PERFORMANCE OF GLOBAL POSITIONING SYSTEM BLOCK II/IIA/IIR ON-ORBIT NAVSTAR CLOCKS

摘要

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 (JPO). The measurements used in the analysis 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 is computed with respect 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 performance of selected cesium and rubidium atomic clocks will be presented. Frequency stability results are calculated using sample times that vary from 15 minutes to several days. The operational Navstar timing signals will be ranked (according to frequency stability) for sample times of 6 hours and 1 day. in addition, the Block IIR clocks will be compared to results from an ongoing NRL laboratory life-test on two flight-qualified Block IIR rubidium atomic frequency standards. Observed clock behavior and anomalies will be discussed.