PARIS — A former astronaut who was considered last year for the post of NASA deputy administrator will retire from her current position as director of the agency’s Glenn Research Center at the end of September.

NASA announced Sept. 10 that Janet Kavandi will step down as director of Glenn and retire after nearly a quarter-century at the agency at the end of the month. Kavandi has been director of the Cleveland-based center since March 2016.

In the statement, Kavandi didn’t disclose why she was leaving the agency at this time. “It was a difficult decision to call my NASA career to an end, especially at a time when the agency is preparing to send the first woman and next man to the moon,” she said. “I will be closely following the progress as I transition to the next phase of life, personally and professionally.”

Kavandi joined NASA in December 1994 when she was selected to the NASA astronaut corps. She flew on three shuttle flights from 1998 to 2001 and later served as director of flight crew operations at the Johnson Space Center. She went to Glenn in February 2015 as deputy director.

In June 2018 Kavandi emerged as a candidate to be deputy administrator of the agency. NASA Administrator Jim Bridenstine took the unusual step of endorsing her for the post, saying her experience and technical background — she has a Ph.D. in analytical chemistry from the University of Washington — made her “kind of person at this juncture, given how important everything is right now, that we need as our deputy.”

The White House, though, nominated Jim Morhard, a veteran Senate staffer who had most recently been the deputy sergeant-at-arms for the Senate, for the position of deputy administrator in July 2018. The Senate confirmed Morhard by voice vote in October.

Kavandi’s departure took some in the space industry by surprise, as there had been no hints she was planning to leave the agency. She hosted Bridenstine and two members of Congress at Glenn Aug. 21 to show off what the center was contributing to the Artemis program, and some speculated she might be a candidate to become the next associate administrator for human exploration and operations, succeeding Bill Gerstenmaier, who was reassigned in July.

NASA did not announce who would succeed Kavandi as Glenn director, saying only that “Glenn leadership changes following Kavandi’s retirement will be announced at a later date.”

Kavandi is the second NASA center director to retire this month. David Bowles is retiring at the end of September as director of the Langley Research Center after nearly four decades at the agency. NASA announced Sept. 9 that Clayton Turner, the current deputy director of Langley, will succeed Bowles on Sept. 30.