Transition of GPS Fleet to Upgraded Control System

Los Angeles Air Force Base, El Segundo, Calif. — The Air Force is completing final preparation for transitioning the Global Positioning System ground segment to the new Architecture Evolution Plan in September. AEP was developed by the Space and Missile Systems Center’s GPS Wing, under contract with Boeing, to replace the legacy 1970s-era mainframe computer at the 50th Space Wing, Schriever AFB, Colo.

AEP is designed to improve operations, increase efficiency, and provide a foundation for new capabilities as they become available. When installed, the system will enable upgrades to control the soon-to-be-launched GPS Block IIF satellites. It will provide the foundation for a new security architecture supporting troops fighting the global war on terrorism.

The Air Force team, along with contractors from Boeing, Lockheed Martin and The Aerospace Corporation, have been preparing for transition to the new control segment since March 2006. The team has focused on ensuring GPS service will not be interrupted during the changeover from the legacy system to AEP.

The transition will take place over a period of four to six days and will transfer control to AEP one satellite at a time. The transition has been successfully rehearsed three times and is completely reversible if any problems are encountered. Users of the system should not notice the transition.

GPS is the world’s premier space-based positioning, navigation, and timing system supporting land, sea, and airborne navigation for military and civilian users around the world. The system is comprised of up to 30 satellites on orbit which broadcast a navigation message to users worldwide.

The ground segment provides command and control of the satellites and generates the navigation message for satellites to broadcast to users so they can determine their position on the earth. The new control segment is a critical part of an overall modernization plan to improve operations, sustainment, and overall service.

The Space and Missile Systems Center, located at Los Angeles Air Force Base, Calif., is the U.S. Air Force’s center of acquisition excellence for acquiring and developing military space systems including six wings and three groups responsible for GPS, military satellite communications, defense meteorological satellites, space launch and range systems, satellite control network, space based infrared systems, intercontinental ballistic missile systems, and space situational awareness capabilities. SMC manages more than $60 billion in contracts, executes annual budgets of $10 billion and employs more than 6,800 people worldwide.

The 50th Space Wing at Schriever AFB, Colo. through the 2nd Space Operations Squadron, performs the satellite command control mission for GPS and the new AEP. GPS is the world’s largest military satellite constellation, providing highly accurate, 24- hour, all-weather, positioning, navigation, and timing data to military and civilian users worldwide. 2nd SOPS operates and maintains the Master Control Station at Schriever AFB and a dedicated network of worldwide monitor stations and ground antennas to control and support this constellation.

The 50th Space Wing operates satellite operations centers, remote tracking stations, and other command and control facilities around the world. These facilities monitor satellites during launch, put the satellites in their proper orbits following launch, monitor and control the satellites while they are in orbit, fix satellite anomalies when they occur, and dispose of satellites when they reach the end of their useful life. In addition to GPS, the wing operates several satellite systems including the Defense Satellite Communications System and Milstar. The wing also operates the Air Force Satellite Control Network which operates seven worldwide remote tracking stations.

For GPS AEP acquisition and development questions, please e-mail the Los Angeles AFB Public Affairs Office at or call (310) 653-2369/2371.

For GPS AEP operational questions, please contact the Schriever AFB Public Affairs Office at (719) 567-5448.