Т.А. Marareskul, А.К. Grechkoseyev, А.V. Vasilenko

Thestrategic aim to achieve the GLONASS service competitiveness with existing and perspective foreign analogues dictatesthe need for enhancement of the GLONASS frequency-time support. One of the possible ways to improve the accuracy of onboard time scales (TS) synchronization is to use the inter-satellite radio links between navigation space vehicles (NSVs). At present, several NSVs of the GLONASS orbital group arealready equipped with onboard equipment for inter-satellite measurements which allowsto carry out the mutual pseudorange measurementsand the digital information exchange between them. It allowed to perform anexperiment and to obtain the estimates of the potentially achievable accuracy of the onboard time scales synchronization of GLONASS NSVs. Thesynchronizationprocesswas based onthe hourly calculation of NSV time scalebindingparameterstotheorbital TS.The orbital TS is formed on the basis of the physical time scale of the leadNSV. The value of error of the mutual TS synchronization of NSVs pairs observed in the experiment is several times less than the analogous value characterizing time-frequency corrections in GLONASS navigation messages currently transmitted. This circumstance allows to recommend the offered technology of the time-frequency corrections in the NSV-s navigation message for use in the GLONASS frequency-time support. To implement this technology it is necessary to equipthe GLONASS space vehicles with onboard equipment for inter-satellite measurements and continue the in-orbit validation of onboard software procedures to confirm the robustness and the required level of operational reliability.