Modernization of the GPS Satellite Constellation

Gary Rafferty, Rob Lewis and Tony Occhi

Abstract:	This paper introduces Headquarters Air Force Space Command, Global Positioning System (GPS) Requirements Division (HQ AFSPC/DRN), defines the requirements process, and explains how those requirements are materialized and made available to military and civil communities. HQ AFSPC/DRN, located at Peterson AFB, CO, is the agency responsible for collecting military and civil GPS system requirements. These requirements are driven by the March 1996, Presidential Decision Directive (PDD) "U.S. Global Positioning System Policy (National Science and Technology Council [NSTC]-6)." This policy states that the Global Positioning System (GPS) is a dual use-- military and civil--space based positioning, navigation, and timing (PNT) system operated by the Department of Defense (DoD). As a result, HQ AFSPC/DRN examined the Federal Radionavigation Plan (FRP), a DoD/Department of Transportation (DOT) publication for civil GPS PNT requirements, and the AFSPC Mission Need Statement (MNS) 003-92 for military navigation and timing related needs. The GPS system is composed of the Control, Space, and User Segments. HQ AFSPC/DRN is responsible for the Control and Space Segment requirements. The requirements defined in the GPS Operational Requirements Document (ORD), approved by the Joint Requirements Oversight Council and AF Chief of Staff, specify military and civil requirements for the GPS Space and Control segments. The GPS Joint Program Office (JPO), located at the Los Angeles Air Force Base, then takes the GPS ORD and presents a technical solution (a system or capability) for operation by AFSPC/DO. To meet the system-level accuracy improvements in the GPS ORD, the GPS JPO is concentrating on improving the Control Segment through he Architecture Evolution Plan (AEP) and Accuracy mprovement Initiative (AII) and improving the Space Segment capabilities through a phased approach spread over several generations of new spacecraft. The GPS III system will complete this round of GPS System modernization.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	2562 - 2564
Cite this article:	Rafferty, Gary, Lewis, Rob, Occhi, Tony, "Modernization of the GPS Satellite Constellation," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 2562-2564.
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