Research On X-ray Pulsar Autonomous Navigation Method Based On Anomaly Detection

Astronomical autonomous navigation is the key to realize the autonomous operation of spacecraft,it is the core technology to improve the reliability of the navigation,reduce the running cost of monitoring and control,and ensure the space competitiveness in our country.As an important branch of astronomical autonomous navigation,X-ray pulsar navigation has strong anti-interference ability,low precision requirements for navigation sensors and can provide high-precision navigation information such as position,speed,attitude and time for the spacecraft,which is the development direction of China's spacecraft autonomous navigation field.X-ray pulsar navigation using the time difference of the same pulse to the solar system barycenter and the spacecraft as the basic observation of navigation,the optimal state estimation is carried out by filtering method,and then achieve the precise orbit of the spacecraft.But it can't provide continuous navigation information and has a poor real-time performance due to the long navigation filter period.By measuring the Doppler radial velocity of the spacecraft relative to the sun,it can be used as the navigation information for the integrated navigation,and greatly improve the real time of the navigation method.However,the solar spectral distortion makes the Doppler velocity measurement error increases dramatically,causing the decrease of the navigation positioning accuracy,and ultimately lead to the failure of the navigation task.On the other hand,the good period stability of the X-ray pulsar is an important condition to realize autonomous navigation positioning,but some pulsars have the glitch on their autobiography period,which makes the error of the pulsar phase predicted by the pulsar clock model increase,affecting the navigation positioning accuracy.The unpredictability of the pulsar glitch is a potential threat to X-ray pulsar navigation.Aiming at the problem that the solar spectrum distortion affects the precision of pulsar navigation and positioning,a double model Doppler/pulsar integrated navigation method based on anomaly detection is proposed,with this method,whether the solar spectrum is distorted or not is judged by the anomaly detection mechanism so as to decide to adopt Doppler differential velocity measurement or two-dimensional Doppler velocity measurement,therefore the impact of spectrum distortion on Doppler velocity measurement is reduced and the navigation positioning accuracy is ensured,and uses the high precision state information obtained by X-ray pulsar navigation to correct the state information of the Doppler velocity navigation,which can reduce the accumulative error greatly.The simulation results verify the feasibility of the method.Compared with other X-ray pulsar/Doppler integrated navigation methods,the proposed method can resist the influence of spectrum distortion and obtain high accuracy estimation of position and velocity as well.Aiming at the problem of pulsar glitch affecting the accuracy of pulsar navigation positioning,a pulsar autonomous monitoring method against glitch based on anomaly detection mechanism is proposed,which uses the anomaly detection mechanism to judge whether the pulsar glitch occurs,when a glitch have been detected,then enable the alternate navigation pulsar in the next observation period to continue the pulsar autonomous navigation positioning,finally,the extended Kalman filter is used to realize the continuous orbit determination.The simulation results show that the proposed method can effectively eliminate the interference of the pulsar glitch and ensure the accuracy of navigation positioning.