Kalman filter estimates of the NAVSTAR satellite clock parameters

As is now known, the NAVSTAR/Global Positioning System is being used for precise time transfer between widely separated locations on earth. A part of this service is to provide users with information regarding the clocks in the GPS satellites. This data comes from the Kalman filter estimates in the Master Control Station at Vandenberg. This paper presents the results of an analysis of the Kalman filter data and illustrates the day-to-day characteristics of the satellite clock parameters that are provided to the time transfer user community. The monitor station tracking data also has been investigated and this paper illustrates the characteristics of the data acquired at the four monitor stations located at Vandenberg, Guam, Hawaii and Alaska. The paper shows that there are systematic and random variations in the Kalman filter estimates of the clock parameters, as well as in the tracking data. The relationship between the tracking data and the Kalman filter estimated parameters is discussed in this paper.