The purpose of this paper is the study of instability clock applicable to the coordinate-time determination based on satellite navigation technologies. The author considers the developed method of estimation and control of time-frequency parameters of GLONASS navigation field. Results of evaluation are departures onboard time scales obtained as a result of trajectory measurements with metrology items State service of time, frequency, and determine the parameters of the Earth's rotation (Moscow, Novosibirsk, Irkutsk).