A.V. Saltsberg1, K.G. Shupen2

1,2 JSC “Russian Institute of Radionavigation and Time” (Saint-Petersburg, Russia)

One of the main factors determining the achievable performance of the GLONASS system is the satellite time clock offset prediction error. The most promising way to increase the accuracy of prediction is a detailed account of the characteristics of stochastic processes underlying the time scale generation process. Each atomic frequency standard, being a complex physical device, has unique characteristics that should be taken into account when constructing a mathematical model and the prediction algorithm for satellite clock time offset, the source of which is the frequency signals of the created frequency standard.

The prospects for creating digital twins of atomic frequency standards as one of the ways to improve the global navigation satellite systems performance are considered. A scheme of a scientific-experimental complex for ground testing and onboard clock operation monitoring with the aim of collecting statistical and analytical information for creating a digital twin of each developed atomic frequency standard is presented.

Estimation of the atomic frequency standard characteristics is the main factor that determines how effectively a given source of highly stable frequency can be used for the purposes of timekeeping. Despite this, in the ground testing of atomic frequency standards samples, the predictability analysis of their time scales is not included in the test program, although its results can be effectively used to build optimal models for predicting the satellite clock time offset during operation. For this purpose, a scheme for conducting atomic frequency standard ground tests that allows using the obtained performance estimates to optimize the mathematical model and the clock offset prediction algorithm for a particular satellite clock can be recommended.

An a posteriori analysis of the onboard clock behavior shows that the structure of the currently used mathematical model does not accurately reflect the real process of the satellite clock time offset. According to existing studies, this process has periodic components due to the satellite orbit motion and other factors. To solve this problem, a qualitative model for taking into account the influence of the operating conditions on the behavior of the satellite clock time scale is presented.

The resulting simulation models can be used as sources of initial data for optimizing satellite clock time offset prediction algorithms and for improving the mathematical models that take into account the individual characteristics of a particular atomic frequency standard and also for studying the influence of operating conditions on the satellite clock performance and, consequently, to increase the GLONASS navigation accuracy.

Saltsberg A.V., Shupen K.G. Ways to optimize mathematical models of satellite clock time offset. Radiotekhnika. 2023. V. 87. № 3. P. 98−108. DOI: https://doi.org/10.18127/j00338486-202303-10 (In Russian)

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