Charles Donald "Sam" Gemar is an American former astronaut with NASA and a lieutenant colonel in the United States Army. Gemar has flown on three Space Shuttle missions. Gemar has completed 385 orbits of the Earth and over 581 hours in space. He has also served in different positions in NASA, including as a CAPCOM for Shuttle missions. Gemar was the first astronaut to be born in the state of South Dakota.

STS-38 was a Space Shuttle mission by NASA using the Space Shuttle Atlantis. It was the 37th shuttle mission, and carried a classified payload for the U.S. Department of Defense (DoD). It was the seventh flight for Atlantis and the seventh flight dedicated to the Department of Defense. The mission was a 4-day mission that traveled 3,291,199 km (2,045,056 mi) and completed 79 revolutions. Atlantis landed at Kennedy Space Center's Shuttle Landing Facility's runway 33. The launch was originally scheduled for July 1990, but was rescheduled due to a hydrogen leak found on Space Shuttle Columbia during the STS-35 countdown. During a rollback to the Orbiter Processing Facility Atlantis was damaged during a hail storm. The eventual launch date of November 15, 1990, was set due to a payload problem. The launch window was between 18:30 and 22:30 EST. The launch occurred at 18:48:13 EST.