the first non-US citizen to fly on a space shuttle and the first European Space Agency (ESA) astronaut aboard the Russian space station Mir. His shuttle flight on Columbia with Spacelab 1 (see spacelab), in November–December 1983, included 72 scientific experiments. In January 1992, Merbold was the ESA payload specialist on the International Microgravity Laboratory aboard Discovery, with 55 scientific experiments. He was a research astronaut on Mir in October–November 1994.

Merbold was selected as an astronaut by the ESA in 1977. He was appointed head of the Astronaut Office of the Deutsches Zentrum für Luft- und Raumfahrt (DLR; German Aerospace Centre) in 1987. He was subsequently involved in the development of ESA's contribution to the International Space Station.