Mark Kelly, husband of Rep. Giffords, retires from Navy

(CNN) - Mark Kelly, the astronaut and husband of U.S. Rep. Gabrielle Giffords, formally retired from the Navy on Saturday.

Kelly, 47, is a former Navy combat and test pilot who went on to command Space Shuttle flights in 2008 and again in May, several months after his wife, U.S. Rep. Gabrielle Giffords, was wounded in a shooting at a constituent event in Tucson, Arizona. He also flew as part of Shuttle crews in 2001 and 2006.

He announced his retirement in June and it became effective on Saturday.

In a posting on his Facebook page at the time, he said he wanted to devote more time to helping Giffords recover from her injuries, and also to spend more time with his daughters from a previous marriage.

"This was not an easy decision. Public service has been more than a job for me and for my family," Kelly wrote on his Facebook page at the time.

Kelly joined the Navy in 1987 after graduating from the U.S. Merchant Marine Academy in 1986.

Kelly and Giffords have a book coming out on November 15.