Kirk Shireman, NASA ISS program manager, watches the launch of the Demo-2 commercial crew mission May 30 from a firing room at the Kennedy Space Center. Credit: NASA/Joel Kowsky

WASHINGTON — Kirk Shireman, who has managed the International Space Station program for NASA for five years, will retire later this month, the agency announced June 16.

Shireman will leave the agency June 26 to take a position in the private sector, NASA said in a statement. Joel Montalbano, deputy ISS program manager, will take over as acting program manager on that date.

“Kirk has dedicated 35 years of his career advancing and improving human spaceflight, and doing it in a collaborative way,” Kathy Lueders, the associate administrator for human exploration and operations, said in the statement. “I am confident Joel’s leadership of this program will continue to expand the role of the space station as a national asset for exploration, science, and commercial use.”

Shireman joined NASA in 1985 working on the shuttle program and, in 1994, shifted to the space station program. He was deputy ISS program manager from 2006 to 2013, then served as deputy director of the Johnson Space Center before being named ISS program manager in August 2015.

“It has been the honor of a lifetime to have worked through the development of the International Space Station from a fledgling facility to a world-class laboratory,” Shireman said in the NASA statement, calling the station “the most complex human engineering achievement of all time.”

There had been no signs that Shireman was planning to retire from NASA, and many within the agency were surprised by the announcement. It came just a few days after Lueders, formerly manager of the commercial crew program, took over as associate administrator for human exploration and operations.

Montalbano has been deputy ISS program manager at NASA since 2012. He joined the agency in 1989 and previously worked as a flight director and as director of NASA’s human spaceflight activities in Russia.

Shireman has announced what specific position he will take in the private sector after leaving NASA. His predecessor as ISS program manager, Mike Suffredini, also left the agency in 2015 to work in the private sector. Suffredini is now the president and chief executive of Axiom Space, a commercial space station company.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...