Kelly wrote, "Words cannot convey my deep gratitude for the opportunities I have been given to serve our great nation. From the day I entered the United States Merchant Marine Academy in the summer of 1982 to the moment I landed the Space Shuttle Endeavour three weeks ago, it has been my privilege to advance the ideals that define the United States of America."
During his 15 year career at NASA, Kelly has traveled to the International Space Station four times aboard space shuttles Endeavour and Discovery.
In his posting, he adds that his brother, Scott Kelly, continues to serve in NASA and the Navy. Kelly says he plans to spend more time with his two daughters, and his wife, Representative Gabrielle Giffords, as she continues her recovery from the shooting in Tucson, Arizona, last January.
Kelly and Giffords have also announced they have a deal for a joint memoir that will include the tragic shooting. The book is currently untitled and will be released by Scribner at a date to be determined. Kelly and Giffords will collaborate with Jeffrey Zaslow, best known for his work on Randy Pausch's million-selling "The Last Lecture."