Mark Kelly, the astronaut and husband of recovering Rep. Gabrielle Giffords, announced his retirement from the Navy and NASA Tuesday saying he plans to focus on his wife's recovery and work with her to pen a memoir.

Today, I am humbled to announce that after 25 years of service to our country, I am retiring from the United States Navy and leaving NASA, effective Oct. 1, Navy Capt. Mark Kelly wrote on his Facebook page.

I know that as our space program evolves, there are those who will question NASA's future, Kelly wrote. I am not among them. There isn't a group more dedicated to its mission or more capable than the outstanding men and women of NASA.

Gabrielle is working hard every day on her mission of recovery. I want to be by her side. Stepping aside from my work in the Navy and at NASA will allow me to be with her and with my two daughters.

Kelly commanded the last and final mission of the space shuttle Endeavour, a seamless flight to the International Space Station and had previously flown to space three times.

Giffords was shot in the head in January in a mass shooting in Tucson, AZ that slain six. She was sent to a Houston rehabilitation center in January and was released last week to go through outpatient therapy.

Gabrielle is working hard every day on her mission of recovery. I want to be by her side. Stepping aside from my work in the Navy and at NASA will allow me to be with her and with my two daughters.