Studied mathematics and physics and graduated from Nuclear Physics Accelerator Institute (K.V.I) in Groningen, 1973; Ph.D. in physics and mathematics from the University of Groningen, 1978; research scientist at K.V.I.; successfully completed MSP training as a member of NASA astronaut class IX, 1981; alternate PSP STS-9, 1983; nominated by ESA as the second candidate PSP for IML-1, 1985; stationed at ESA's research and technology centre, ESTEC, in Noordwijk, the Netherlands, where he supported human spaceflights activities, 1986; became later Head of ESA's Education and Outreach Office in Noordwijk; during this time he also held a part-time professorship in Aerospace at the Delft University of Technology (TU Delft); member of the prime crew for the Spacelab D-2 mission, but the new safety rules after the Challenger accident (a maximum of seven crewmembers) prevented him from flying, 1988; nominated by the Investigator Working Group for IML-2 as a PSP and unanimously supported by the ESA member states in a letter to NASA for a second (European) PSP on that mission, 1992; one of six ESA candidates for the EuroMir flights, but was rejected because of a minor medical problem, 1993; retired from active duty, 1994; continues working as a part-time professor at TU Delft and at the University of Groningen; recovered of a severe heart attack, 2005.