WASHINGTON — The inability of U.S. lawmakers to adopt a spending plan for federal government agencies in 2011 has raised a cloud of uncertainty over NASA’s near-term procurement plans, with some solicitations planned for the budget year that began Oct. 1 being deferred while work on other projects is being scaled back.

NASA, along with the rest of the government, is operating at last year’s spending levels under a continuing resolution the U.S. Congress approved in December. The measure, expected to remain in effect at least through March 4, leaves the agency with about $276 million less to work with than the $19 billion it proposed in the 2011 budget request the White House sent Congress last year.

NASA spokesman Doc Mirelson said new solicitations associated with ongoing programs and projects that are already approved and have adequate funds under the 2010 spending ceiling will move forward as planned.

However, “[i]f budget constraints preclude moving forward on all planned new procurements, the determination of what could be placed on hold will be part of the assessment of funding targets for the year,” he said in a Jan. 20 e-mail, adding that budget uncertainty may result in schedule slips if planned work needs to be adjusted to fit within the funding profile.

One NASA enterprise where huge uncertainty looms is human spaceflight, whose direction has been the subject of a yearlong dispute between the administration of U.S. President Barack Obama and the Congress. NASA is caught between a 2010 appropriations law that forces the agency to continue funding the Moon-bound Constellation program Obama seeks to dismantle, and the recently enacted NASA Authorization Act of 2010 that directs the agency to begin work immediately on a new heavy-lift launch vehicle and crew vehicle for deep space missions while fostering privately developed rockets and spacecraft for astronaut operations in low Earth orbit.

Doug Cooke, NASA associate administrator for exploration systems, said the agency is still reviewing its acquisition strategy for the heavy-lift vehicle and crew capsule. During a Jan. 11 meeting of the NASA Advisory Council’s exploration subcommittee, he said the agency expects to settle on a final design for the heavy-lift vehicle in April and issue a solicitation by May.

However, he said it remains to be seen whether the agency can use existing Constellation contracts — primarily related to the Ares 1 rocket development effort — to pursue the heavy-lifter, the basic design of which was outlined in a report NASA delivered to Congress Jan. 10. The heavy-lift vehicle design includes key Ares 1 components already under contract including the shuttle-derived solid rocket boosters being developed by Minneapolis-based Alliant Techsystems and the J-2X upper-stage engine being built by Pratt & Whitney Rocketdyne of West Palm Beach, Fla.

Rocket hardware builder Aerojet of Sacramento, Calif., which does not have the lead role on any major Ares 1 propulsion systems, is pushing for a full and open competition on the heavy-lift rocket NASA is directed to build.

“We have to go through the discussion on procurement laws and that sort of thing and understand how the requirements map and what we’re doing now to understand what’s possible with existing contracts and what would have to be competed,” Cooke told Space News following the meeting. He added that a heavy-lifter core stage capable of meeting requirements outlined in the 2010 Authorization Act would likely require a competitive selection among industry.

Similarly, Cooke said NASA is still reviewing whether it will have to open a competition for the congressionally mandated Multi Purpose Crew Vehicle. He said NASA’s preferred approach at this point is to continue development of the Orion Crew Exploration Vehicle, which is under contract to Lockheed Martin Space Systems of Denver.

“Right now we actually feel that with the contract in place, we’re on a path that would get us that vehicle,” Cooke said. “We have to validate that through the agency, but we see a pretty direct path on that.”

Cooke also said NASA hopes to award a second round of Commercial Crew Development design contracts in April. “This competition … would run from April of this year to May of 2012 in the end,” he said during the meeting, though he cautioned that NASA is not committed to awarding the funds until Congress appropriates money for the effort.

“We’re looking at what flexibility we have in trying to understand what our constraints are legally,” he said. “But currently the schedule is planned so it would coincide with appropriations.”

NASA’s Earth Sciences Division is also feeling the procurement pinch for some projects. If the continuing resolution is extended for the full year, Earth science programs would receive $1.42 billion, which is some $380 million less than the agency requested.

All flight and nonflight programs funded in 2010 are proceeding, and no launch dates have been slipped for missions that are in the formulation or implementation phase, according to NASA spokesman Stephen Cole.

However, Cole said NASA has deferred plans to ramp up work on a pair of missions that were identified as top priorities by the science community: Deformation, Ecosystem Structure and Dynamics of Ice; and the Climate Absolute Radiance and Refractivity Observatory.

“[W]e are endeavoring to keep the gate review milestones (transition to Formulation) but there is insufficient available funding to prepare fully for, or conduct, the planned ramp-up,” Cole said via e-mail Jan. 13.

In addition, release of the division’s Earth Venture 2 solicitation — an announcement of opportunity previously slated for release this spring that calls for competitively selected, moderately priced scientist-led missions — will be delayed until later in the year with selections anticipated in early 2012, Cole said.

NASA’s new Office of the Chief Technologist, meanwhile, has already issued two solicitations this year, including a call for space technology research fellowship proposals and an announcement of opportunity for flight payloads. A third solicitation, for flight and integration services, is expected to be released in March with responses due in May or June, according to NASA spokesman David Steitz.

“It’s our hope to announce the remaining Space Technology solicitations in each of our strategic areas (Early Stage Innovation, Game Changing Technology and Crosscutting Capability Demonstrations) as soon as Congressional deliberations allow,” Steitz wrote in a Jan. 18 e-mail, adding that budget uncertainty means his office cannot predict the number of competitive solicitations it will release this year.