He was the pilot of the Discovery shuttle mission in April 1991 that deployed the Gamma-Ray Observatory. He commanded the flights of Discovery in April 1993 and Atlantis in November 1995, the latter being NASA's second shuttle to dock with the Russian space station Mir. He was selected as an astronaut in 1984 and left NASA in 1996 but returned in October 2003 following the loss of the space shuttle Columbia and her crew, taking a founding position in the NASA Engineering & Safety Center as a principal engineer at Langley, then as deputy director for safety in June 2005. He retired from NASA in 2008.