GPS IIR-M: Modernizing the Signal-in-Space

John A. Rajan and James A. Tracy

Abstract:	ITT has been instrumental in Space Segment advancements in GPS since its inception (Figure 1) and has provided GPS payload components for every GPS satellite placed on orbit to date. In the late 1990’s, it was realized that GPS, which originated as a military system, could and should provide precise passive navigation capability to civil aviation and other civilian applications. Allowing peace time civilian access to precise navigation necessitated the need for a separate Military Unique (MU) signal. Meanwhile, the GPS Block II/IIA on-orbit satellites were considerably outperforming their design life, reducing new launch needs. These unique situations presented an opportunity to modernize many of the GPS IIR satellites that had just completed production and were in storage ready for launch if a II/IIA/IIR satellite needed replenishment. The ITT/Lockheed Martin team along with GPS Joint Program Office developed an unique approach for modernization of IIR to incorporate the MU and new L2 civil capabilities. This paper describes the innovative approaches chosen by ITT to navigate the severe programmatic and technical challenges of adding substantial GPS IIR-M capability upgrades for minimal cost and risk. The paper discusses the architectural changes and the technology insertions that were made to the IIR and the results of the modeling and prototyping efforts that validated the concept prior to the actual development. Key features and benefits of modernization are highlighted and the IIR-M flight hardware architecture is presented.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	1585 - 1594
Cite this article:	Rajan, John A., Tracy, James A., "GPS IIR-M: Modernizing the Signal-in-Space," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 1585-1594.
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