Performance of Global Positioning System Block II/IIA/IIR On-Orbit Navstar Clocks
NAVAL RESEARCH LAB WASHINGTON DC
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Analysis of the performance of all on-orbit Navstar space vehicle clocks and Global Positioning System GPS monitor station reference clocks is performed by the Naval Research Laboratory NRL, in cooperation with the GPS Master Control Station, under the sponsorship of the GPS Joint Program Office. The measurements are collected by multi-channel GPS receivers located at the Air Force and National Imagery and Mapping Agency NIMA monitor stations. The offset of each Navstar clock, computed every 15 minutes, is referenced to the Department of Defense Master Clock. The resultant Navstar clock offsets are then used to compute frequency offset, drift offset, frequency stability profiles, and frequency stability histories. The beginning-of-life, steady state, and end-of-life performance of selected cesium and rubidium atomic clocks is presented. Frequency stability results are presented using sample times that vary from 15 minutes to several days. The stability for sample times of less than one day characterizes the measurement noise, while the stability for sample times in excess of one day characterizes both the periodic effects in the on-orbit data and the long-term performance of the Navstar atomic clocks.
- Test Facilities, Equipment and Methods
- Unmanned Spacecraft