Two NASA officials to step down

Two top NASA officials, including the man in charge of developing new spacecraft for future missions to the moon and Mars, plan to leave the space agency, a spokeswoman said Thursday.

Former astronaut Scott “Doc” Horowitz, who heads NASA’s exploration systems mission directorate, will leave by October. Associate administrator Rex Geveden will leave at the end of this month.

The timing of both decisions was coincidental, and neither was asked to leave by NASA Administrator Michael Griffin, spokeswoman Beth Dickey said.

Horowitz leaves at a crucial time for the development of next-generation spacecraft as NASA finishes signing development contracts and works around a funding squeeze that forced the agency to push back the first manned flight of the new Orion spacecraft to 2015. No successor has been named.

Horowitz said he wanted to move back to Utah and spend more time with his family. He expects to be an aerospace consultant, Dickey said.

Horowitz was a pilot and commander on four shuttle missions before leaving NASA in 2004 to become director of exploration and space for ATK in Utah, which produces the space shuttle’s solid rocket motors.

He returned to NASA in 2005 to head the explorations directorate, which is devoted to developing both the Orion and the Ares rockets that NASA hopes will deliver astronauts and cargo to the moon no later than 2020.

Geveden will be president of Teledyne Brown Engineering Inc. in Huntsville, Ala. He joined NASA in 1990 and became associate administrator in 2005. Christopher Scolese, NASA’s chief engineer, will succeed him.