An Research On Key Technologies Of Precise Orbit Determination Of Cis-lunar Spacecraft Based On Spaceborne GNSS

With the continuous development of Chinese lunar exploration missions,the number of cis-lunar spacecraft continues to increase and the on-orbit time is gradually extended,leading to higher requirements for orbit determination performance.Depending solely on traditional ground-based measurement systems will be difficult to meet mission the requirements in terms of both cost and precision.Global navigation satellite systems have lower requirements for on-board equipment and can achieve high-precision autonomous positioning and navigation relying solely on on-board devices without the need for a global station network.They can also supplement ground-based measurement systems to improve mission reliability and have significant advantages in improving navigation autonomy and orbit precision for cis-lunar spacecraft.However,the application of GNSS navigation technology in cis-lunar space faces challenges such as a small number of visible satellites,poor satellite geometry configuration and weak signal strength.Therefore,it is necessary to comprehensively analyze the availability and data characteristics of GNSS in cis-lunar space and study precise orbit determination technology based on spaceborne GNSS receiver to provide technical support for Chinese future lunar exploration missions.To this end,this thesis focuses on the application of spaceborne GNSS in cislunar spacecraft and conducts research from three aspects: availability analysis,cycle slip detection and orbit determination.The main research content and contributions are as follows:(1)To deeply analyze the application characteristics of GNSS in autonomous navigation of cis-lunar spacecraft,this thesis simulates and analyzes the availability of GNSS in cis-lunar space comprehensively from three aspects: the number of visible satellites,signal visibility,PDOP,and signal dynamic characteristics,taking the lunar transfer orbit and lunar orbit as examples.Based on this analysis,this thesis summarizes and proposes the technical challenges that cis-lunar spacecraft faces in utilizing GNSS signals.(2)Based on the characteristics of large observation data noise,short arc,and many cycle slips in GNSS observation data for cis-lunar spacecraft,this thesis proposes three cycle slip detection methods based on Kalman filtering,which provide indispensable prerequisites for subsequent precise orbit determination.To address the issue that the effect of Kalman filtering on GNSS data varies with different differential orders,this thesis proposes a Kalman filtering cycle slip detection method based on adaptive differential order.To address the issue that the convergence of robust Kalman filtering cycle slip detection method is difficult due to the short arc of carrier phase data,this thesis improves the adaptive robust Kalman filtering cycle slip detection method.To address the problem of low measurement accuracy of observation data,this thesis proposes a cycle slip detection method based on Kalman filtering and smoothing of Doppler values.(3)Taking the application of on-board GNSS in the re-entry and return test mission of Chinese CE-5T1 mission as an example,this thesis thoroughly discusses its differences from ground-based and near-earth GNSS applications from the perspective of data characteristics,formulates an appropriate orbit determination strategy,completes the actual orbit determination calculation,and achieves a threedimensional RMS of 19.91 m for the overlap arc of single GPS observation data with a 5-second sampling interval,and 15.60 m for the overlap arc of GPS+GLONASS observation data with a 5-second sampling interval.There are 37 figures,15 tables,and 102 references in this thesis.