Analysis, modeling and simulation of GPS satellite clock errors

Abstract

The satellite clock error is an essential error source for a navigation satellite system. This paper analyses the noise characteristics of the Rb/Cs clocks onboard GPS satellites based on IGS observations, and establish the model of clock error simulation. First, different Rb/Cs clocks are characterized and analyzed using modified Allan variance in the time-domain. Next, the time offset, frequency offset and linear frequency drift parameters are determined using a piecewise least-square polynomial fitting method. And the residual random noises after the polynomial fitting are modelled by a power law spectrum. Finally, an Allan variance decomposition and inversion method is proposed to generate the independent random sequence and then the sequences are superposed together. The synthesized clock error sequence is compared with the original data to validate the modeling and simulation methodology.