Research On Theroy And Method Of On-orbit Calibration For Navigation Constellation Inter-satellite Measurements

The inter-satellites link(ISL)is an effective way to improve the service performance of navigation satellite system,and it has been equipped in the world's major navigation satellite systems or in the plan to be done.ISL with narrow beam TDMA system,which shows high ranging accuracy,fast communication speed,strong anti-interference ability and low power consumption,has lead the trend of ISL in navigation satellite system.By applying ISL to promote the service capability of the navigation satellite system,the autonomous navigation can be achieved with less reliance of the navigation system on the ground segment and the autonomous integrity monitoring can be secured.Once the anomaly occurred in the inter-satellite measurement,the functions mentioned above could be affected,and even led to the interruption of global navigation,positioning and timing service of Beidou-3 navigation satellite system in severe cases.Hence it is critical to guarantee the validity of inter-satellite measurement.However,affected by the space environment,satellite reliability and relative position between satellites,the abnormal inter-satellites measurement will inevitably appear..So before it utilized,the quality of inter-satellites measurement data requires evaluation.Under autonomous navigation mode,the satellite is separated from the ground segment,and the evaluation should be accomplished based merely on its own on-orbit.In this circumstance,this thesis studies the theory and method of how the navigation constellation can calibrate the inter-satellite measurement utilizing onboard resources in autonomous navigation.Based on this basic problem,the following four key technical issues are addressed:1.Focusing on slot planning of time-division narrow beam ISL,an ISL slot planning method based on packet multiplexing and step optimization is proposed.According to the ISL structure and the visibility between the satellite and the earth,the inter-satellite slot connection relationship is optimized by grouping multiplexing and stepwise optimization.The planning results show that the performance requirement of Beidou-3 navigation satellite system can be satisfied when the slot occupancy rate is lower than 50%.2.A calibration benchmark generation method based on the slowly changing characteristics of ephemeris error is presented to solve the reference problem of intersatellite measurement in-orbit calibration.The inter-satellite calibration reference is raised utilizing the slow variation of ephemeris error for subsequent measurement.On this basis,the reference accuracy is analyzed from three aspects of geometry configuration,link number and ranging accuracy.According to the analysis,the accuracy is improved by one order of magnitude compared with the calibration data obtained directly from broadcast ephemeris,and it can meet the precision requirement of intersatellite measurement on-orbit calibration.3.Focusing on the anomaly detection in calibration error sequence of inter-satellite measurement,a fault detection method based on synthetic time frequency analysis is raised.According to the statistical and spectral characteristics of the calibration error sequence,the anomaly detection benchmark is constructed,and then the anomaly classification and characteristics in inter-satellites measurement can be obtained based on anomaly sources.The results show that the false alarm probability is 0.0474%,and the success rate of comprehensive detection for different anomalies exceeds 96%.4.A method based on multidimensional wavelet feature analysis is proposed for the anomaly location in calibration error sequence of inter-satellite measurement.The anomaly is located by the features of scale spectrum matrix,time energy spectrum,reconstruction sequence.Then the process and strategy of on orbit calibration for inter satellite measurement are given.The test results show that the success rate of comprehensive positioning for different anomalies is more than 98%,and the accuracy of abnormal positioning is over 94%.Theoretical deduction and simulation analysis are conducted to prove the validity and correctness of the research results above.It is of great significance to the construction of ISL in China's navigation satellite system as a reference.