The Corrections of Sub-picosecond Propagation Time Delays and the Allan Variance of Discontinuous Measurement for the Inter-satellite Time Transfer

Abstract

The asymmetric signal propagation paths between two satellites lead to the unequal time delays at receiving signal time, which should be accurately corrected when solving the clock difference of inter-satellite time transfer. The observation method of clock difference is analysed, the asymmetric signal propagation time delay caused by satellite motion is then derived and reduced, the delay caused by relativistic deflection of light is also calculated using the time transfer function method, and the residual error stability of the propagation time delay correction is evaluated, which improve the correction accuracy of asymmetric signal propagation time delay to 0.1 ps under the current condition of orbit determination. The autocorrelation function representation of Allan variance is extended, and a method of computing the Allan variance error with missing measuring data is proposed based on the statistical method. The effect of missing measuring data on frequency stability calculation of different noises is also analysed. Overall, a systematic correction approach of the propagation time delay and Allan variance with discontinuous measurement for the inter-satellite two-way time transfer has been constructed, which can be used in the clock difference correction of inter-satellite time transfer in the order of ps.