Space shuttle commander Mark Kelly to retire from Nasa

Mark Kelly, the US astronaut who commanded the final flight by the shuttle Endeavour, announced he is retiring to spend more time with his lawmaker wife as she recovers from a gunshot wound to the head.

The pair will work together on a memoir to be published by a division of Simon and Schuster, Scribner, a company spokesman said.

“As life takes unexpected turns we frequently come to a crossroads. I am at this point today. Gabrielle is working hard every day on her mission of recovery. I want to be by her side,” Mr Kelly said on his Facebook page.

Mr Kelly, 47, took on a high-profile role in the US space agency in the aftermath of the January shooting, which gravely wounded his wife Gabrielle Giffords at a political meeting in Arizona.

His painstaking decision to command Endeavour’s final flight – the second to last mission by a US space shuttle before the programme ends later this year – came as Ms Giffords was busy with a gruelling rehabilitation programme, and was supported by his family and many in the American public.

“Gabby and I are forever grateful for the heartfelt support we’ve received over these many months. We are looking forward to sharing our story,” Mr Kelly said in a statement issued by Scribner.

Last week Ms Giffords was discharged from hospital, five months after she was shot in the head at point-blank range in an attack that shocked the nation.

She has moved into her husband’s home in League City, Texas and will continue outpatient therapy, her office said.

Six people, including a federal judge and a nine-year-old girl, were killed and 12 others wounded in the January 8 shooting spree.

In March, the alleged shooter, Jared Loughner, was declared mentally unfit to stand trial. Experts found the 22-year-old to be schizophrenic and unable to help in his own defence or understand court proceedings.

Photos of a smiling Ms Giffords – who is battling to regain movement on the right side of her body after a bullet tore through the left side of her brain – were posted on her Facebook page earlier this month.

Her aides have praised her determination but acknowledged she faces a long process of rehabilitation and has difficulty expressing complex thoughts. It remains unknown if she will return to her job as a member of the US Congress.

Scribner said the memoir “will recount their courtship, Ms Giffords’ rise in US politics, and the tragic January 8 shooting in Arizona”.

“The book will also tell the story of her recovery process and will trace Mark Kelly’s career from decorated Desert Storm combat pilot to his recent mission as the commander of space shuttle Endeavour’s final flight.”