German physicist and retired ESA astronaut who flew on one space mission, STS-99.
He received his PhD in environmental physics from the University of Heidelberg in 1985.
In July 2013 he became the head of the ESA's Human Spaceflight and Operations Strategic Planning and Outreach office.
He married and had four children.
He trained as back-up for Andre Kuipers on the Soyuz TMA-4 mission.