 million tied to improvements made in the wake of the February 2003 Columbia accident. Still, NASA's 2006 request for the shuttle program is about $200 million higher than what the agency had previously forecast.

NASA's budget request includes no money for any type of Hubble Space Telescope servicing mission, as first reported by Space News. Instead NASA is seeking $75 million to continue development of a deorbit mission the agency needs to launch around the end of the decade to steer the giant telescope safely into the ocean once it is no longer capable of doing science. The agency also is asking for an additional $20 million to investigate ways short of launching a space shuttle or robotic repair mission to keep the telescope in service as long as possible. Hubble is expected to go dark in 2007 or 2008 as critical components fail.