Mark Kelly, the husband of Rep. Gabrielle Giffords, D-AZ, said Tuesday that he will be retiring from NASA after 25 years of working with the space agency.

In a note posted to his Facebook account, Kelly said the main reason for his retirement was largely due to his desire to help her wife recover from a gunshot to wound to the head she suffered at an Arizona shopping mall early this year by an attacker alleged to have killed six others around her, including a 9-year-old girl.

Gabrielle is working hard every day on her mission of recovery. I want to be by her side, he said.

Stepping aside from my work in the Navy and at NASA will allow me to be with her and with my two daughters.

Giffords, 41, was recently released from a Houston hospital and is set to receive outpatient therapy.

Kelly's announcement came a few weeks after he made his last journey to the International Space Station with the Endeavour space shuttle.

Kelly's announcement is not unexpected since NASA is retiring its space shuttle fleet in one month, and it will be years before the United States has another spacecraft for astronauts to fly in.

The final shuttle launch is scheduled for July when Atlantis is set to take off. After that, NASA will depend on Russian spacecraft to get astronauts into space.

I know that as our space program evolves, there are those who will question NASA's future. I am not among them, said Kelly.

The Arizona Democrat and her husband are working on a memoir currently. The book will reportedly be an intimate look at their careers and courtship. The book will be published by Scribner and a publishing date has not yet been decided.

Giffords is recovering and learning to talk and walk again. She is living in Kelly's home in League City, Texas, near Houston.

The couple first met in China in 2003 during a young leaders' forum and were married in November of 2007.