Extended Scheme of Satellite Clock Time Offset Prediction Using the Unequal Accuracy Data

A. V. Saltsberg, K. G. Shupen

Transactions of IAA RAS, issue 52, 51–56 (2020)

DOI: 10.32876/ApplAstron.52.51-56

Keywords: GNSS, onboard frequency standards, time scales, Kalman filter, satellite clock time offset, prediction

Abstract

The primary goal of the time/frequency support of GNSS is calculating and predicting the satellite clock time offset (SCTO) for an onboard time scale of a space vehicle. The accuracy of predicting SCTO depends crucially on the following: the term of the prediction and the selection of observation interval, reliable calculation of onboard frequency standard parameters and the mathematical model selected for the time offset prediction. These factors should be considered for optimizing the strategy of SCTO prediction and, as a result, for increasing the accuracy of GNSS time/frequency support. A sequence of comparing and analyzing data on the space vehicle SCTO from various sources is presented, a technique for eliminating differences in system time scales, including that through the transmitted GNSS segment, is considered. An extended prediction scheme using unequal data from different sources is proposed, the key elements and limitations of the scheme are determined. The results of using this approach to improve the medium-term prediction of SCTO are presented. The extended prediction scheme is based on the use of all accessible information on the current values of SCTO provided by different sources carrying out GNSS measurements processing: GNSS data, the information from functional additions systems, highly-precision real time systems. The scheme suggested can be considered an effective means for data deficiency problem solution.

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