K.G. Shupen1, V.F. Braginets2, V.M. Meshcheryakov3

1-3 JSC “Scientific and Production Corporation “Precision Instrument Systems” Branch “PNBO” (Korolev, Russia)

1 k.shupen@mail.ru; 2 braginets@spnav.ru; 3 messer58@mail.ru

Problem Statement. One of the main tasks of the GLONASS system is to transmit precise time using signals from navigation satellites, ensuring that the user's time scale is linked to the national coordinated time scale of Russia (UTC(SU)). One of the main limiting factors in transmitting precise time, in addition to receiving equipment calibration, is the accuracy of the ephemeris and clock time offsets in the navigation message. This limitation can be overcome by using a functional complement to the GLONASS system—a Global System for High-Precision Determination of Ephemeris and Clock Information (SVO EVI) in real time for civilian users, which implements a high-precision service based on high-precision PPP (precise point position) technology in absolute mode. Currently, high-precision PPP technology does not provide for the transmission of precise UTC(SU) or GNSS system time to users.

Objective. Based on the GLONASS system data, to evaluate the attainable accuracy of precise time transmission using PPP technology and propose necessary improvements to the SVO EVI system to implement additional functionality for transmitting UTC(SU) and GNSS system time.

Results. The feasibility of precise time transmission using PPP technology was assessed, and the evaluation of accuracy was estimated, demonstrating the value of no more than 0.2 ns (standard deviation). Necessary improvements to the algorithms and operation of the SVO EVI system to enable the system to implement additional functionality of precise time transmission were identified. These improvements include providing, as part of the assistance data, corrections to the onboard time scales (OTS) of the spacecraft, calculated directly relative to the GET-1 time scale. This will ensure high-precision determination of UTC(SU) time in an absolute mode, both in post-processing and in real-time. Expanding the composition of the assistance data by incorporating information on the deviation of the GLONASS space system time scale relative to UTC(SU) will provide direct access to the GLONASS system time.

Practical Relevance The additional functionality of the SVO EVI will expand the range of high-precision services, enabling not only high-precision positioning, but also transfer of UTC and GLONASS system time.

Shupen K.G., Braginets V.F., Meshcheryakov V.M. Transmission of UTC time and GNSS system time when implementing absolute high-precision positioning using PPP technology and real-time ephemeris and time information. Radiotekhnika. 2025. V. 89. № 12.
P. 25−35. DOI: https://doi.org/10.18127/j00338486-202512-03 (In Russian)

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