Real-time High-precision Relative Position Of Formation Flying Satellites Onboard GPS

Many small satellites formation flight instead of single large satellite is an important development trend in the field of space,but also to achieve InSAR and gravity field inversion and other scientific tasks of the key technology,and the relative positioning of small satellites is determined to form the flight mission to achieve these scientific tasks The premise.The real-time and high-precision relative orbit determination technology of fleet formation can meet the real-time performance of the mission and the premise of the future technology of transmitting and dispatching space-based radar and virtual antenna array.The study of real-time high-precision relative orbit determination is relatively late,and the short-range formation real-time orbit determination is still in the stage of using pseudo-range observation.For medium-length baseline,it is still in the simulation verification stage.In-depth study.Therefore,under the constraint of dynamic model,the GRACE satellite data with the orbital height of 460km-480km and the baseline length of about 190km are taken as an example.Based on single-phase ionospheric phase observation and UD filter,high-precision real-time relative Rail,for the relevant research and engineering applications provides a reference.In order to achieve the above purpose,this paper has carried on the detailed research to the three key problems that affect the real-time relative orbit:First,the analysis of the influence of the relative orbit results of the observation error,including the ionospheric error,broadcast ephemeris error,The reference station position error,the receiver clock error;the second is through the absolute mechanical model to get the difference between the "relative mechanical model" to control the quality of the observed value,the relative track accuracy;Third,the design optimization of the parameter estimation strategy,Based on the UD filter,the RTN direction compensation acceleration of the first order Gaussian Markov process is used to compensate the shortcomings of the relative mechanical model,and the relative receiver clock difference is approximated by the random walk process.The specific research contents and conclusions are as follows:(1)The observation model,observation error,mechanical model and data preprocessing method of real-time relative orbit are studied systematically.The existing methods of relative orbit determination are compared,and the advantages and disadvantages of the single difference phase method are described.Then,the realization scheme of the single-phase phase observation is taken as the real-time relative orbit observation model.The ionospheric delay error,Ephemeris error,reference station position error,receiver clock error and so on on the accuracy of the relative orbit determination accuracy,and then analyzed under the influence of the current error to achieve high precision real-time relative orbit of the possibility of research given real-time relative The results show that in order to achieve high precision relative orbit determination,the order of gravity field should not be less than 30x30,and the step should not exceed 30s.The results show that in order to achieve high precision relative orbit determination,This paper introduces the method of pseudo-range gross error detection and phase-cycle detection,which is suitable for single-difference observation,and uses the relative mechanical model to analyze the pseudo-range observations and carrier observation for the characteristics of real-time relative orbit Value for quality control.(2)The real-time relative orbit determination software based on single difference phase model and UD filter is realized.The real-time relative orbit simulation calculation and analysis are carried out based on broadcast ephemeris and GRACE A/B satellite formation data.The results show that the GRACE real-time relative orbit three-dimensional position accuracy is 0.55m,0.41m,0.11m,respectively,using the direct difference method,single difference pseudorange method and single difference phase method,respectively,compared with JPL's post-precision track The accuracy of the R,T,and N directions in the three directions is 5cm,6cm,7cm,and the international use of the radio ephemeris without ionosphere The accuracy of the carrier phase difference method is equivalent.(3)Based on the comparative analysis,the strategy of relative orbit determination is optimized.In order to give the optimal processing strategy suitable for GRACE real-time relative orbit determination,this paper analyzes the initial variance of the compensation acceleration and the correlation time of the first-order Markov process and the steady-state variance by designing a number of different experiments,The initial variance of the receiver clock difference and the correlation time of the random walk process,the steady-state variance and other parameters on the real-time relative orbit results.We can draw the following conclusions:First,the compensation acceleration of R,T,N,the initial variance of the receiver clock difference parameter has little effect on the result of filtering convergence,but the initial variance of ambiguity may lead to filtering divergence;The acceleration of the acceleration process has a significant effect on the filtering result,both the steady-state variance and the correlation time increase or decrease,which can lead to the inability to obtain the optimal filtering result.Thirdly,the longer the observation interval is,the worse the filtering result is.The lower the order,the worse the filter results,but the 30x30 order and 50x50 order position accuracy,speed accuracy by 40%.(4)Compare the receiver clockwise random walk model and the clock difference clock speed model,and obtain the clock difference clock speed model can further improve the relative orbit accuracy to 7.7cm;and based on the clock difference clock speed model to solve the long and short baseline,Single-day position accuracy are better than 10cm,speed accuracy is better than 0.12mm/s.