STS-39

STS-39 was the twelfth flight of Space Shuttle Discovery and the first unclassified Shuttle mission dedicated to Department of Defense payloads. Michael Coats, Lloyd Blaine Hammond Jr., Guion Bluford, Gregory Harbaugh, Richard Hieb, Donald McMonagle, and Charles Lacy Veach launched from Kennedy Space Center Launch Complex 39A on April 28, 1991. The crew operated Air Force Program-675, the Infrared Background Signature Survey with SPAS-II, Space Test Payload-1, radiation monitoring, CLOUDS-I, and a classified Multi-Purpose Experiment Canister. Discovery deployed and later retrieved the SPAS-II platform so instruments could observe Shuttle engine firings, gas releases, and orbital-environment signatures from a distance. The mission landed at Kennedy Space Center on May 6 after 134 orbits and more than eight days in space.