His three NASA space shuttle flights include the May 1997 docking of Atlantis with the Russian space station Mir, during which Clervoy coordinated more than 20 experiments, and the December 1999 Discovery flight to upgrade the Hubble Space Telescope, during which he made three eight-hour space walks. He went on to be the senior adviser astronaut for ESA's Automated Transfer Vehicle (ATV). He was selected as one of the second group of French astronauts in 1985, becoming an ESA astronaut in 1992.