Block IIR Integration and Impact on GPS Performance

Bruce Gibson, Robert Fetter, Glenn Tanabe

Abstract:	The GPS Block I Developmental Satellites established initial user expectations for signal performance and characteristics. Introduction of the Block II and IIA satellites adjusted those expectations with such features as dithering, anti-spoofing, changes in page intervals, better performance, and greater reliability. The introduction of the Block IIR will add many more features that will affect users in different ways. The Block IIR vehicle has many new features, most of which will be transparent, but the user can expect to see some changes. The Block IIR vehicle will have better clocks than those of past generations. These new rubidium atomic frequency standards (RAFS) are expected to achieve performance of an order of magnitude better than their IIA predecessors. Early testing has shown that the received power levels of Ll and L2 are close to those of the Block Il/IlA. The elipticity of the Block IIR signal is expected to be more than that of the Block II/IIA, which may affect the receiver signal gain.’ The Block IIR is capable of sending and receiving navigation data via the UHF antennas between on-orbit vehicles. This capability will provide the capacity for reduced age-of-data (AOD) and will provide matching AODs across the constellation through the crosslink. The Block IIRs also have full reprogrammability that will allow future enhancements. The GPS Joint Program Office (JPO) has been conducting integration testing of the Block IIR vehicle and the Block IIR simulator with the Master Control Station (MCS) software for the last 2.5 years. This early testing of the Block IIR has been done to mitigate the risk of problems on-orbit. This test program culminates with the On-Orbit Test of the Block IIR vehicle. This test is a performance and functional test of the Block IIR capabilities and is conducted prior to the satellite navigation signal being set healthy. The first part of this paper describes and provides results of the Block II and Block IIA On-Orbit Tests. These tests were performed on the first vehicle of each new generation of GPS satellites. The second part of this paper describes the GPS JPO pre-launch testing of the Block IIR vehicle and associated MCS software. Finally, this paper discusses the On-Orbit test for Block IIR satellite and provides preliminary results of L-band RF performance and navigation performance.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	691 - 696
Cite this article:	Gibson, Bruce, Fetter, Robert, Tanabe, Glenn, "Block IIR Integration and Impact on GPS Performance," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 691-696.
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