NASA’s topline budget for fiscal 2013 will be reduced by $726.7 million as compared to its budget request if sequestration takes effect March 1, with a significant portion of that cut being absorbed by the agency’s efforts to nurture commercial systems for transporting crew and cargo to low Earth orbit.

“Sequestration would reduce Commercial Space Flight funding by $441.6 million below the FY 2013 budget request,” writes Administrator Charles Bolden in a letter to Senate Appropriations Committee Chair Barbara Mikulski (D-Md.).

As a result, NASA would not be able to make fourth-quarter milestone payments to the industry teams working on the Commercial Crew Integrated Capability (CCiCap) program, including for SpaceX’s Inflight Abort Test Review, Boeing’s Orbital Maneuvering and Attitude Control Engine Development Test, and the Sierra Nevada Corp.’s Integrated System Safety Analysis Review #2, according to Bolden.

“Overall availability of commercial crew transportation services would be significantly delayed, thereby extending our reliance on foreign providers for crew transportation to the International Space Station,” he says.

The overall Exploration budget would see a reduction of $332.2 million as compared to its $3.9 billion fiscal 2013 request.

The agency’s Space Technology budget would see a steep reduction of $149.4 million, as compared to its $699 million fiscal 2013 request. As a result, NASA says it would have to consider options including canceling technology development projects; scrapping several flight demonstrations; eliminating or scaling back annual solicitations for Space Technology Research Grants, NASA Innovative Advanced Concepts and the Small Spacecraft Technology Program; reducing the number of Flight Opportunity program flights and payloads in fiscal 2013 and beyond; and eliminating the Centennial Challenges prize program.

The agency’s science budget would take a relatively modest hit of $51.1 million, as compared to its $4.9 billion fiscal 2013 request. This would result in reducing funding for new Explorer and Earth Venture class missions by 10-15%, and reducing competed research and analysis funding by 2%.

Aeronautics would see a reduction of $7.3 million, as compared to its $551.5 million fiscal 2013 request. And the agency’s construction programs would see a reduction of $251.7 million, as compared to their $619.2 million fiscal 2013 request.

NASA has been operating under a continuing resolution for fiscal 2013 that essentially sets funding at fiscal 2012 levels. Since the agency’s fiscal 2012 budget was larger than its fiscal 2013 request, sequestration results in an $894.1 million cut to its topline when compared to the continuing resolution.