WASHINGTON — NASA expects its search for a permanent Mars Exploration Program director to take several months, according to an agency spokesman.

The post vacated in late December by Doug McCuistion, a former Navy commander, is currently staffed in an acting capacity by James Green, the director of NASA’s Planetary Science Division.

NASA spokesman Dwayne Brown said Jan. 3 that the agency had yet to pick a full-time successor for McCuistion, who ran the agency’s $500-million-a-year robotic Mars exploration program for the past eight-and-a-half years.

“The process will take a few months or more since it’s a senior-level position,” Brown said.

McCuistion started his NASA career at Goddard Space Flight Center, Greenbelt, Md., working on the Tracking and Data Relay Satellite System. He eventually rose to director of flight programs for NASA’s Earth Science Division. He was named Mars Exploration Program director in mid-2004.

Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...