Early In-Orbit Performance of GPS Block IIR Rubidium Clocks
EG AND G FREQUENCY PRODUCTS SALEM MA
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The first Block IIR GPS navigation satellite, placed in orbit on July 22, 1997, carried a new generation of rubidium clocks. Since then, two of these clocks have been activated, and both are performing well. This paper reports on those early results, and compares the in-orbit performance with ground acceptance test data. EGG has delivered about two-thirds of the 66 Rubidium Atomic Frequency Standards RAFS needed for the Block IIR GPS program Composite frequency and time stability plots are presented for all delivered units, and more detailed acceptance test stability data shown for the two RAFS that are operating on-board SVN43. In addition, similar life test data shown for the two units that are undergoing life testing at NRL. In-orbit stability and drift data are presented for RAFS SN 005 and 006 using all available 15-minute precise ephemerisclock data from the National Imagery and Mapping Agency NIMA. RAFS SN 006 was turned on 81397 and was used as the active clock until 92697. RAFS SN 005 was turned on 82297 and became the active clock on 92697 at the beginning of a 2-month extended navigation test. Both are showing excellent stability and early drift stabilization.
- Test Facilities, Equipment and Methods
- Navigation and Guidance
- Unmanned Spacecraft