WASHINGTON — U.S. President Barack Obama’s NASA budget does not match his campaign promises about the future of the U.S. space program, the chairman of the Senate subcommittee that oversees NASA policy said May 7.

Sen. Bill Nelson (D-Fla) said he expects the budget figures to change after a three-month review of the space agency’s post-space shuttle human spaceflight plans.

Obama’s 2010 budget proposal orders a review of NASA’s plans to replace the space shuttle with new vehicles designed to serve the international space station and eventually carry astronauts to the Moon.

Nelson said the budget, which supports completing nine space shuttle missions before the end of 2010, is a step in the right direction.

“But down the road the administration’s budget does not match what candidate Obama said about the future of our space program. Still, he’s assured me these numbers are subject to change, pending a review he has ordered of NASA,” Nelson, chairman of the Senate Commerce, Science and Transportation science and space subcommittee said in a written statement. “This review, which should be finished in 90 days, is an opportunity to nail down support for human spaceflight.”

The budget proposal endorses flying eight remaining missions before retiring the space shuttle in 2010. An additional mission to deliver the Alpha Magnetic Spectrometer to the space station will be flown “after these flights if it can be safely and affordably completed in calendar year 2010,” according to budget documents released May 7.

But Nelson said he had been assured by Obama that NASA will be allowed to finish “all nine space shuttle missions, regardless of how long it takes.”

All told, Obama is requesting roughly $18.7 billion for NASA for 2010, a 5 percent increase that includes a roughly $150 million budget hike for the Exploration Mission Directorate — the part of NASA in charge of building the Ares 1 rocket and Orion Crew Exploration Vehicle that comprise the early elements of the Moon-bound Constellation program.

Of the nearly $4 billion Obama is requesting for Exploration Systems, $3.5 billion would go to Constellation. While that is nearly $200 million more than Constellation stood to receive next year under former President George W. Bush’s final NASA budget, subsequent budget years are not as generously funded. Obama’s plan calls for spending a total of $16.4 billion on Constellation between 2011 and 2013, or about $3.5 billion less than Bush had planned to spend.

However, as noted in a NASA budget summary posted on the agency’s Web site May 7, the Constellation budget figures are “placeholders” that will be updated following a review “led by an independent, blue-ribbon team of experts.”

Constellation has been the subject of several reports released in recent weeks raising doubt that the program can meet its schedule within the current budget.

Obama’s call for a review of Constellation was praised by the Pasadena, Calif.-based Planetary Society, which previously urged NASA to collaborate with international partners in sending humans to the Moon while focusing human exploration efforts on near Earth asteroids and eventually Mars.

“The independent review may help advance recommendations that The Planetary Society made in its Roadmap to Space,” Lou Friedman, executive director of the Planetary Society said in a written statement. “We have advocated that more international cooperation be incorporated into plans for the human return to the Moon, and this review is a chance to introduce exciting milestones on the road to Mars.”

As widely expected, Obama’s budget includes more money for Earth science than those proposed by his predecessor.

Under Obama’s plan, Earth science would grow at a steady clip during the next five years, eventually topping $1.6 billion in 2014, overtaking planetary science — traditionally the best funded piece of NASA’s science budget.

Aeronautics research is also in for an increase under Obama’s plan, steadily growing from $500 million this year to $536 million in 2014.

Space Operations, the part of NASA’s budget that funds the space shuttle, and international space station, would get a $400 million increase for 2010, rising to nearly $6.2 billion before falling below $3.7 billion as NASA starts to realize savings from retiring the shuttle.