Space Defense Center

The Space Defense Center (SDC) was a Cold War operation center at 2 Colorado locations: Ent Air Force Base followed by Cheyenne Mountain's Group III Space Defense Center The  1st Aero Squadron manned the SDC at both locations which used the Electronic System Division's 496L System for processing and displaying data combined from the US "Air Force's Space Track and the Navy's Spasur" (NAVSPASUR).

History
The initial 496L System was at Hanscom Field's National Space Surveillance Control Center and the 2nd was installed at Ent AFB's Space Defense Center. The Ent SDC was one of several facilities providing data to the Cheyenne Mountain Combat Operation Center when the nuclear bunker achieved full operational capability on July 1, 1966.

The SDC's ~$5 million Delta I computer system at Cheyenne Mountain became operational on October 28, 1966, with ~53 individual computer programs totalling 345,000 instructions. The Space Defense Center mission moved from Ent to "adjacent to the NORAD command center" in Cheyenne Mountain on February 6, 1967.

The NORAD Cheyenne Mountain Complex Improvements Program (ESD program 427M contracted in 1972, operational in 1979) included the Space Computational Center (SCC)" intended to replace the Space Defense Center (the 1979 Space Defense Operations Center (SPADOC) was for "replacing the SDC [sic] in Cheyenne Mountain during October.")