WASHINGTON — U.S. Sen. Barbara Mikulski (D-Md.), who chairs the Senate Appropriations commerce, justice, science subcommittee that oversees NASA spending, said astronaut safety, mission destination and work force transition would be among a half-dozen core principles she will use to draft the agency’s 2011 appropriations bill.

In a Feb. 16 letter to Sen. Bill Nelson (D-Fla.), chairman of the Senate Commerce science and space subcommittee, Mikulski said she would be looking to the authorizing committee’s close examination of President Barack Obama’s $19 billion spending proposal for NASA in 2011, which would scrap the agency’s Moon-bound Constellation program in favor of fostering development of a commercial crew transportation service to low Earth orbit.

“The Administration has proposed a new direction for America’s space program and I believe it is now more important than ever for the Commerce and Appropriations Committees to work in consultation as we consider the Administration’s proposals,” she wrote, adding that she thought it might be helpful to share with Nelson the “principles that I will rely on when drafting the fiscal year 2011 funding bill for NASA.”

Chief among those principles is astronaut safety, which Mikulski said must be assured by the system NASA chooses for transporting astronauts to low Earth orbit.

“This means whichever transportation system is chosen, it must protect astronauts during launch, mission execution and re-entry, including during long duration space flight,” she wrote.

Mikulski also stressed the importance of having a clear destination for NASA’s human spaceflight program.

“Since NASA’s creation, it has been a mission driven agency, and I believe having a clear direction and destination has contributed to NASA’s many successes,” she wrote. “NASA must continue to have a mission driven focus. To the maximum extent practicable, we should engage our international partners in formulating common destinations for human and robotic missions.”

Mikulski said she believes the space program must be balanced, and that science should continue to be its driving purpose. “This means human space flight that includes a safe, reliable vehicle, Earth and space scientific exploration, and aeronautics research and technology development,” she wrote. “These objectives must be appropriately balanced in any future authorization or appropriations legislation.”

NASA should also maximize its current and future scientific assets in “low earth orbit and beyond.”

“This includes the extension of the International Space Station (ISS), which should be re-supplied with cargo by commercial vehicles,” she wrote. “As we witnessed with the Hubble Space Telescope, a human space flight program dedicated to the advancement of science yields truly extraordinary results for the United States and the entire world.”

Nelson, who has criticized the president’s plan to abandon Constellation and the Ares family of rockets being developed to support it, shares Mikulski’s desire to sustain the nation’s status as a global tech leader through human spaceflight missions.

“Between them there is a common interest in making sure the U.S. maintains its leadership in science and technology via manned space exploration,” Dan McLaughlin, Nelson’s press secretary, told Space News Feb. 19.

Nelson is also concerned with NASA’s plan to transition the space shuttle work force once the agency’s aging fleet of orbiters retires later this year. His state stands to lose nearly 7,000 jobs as a result of shuttle retirement.

In her letter, Mikulski said plans to retire the space shuttle should proceed after assembly of the international space station is complete this year, but added that any future direction must include a plan to maintain critical skills and incorporate lessons learned from our previous efforts to replace the shuttle, “and to soften any job dislocation impacts.”

When administration officials appear before her subcommittee to defend Obama’s proposal, Mikulski said, she will question where NASA is planning to go, how it will get there, and what it will take. She also wants to know if Obama’s intention is to “scrap everything and start over,” according to the letter. If so, Mikulski expects a plan to mitigate job dislocation and answers as to how the shift in direction will protect investments in Earth and space science and aeronautics proposed in the 2011 budget request and in the years ahead.

Mikulski intends to hold her subcommittee’s first NASA hearing on the 2011 budget March 25, according to an aide to the senator.

Nelson’s subcommittee will hold its first NASA hearing on the proposed budget Feb. 24.