From 1995 to 1997, he trained as the backup crew member for the German-Russian Mir'97 mission, and afterwards received additional training in Russia to become qualified as a second board engineer for the Mir space station. In 1998, he became a member of the European Astronaut Corps.
Schlegel was a Mission Specialist on the STS-122 Space Shuttle mission. The mission was charged with the responsibility of putting the Columbus laboratory in orbit, in addition to its connection to the International Space Station.
Hans was to perform a spacewalk on the first EVA (EVA1) of STS-122, on Sunday, 10 February 2008, in preparation for attaching the Columbus laboratory to the ISS. The EVA was postponed until Monday 11 February 2008 due to an undisclosed medical issue allegedly affecting Schlegel. Stanley G. Love performed the spacewalk instead of Schlegel. However, Schlegel did perform the second EVA on Wednesday 13 February 2008. During the spacewalk, he completed the replacement of the Nitrogen Tank Assembly on the P1 truss of the International Space Station, and installed trunnion covers on the Columbus module.
