Measurements and analysis of the frequency stability of GPS Navstar clocks

Abstract

Analysis of the frequency stability of Global Positioning System (GPS) on-orbit Navstar clocks is performed by the Naval Research Laboratory (NRL). Clock offsets for each Navstar clock are derived from smoothed pseudorange measurements collected as the Navstar space vehicle passes over the tracking station. The clock offsets are further smoothed and estimated at the time of closest approach (TCA) of the space vehicle over the tracking station. Analysis of more than 50 Navstar clocks by NRL shows that the majority of these clocks provide performance that exceeds the GPS frequency stability specification. This precision measurement technique is capable of determining one-day frequency stabilities of the Navstar GPS clocks to an accuracy of better than 1/spl times/10/sup -13/.<>