Hadfield is a civilian CSA astronaut, having retired as a colonel from the Canadian Armed Forces in 2003 after 25 years of military service. He was chief of robotics for the NASA Astronaut Office at the Johnson Space Center in Houston, Texas from 2003 to 2006 and was chief of International Space Station Operations from 2006 to 2008. In 2008 and 2009, he trained as a back-up to Robert Thirsk on Expedition 21. In May 2010, Hadfield served as the commander of the mission aboard the Aquarius underwater laboratory, living and working underwater for fourteen days. NASA announced in 2010 that Hadfield would become the first Canadian commander of the International Space Station, leading Expedition 35 after its launch on December 19, 2012. His craft docked with the station on December 21. He remained on the station for five months, transferring control to Pavel Vinogradov and departing on May 13, 2013.