Modernizing the GPS Block IIR Spacecraft

Timothy Hartman, Lawrence R. Boyd, David Koster, John A. Rajan and Jeffrey Harvey

Abstract:	Since early 1993, there has been considerable interest in making enhancements to the Global Positioning System (GPS) user interface and signal structure to accommodate new features, applications and accuracy demands. Due to the longevity of the previous generation (Block II/IIA) of GPS satellites, a window of opportunity has opened to allow improvements to be made in GPS capabilities years ahead of previous timetables. This paper will review current, near term and possible future enhancements to the GPS IIR Space Vehicle (SV) and associated ground equipment. Current enhancements in the Spacecraft Processor Unit (SPU) include the addition of SV processor data collection buffers for performance analysis. Current enhancements in the Mission Data Unit (MDU) include extensive on-orbit diagnostics capability, advances in Timekeeping Subsystem (TKS) performance, improved cross-link performance, quick program upload capability and on- orbit noise environment monitoring capability. Near term modifications will allow GPS Block IIR satellites to be modernized with considerable additional mission capabilities and flexibility. Modernized IIR (IIR-M) SVs will support additional military unique (M-code) signals on L1 and L2. Other capabilities of IIR-M include enhanced navigation software, Coarse/Acquisition (C/A) code on L2, and increased power on the present C/A and P(Y) code signals. The signal power levels output by the IIR-M SVs can be redistributed on-orbit within the C/A, P(Y) and M-code signal components as needed. The GPS IIR-M navigation payload design provides the flexibility to support future GPS signal enhancements on-orbit. Finally, we will look to the future and discuss possible SV enhancements and infrastructure upgrades that our GPS IIR team is studying at this time.
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:	2115 - 2121
Cite this article:	Hartman, Timothy, Boyd, Lawrence R., Koster, David, Rajan, John A., Harvey, Jeffrey, "Modernizing the GPS Block IIR Spacecraft," 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. 2115-2121.
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