Task: Explanation
Input (English): Claude Nicollier (born 2 September 1944 in Vevey, Switzerland) is the first astronaut from Switzerland. He has flown on four Space Shuttle missions. His first spaceflight (STS-46) was in 1992, and his final spaceflight (STS-103) was in 1999. He took part in two servicing missions to the Hubble Space Telescope (called STS-61 and STS-103). During his final spaceflight he participated in a spacewalk, becoming the first European Space Agency astronaut to do so during a Space Shuttle mission (previous ESA astronauts conducted spacewalks aboard "Mir", see List of spacewalks and moonwalks 1965–1999). In 2000 he was assigned to the Astronaut Office Extravehicular Activity Branch, while maintaining a position as Lead ESA Astronaut in Houston. Nicollier retired from ESA in April 2007. Question: Which was an air force officer and an ESA astronaut, Claude Nicollier or Roberto Vittori? Answer: Roberto Vittori
Output (English):  In 2000 he was assigned to the Astronaut Office Extravehicular Activity Branch, while maintaining a position as Lead ESA Astronaut in Houston.