An orbital analyst tracks Kosmos 1402 in 1983.

The Space Defense Center (SDC) was a space operation center of the North American Aerospace Defense Command. It was successively housed at two Colorado locations, Ent Air Force Base, followed by Cheyenne Mountain's Group III Space Defense Center[1] The 1st Aerospace Control Squadron manned the SDC at both locations, which used the Electronic Systems Division's 496L System for processing and displaying data combined from the U.S. "Air Force's Space Track and the Navy's Spasur" (NAVSPASUR).[2][3]

The photo is from a console introduced for the 427M system, the 496L inputs were only card readers and paper tape readers, the only output was from two large line printers.


The initial 496L System was at Hanscom Field's National Space Surveillance Control Center and the second was installed at Ent Air Force Base'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.[3]

The SDC's approximately $5-million Delta I computer system at Cheyenne Mountain became operational on October 28, 1966, with about 53 individual computer programs totaling 345,000 instructions.[3] The Space Defense Center mission moved from Ent Air Force Base to "adjacent to the NORAD command center" in Cheyenne Mountain on February 6, 1967.[4]

The NORAD Cheyenne Mountain Complex Improvements Program (ESD program $427M[3] contracted in 1972,[5] operational in 1979)[6] included the Space Computational Center (SCC)"[7] intended to[8] replace the Space Defense Center[2] (the 1979 Space Defense Operations Center (SPADOC)[9] was for "replacing the SDC [sic] in Cheyenne Mountain during October.")[10]

The Space Computational Center (using the 427M computer system) replaced the Space Defense Center (which used the 496L computer system) and the SDC was closed.


  1. ^ 9th Aerospace Defense Division (abstract) (Report). Ent Air Force Base. 1966. Retrieved 2012-09-02.
  2. ^ a b Conoley, Lt. Col. Ellis K. (May 1990). Cheyenne Mountain System Acquisitions: Problems and Principles (Report). Air War College. Retrieved 2012-08-06. The Space Computational Center (SCC) would replace the 496L system."
  3. ^ a b c d Del Papa, Dr. E. Michael; Warner, Mary P. (October 1987). A Historical Chronology of the Electronic Systems Division 1947-1986 (PDF) (Report). Retrieved 2012-07-19. 1854…so-called Semi-Automatic Direction Center System, later known as…Semi-Automatic Ground Environment System, in essence, the Lincoln Transition System. … 1966…NORAD…Combat Operations Center…The center, now [1987] known as the Cheyenne Mountain Complex, integrated several distinct into a single workable unit … the Space Defense Center combining the Air Force's Space Track and the Navy's Spasur.
  4. ^ 1961-1969 Historical reports[which?] (Report). located at "Air Force Historical Research Agency, Maxwell AFB AL, AFHRA Microfilm reel KO363": 1st Aerospace Surveillance and Control Squadron.
  5. ^
  6. ^ "Cheyenne Mountain Upgrade (CMU)". FY97 DOT&E Annual Report (webpage transcription) (Report). Retrieved 2012-09-09. CMU also upgrades and provides new capability to survivable communication and warning elements at the National Military Command Center (NMCC), United States Strategic Command (USSTRATCOM), and other forward user locations. CMU additionally provides at Offutt, AFB an austere backup to Cheyenne Mountain ballistic missile warning.
  7. ^ NORAD's Missile Warning System: What Went Wrong? (PDF) (Report). U.S. Government Accountability Office. May 15, 1981. Retrieved 2012-08-06.
  8. ^ "The Worldwide Command and Control System — Evolution and Effectiveness" (PDF). Archived from the original (PDF) on February 24, 2013. Retrieved October 2, 2012.
  9. ^ "Cheyenne Mountain Operations Center (CMOC)" ( mirror webpage of former "Official Site"). Retrieved 2012-08-09.
  10. ^ [full citation needed]From satellite tracking to space situational awareness: the USAF and space surveillance, 1957-2007. Retrieved 2012-09-23.