(; 17 October 1926 – 5 October 1993) was an American astronomer, space scientist, NASA astronaut, and professor at Northwestern University.
He was stationed at several observatories around the world, including McCormick Observatory, Lamont-Hussey Observatory (South Africa), Mount Wilson Observatory, Smithsonian Astrophysical Observatory and Mount Stromlo Observatory (Australia).
He was a member of the astronaut support crew for Apollo 15 and Skylab 2, 3, and 4.
As a mission specialist on the Spacelab-2 mission (STS-51-F), he flew on Space Shuttle Challenger in July/August 1985.
He was awarded the NASA Exceptional Scientific Achievement Medal in 1974.
He died in 1993, during a Mount Everest expedition while testing equipment for NASA.