Control Segment

Map showing the master control station at Schriever AFB Colorado; alternate master control station at Vandenberg AFB California; ground antennas in Cape Canaveral Florida, Ascension, Diego Garcia, and Kwajalein; AFCSN remote tracking stations in Hawaii, Vandenberg AFB, New Hampshire, Greenland, United Kingdom, Diego Garcia, and Guam; Air Force monitoring stations in Hawaii, Schriever AFB, Cape Canaveral, Ascension, Diego Garcia, and Kwajalein; and NGA monitoring stations in Alaska, Ecuador, USNO Washington, Uruguay, United Kingdom, South Africa, Bahrain, South Korea, Australia, and New Zealand

The GPS control segment consists of a global network of ground facilities that track the GPS satellites, monitor their transmissions, perform analyses, and send commands and data to the constellation.

The current Operational Control Segment (OCS) includes a master control station, an alternate master control station, 11 command and control antennas, and 16 monitoring sites. The locations of these facilities are shown in the map above. View as PDF (111 KB)

Air Force Personnel: Team Blackjack

Air Force video: 2SOPS keeps GPS flying! (2009)

Team Blackjack mission patch The GPS constellation delivers consistently high performance thanks to the dedicated efforts of its operators — the men and women of the U.S. Air Force's 2nd Space Operations Squadron (2SOPS) and the Air Force Reserve's 19th Space Operations Squadron (19SOPS) at Schriever Space Force Base, Colorado.

Together, 2SOPS and 19SOPS — nicknamed Team Blackjack — keep the GPS satellites flying on a 24/7 basis, with continuous availability and high accuracy for billions of civilian and military users.

More Information

Control Segment Elements

Monitor station receiving signals from satellite
Monitor Stations

  • Track GPS satellites as they pass overhead
  • Collect navigation signals, range/carrier measurements, and atmospheric data
  • Feed observations to the master control station
  • Utilize sophisticated GPS receivers
  • Provide global coverage via 16 sites: 6 from the Air Force plus 10 from NGA

Master Control Station

  • Provides command and control of the GPS constellation
  • Uses global monitor station data to compute the precise locations of the satellites
  • Generates navigation messages for upload to the satellites
  • Monitors satellite broadcasts and system integrity to ensure constellation health and accuracy
  • Performs satellite maintenance and anomaly resolution, including repositioning satellites to maintain optimal constellation
  • Currently uses separate systems (AEP & LADO) to control operational and non-operational satellites
  • Backed up by a fully operational alternate master control station

Satellite dish transmitting signal to satellite
Ground Antennas

  • Send commands, navigation data uploads, and processor program loads to the satellites
  • Collect telemetry
  • Communicate via S-band and perform S-band ranging to provide anomaly resolution and early orbit support
  • Consist of 4 dedicated GPS ground antennas plus 7 Air Force Satellite Control Network (AFSCN) remote tracking stations

Control Segment Modernization

Montage of satellite dish, GPS constellation around Earth, and a GPS satellite As part of the GPS modernization program, the Air Force has continuously upgraded the GPS control segment for many years. The ground upgrades are necessary to command and control the newer GPS satellites and to enhance cybersecurity.

Ongoing Upgrades

Past Upgrades

Learn more about GPS modernization

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