Research On Characteristics And Short-term Prediction Of Gps Satellite Atomic Clock

In the global navigation system,want to get accurate positioning,it must first achieve accurate time measurement.In other words,to establish high accuracy and high stability of the atomic frequency standard and time system has become a high-precision navigation and positioning of the key.As the most accurate timing tool in the world,it is also the core part of the payload of satellite navigation system.Its stability performance directly determines the accuracy of navigation positioning and time-frequency transmission.Long-term characteristics of the analysis,given the satellite clock phase,frequency,frequency drift and stability of the calculation model.In addition,since the clock error forecast is an important basis for achieving time synchronization,it is necessary to establish a high-precision satellite clock error prediction model in the study and in practice,which on the other hand determines the accuracy of satellite navigation and positioning Degree and accuracy.In this paper,based on the theory and research results of atomic clock time-frequency characteristics,this paper explores the characteristics of the time-frequency characteristics of the satellite-borne atomic clock and the problems that are found in the satellite clock error prediction model.The main contents and achievements of this paper include:(1)First,for the GPS in-orbit satellite atomic clock,BLOCK IIR-M and BLOCK IIR,BLOCK IIA,BLOCK IIF,using the commonly used quadratic polynomial model to get the satellite clock difference model,which according to the relevant formula obtained GPS The frequency,frequency drift and residual sequence of the satellite clock are recorded.The stability of Cs and Rb clocks are calculated in turn.This paper uses the overlapping Hadamard variance,which further reveals the phase of the GPS satellite Frequency,frequency drift and residual index changes;found GPS BLOCK IIF satellite clock stability is highest,followed by GPS BLOCK IIR-M and BLOCK IIR Rb clock,and then GPS BLOCK IIA type Cs clock.The worst stability is the GPS BLOCK IIA Rb clock.(2)In the short-term forecast of 6 hours forecasting,we first use less known data.In this paper,24 epochs are used.In terms of forecasting accuracy,the quadratic polynomial model is better than the linear model.The prediction accuracy of the system model is worse;after using 144 epochs as well known data modeling,it is not difficult to find that the prediction accuracy of these three forecast models is not very different,and one of the methods can be selected.From another point of view,by forecasting the forecast accuracy of 24 hours,we can see that the forecast error increases with the increase of forecast time.In summary,the gray system model as a forecast model,it is a very important advantage is the use of less known data,and can get a higher prediction accuracy.With the increase of forecasting time or the increase of the number of forecasting epochs,the accuracy of gray model prediction is much better than that of quadratic polynomial method,which shows that the obvious disadvantage of quadratic polynomial model is its error accumulation characteristic.In this paper,we compare the difference between the predicted value of the clock and the final product of the IGS,and verify the feasibility and validity of the linear model,the quadratic polynomial model and the gray model.These preliminary and empirical conclusions have some reference value and reference significance for real-time precision single point positioning satellite clock error forecast.