US lawmaker Gabrielle Giffords, who was shot in the head earlier this year, honored her NASA astronaut husband Mark Kelly Thursday, at his White House naval retirement ceremony.

Captain Kelly, who commanded one of the final space shuttle missions months after his wife was assaulted by a lone gunman in Arizona, is retiring after 5,000 airborne hours as a navy pilot and four trips into orbit.

In a poignant moment of the ceremony, Giffords, who underwent life-saving brain surgery, pinned a Distinguished Flying Cross medal, earned on the shuttle Endeavour flight in May, on her husband's uniform.

Vice President Joe Biden, who presided at the ceremony in the Eisenhower Executive Office Building in the White House complex, hailed the courage of both Giffords and Kelly.

"As vice president I get to work with an awful lot of people who devote their lives day to day to public service," Biden said.

"But it's not every day you encounter examples of sheer, sheer courage, selflessness and dedication, like you see in this couple," he said.

Speaking directly to Giffords, who was making a rare journey to Washington as she recuperates, Biden said: "I don't use the word loosely. You are an inspiration. You've been inspirational."

Kelly also paid tribute to his wife's resilience since her injury.

"Gabby, you remind me every day to deny the acceptance of failure," Kelly said. "I look forward to the next phase of our life together and watching all of your future achievements."

Giffords last touched hearts in Washington after she returned to vote in the House of Representatives on a key austerity bill in August, seven months after she was shot.

A gunman shot Giffords in the head on January 8 as she met constituents at a public forum at a grocery store in Tucson, Arizona. She has needed major rehabilitation to regain movement on the right side of her body.

Six people were killed in the rampage, including a federal judge and a nine-year-old girl.