US astronaut. His four space shuttle flights include the Discovery launch in September 1988, the first shuttle mission after the Challenger tragedy of 1986. In January 1992, he flew with the Discovery mission that conducted 55 experiments in the Microgravity Science Laboratory. In October 1992 he left NASA to begin his medical studies at Baylor College of Medicine. He was selected as an astronaut in 1980.
Subjects: Astronomy and Astrophysics.