GPS CLOCKS IN SPACE: CURRENT PERFORMANCE AND PLANS FOR THE FUTURE

摘要

The ITT Industries-developed GPS IIR satellite pay loads have been on-orbit since 1997, providing outstanding signal-in-space performance. Much of credit for this outstanding performance can be given to the GPS IIR Time Keeping System (TKS) and the GPS-IIR spacecraft bus, which keeps the payload in a mechanically and thermally stable condition. A key component of the TKS system is PerkinElmer's rubidium atomic frequency standard (RAFS). We now have a grand total of 15 years of on-orbit experience with the GPS IIR TKS and RAFS. In this paper we will present the current on-orbit performance of GPS IIR TKS and RAFS. Since GPS IIR, ITT and PerkinElmer have made significant performance enhancements to the TKS and RAFS. This paper will highlight performance of the next generation TKS with the enhanced RAFS (ERAFS) and an improved precision phase meter (PPM). The paper discusses current on-orbit performance of the GPS IIR TKS and RAFS and shows that they match expectations. The paper also discusses the modifications that comprise the ERAFS and associated performance improvement over the legacy RAFS. Finally, the paper discusses potential performance enhancements for the next generation TKS.