Research On Autonomous Integrity Monitoring Of Beidou Satellite Navigation Ephemeris

The accuracy of satellite ephemeris directly affects whether users can obtain accurate positioning services.In the current Beidou system,the guarantee for the integrity of the navigation ephemeris on the satellites is limited to verifying whether the issued ephemeris is consistent with the ephemeris uploaded by the ground station,while the accuracy of the ephemeris uploaded by the ground station itself is not verified.Explore.Based on the historical ephemeris of Beidou satellites,this paper proposes two methods for autonomous integrity monitoring of satellite navigation messages.(1)This article further studies the broadcast ephemeris for the scenario of autonomous integrity monitoring of the satellite navigation ephemeris:First,the calculation accuracy of the broadcast ephemeris calculation time before the reference time₀),that is,the relative time is less than 0,is studied.The results show that the solution within one hour before₀)still maintains a high accuracy.This result shows that the monitoring of the broadcast ephemeris does not need to wait until the arrival of₀),but can be monitored according to the real-time calculated value within one hour before₀),so as to find errors as early as possible;the second point is to pass The analysis of the ephemeris carried out a study on the orbital period of the Beidou satellite.The results show that the Beidou satellite has a periodicity.The MEO period value is about 6 days,23 hours,31 minutes and 40 seconds,and the orbit shape in each period is similar.Use this feature It is also possible to monitor the integrity of the ephemeris.(2)Autonomous integrity monitoring of navigation ephemeris based on inter-satellite links.By calculating the inter-satellite link ranging value of the two satellites and the residual error of the distance between the two satellites calculated by the ephemeris,the two abnormal conditions are analyzed separately:for the sudden change of the orbit,the residual is proposed when the residual is in the normal distribution.When the dynamic threshold is set according to the statistics and the residual does not conform to the normal distribution,the Johnson transformation is used to perform the normal transformation and then the two methods are tested.In view of the gradual deviation of the track,two methods are proposed to set the static threshold according to the statistics and judge the goodness of linear fit of the residual value.(3)Perform autonomous integrity monitoring of the navigation ephemeris periodically based on the satellite orbit.Two different error performances were proposed for monitoring methods:for the sudden change of the orbit,a method of analyzing the orbit residuals at the corresponding time points of the current cycle and the previous cycle and using the ARIMA model to predict the residuals of the detected points was proposed.Judge whether the ephemeris is wrong by comparing the relationship between the predicted value and the ephemeris solution value.In view of the gradual deviation of the track,a method using Euclidean distance and cosine distance to measure the similarity of the track is proposed to verify whether the track is abnormal.