Research On Prediction Of Gps Satellite Precise Clock Error Based On Wavelet And Spectrum Analysis

It is very important to analyze the performance of the satellite atomic clocks and use its properties to establish prediction models to forecast clock error. Firstly, this paper analyzes the physical factors of influencing the GPS atomic clocks. Then, analyzes the existed periodicity by using the product of IGS satellite precise clock error, and finally establish a new clock error prediction model. The main contents show as follows:(1) According to the influence of relativistic effects on the satellite clock, The variation of gravity have effects on output frequency of satellite atomic clock when the satellite atomic clock are running along the satellite orbit. Thus, satellite clock error exist periodicity. It is founding that satellite clock error fitting residuals which obtained by using the polynomial model to fit IGS satellite clock error data have periodicity.(2) Introduce the IGS organization, analyze all kinds of products organized and issued by IGS on detail, especially the ephemeris data of GPS satellite. Analyzes the precision of ephemeris data and the time lag of GPS satellite issued by IGS. We decompose satellite clock error fit residuals in four layers using DB5 wavelet. After wavelet noise reduction processing for the four layers, then use spectral analysis to extract main and significant period items. Summarize and analyze the important evaluation index of satellite clock frequency.(3) Compared and analyzed linear model, quadratic polynomial model, Gray model and ARIMA model. Analyzed their advantages and disadvantages of each model.the results showed that:in the long-term forecast, satellite clock error prediction accuracy of the quadratic polynomial is higher; in the short-term forecasting, satellite clock error prediction accuracy of ARIMA model is higher compared to quadratic model and gray model. According to the prediction result of three times satellite clock error, the prediction error of new Block ⅡF satellite is smaller than Block IIA satellite and Block IIR satellite. To the prediction satellite clock error of Block IIF, Ultra-rapid ephemeris forecast model can obtain better result. This paper can gain a better result through physical property of satellite clock and established models.(4) First we explain the principles and procedures of quadratic polynomial model with periodic terms. Use it to forecast the last 24 hours clock error data. Compare and analyze the prediction accuracy between the established model and Ultra-rapid ephemeris satellite clock error. The modified quadratic polynomial prediction model is better than ultra-rapid ephemeris prediction clock error and the accuracy of modified quadratic polynomial model increased 18.73% in 6h,20.27% in 12h and 27.65% in 24h respectively comparing with the Ultra-rapid ephemeris model.