In April 1990, Sullivan served on the crew of STS-31, which launched from Kennedy Space Center, Florida, on April 24, 1990. During this five-day mission, crew members aboard the Space Shuttle Discovery deployed the Hubble Space Telescope, and conducted a variety of middeck experiments involving the study of protein crystal growth, polymer membrane processing, and the effects of weightlessness and magnetic fields on an ion arc. They also operated a variety of cameras, including the IMAX cargo bay camera, for earth observations from their record setting altitude of 380 miles. Following 76 orbits of the earth in 121 hours, STS-31 Discovery landed at Edwards Air Force Base, California, on April 29, 1990. In 1985, she became an Adjunct Professor of Geology at Rice University.