NASA's first black shuttle commander said Friday he is resigning as the space agency's deputy administrator after a 31-year career.
"I've had an exciting career in NASA, but it is now time to step down so that someone younger and highly motivated can have the same experience," Frederick Gregory, 64, wrote in his resignation letter to President Bush.
The former astronaut said he will remain on the job until the Senate confirms his successor. He will probably stay at the agency even a little longer in some capacity, a NASA spokesman said.
Gregory was nominated in 2002 and became the first black in the No. 2 job at NASA. Earlier this year, he filled in as acting administrator following the resignation of Sean O'Keefe and before the appointment of Michael Griffin.
"He is the best of the best, and we have been fortunate to have his steady hand at NASA's helm during the most troubled period in NASA's history," said Griffin, his boss.
Gregory's affiliation with the space agency began in 1974, as a research pilot. He was among the first class of shuttle astronauts chosen in 1978 and flew in space three times.