NASA Administrator Mike Griffin is planning to leave office on Jan. 20, and a short list of potential replacements is starting to emerge as the incoming Obama administration moves toward Inauguration Day.

Griffin, a veteran rocket scientist who always has said he serves at the pleasure of the president, does not expect to be offered an opportunity to stay on after President-elect Barack Obama takes office.

He and all other political appointees from the Bush administration have submitted their letters of resignation as a matter of course. All are effective Jan. 20, a Tuesday. Monday, Jan. 19, is a federal holiday, so that means the preceding Friday would be Griffin's last day in his ninth-floor office at NASA headquarters in Washington, D.C.

Friends and family are campaigning and petitioning for Obama to keep Griffin on board, but all indications are that a new NASA administrator will be nominated along with a new NASA deputy administrator sooner rather than later.

The Government Accountability Office rated the impending retirement of NASA's shuttle orbiter fleet as one of the top 13 issues the new president will have to deal with in short order. The administration is expected to nominate new NASA leadership before making any significant decisions regarding U.S. space policy and the future of the human spaceflight program.

According to congressional sources, a former astronaut who would be the first black NASA administrator leads the list of potential candidates.

Charlie Bolden flew four times on the space shuttle, including the mission to deploy NASA's flagship Hubble Space Telescope and the historic first joint U.S.-Russian shuttle mission.

He also flew on a 1986 mission with then-congressman Bill Nelson, who now is the senior U.S. senator from Florida.

Nelson likely will be a key figure in the selection process. He runs the Senate committee that oversees NASA and has been advising Obama on the future of the nation's space agency.

Nelson declined comment on the possibility of Bolden heading NASA. But his spokesman, Dan McLaughlin, said, "The senator views him as a top-notch individual."

Bolden told FLORIDA TODAY he has not been contacted by representatives of the incoming Obama administration or its transition team.

He added, though, that he would be open to having a conversation about the future of NASA.

Other potential candidates might include:

• Sally Ride, who became the first American woman to fly in space in 1983. Ride, who served on the commissions that investigated both the Challenger and Columbia accidents, wrote an editorial in support of Obama during the presidential election.

• Alan Stern. The principal investigator of a mission to Pluto, Stern served a short term as associate administrator for the Science Mission Directorate at NASA headquarters. After he left, Stern criticized NASA for ongoing cost overruns in space and planetary science missions.

• Wesley Huntress. A former NASA space science chief, Huntress played a key role in the deployment of a series of vitally important planetary science missions after the 1986 Challenger accident, including the Magellan Venus Radar Mapper, the Hubble Space Telescope and the Galileo Jupiter probe.

• Scott Hubbard. Known for turning around NASA's Mars program after back-to-back failures in the late 1990s, Hubbard was a key member of the Columbia Accident Investigation Board. He went on to serve as a director of NASA's Ames Research Center before leaving the agency for academia.

• Video - Sally Ride: America's 1st Female Astronaut
• Video - NASA's Constellation Journey Begins: Part 1, Part 2
• End in Sight: Final Space Shuttle Missions Slated

Published under license from FLORIDA TODAY. Copyright © 2009 FLORIDA TODAY. No portion of this material may be reproduced in any way without the written consent of FLORIDA TODAY.