Research On On-orbit Calibration Of Star Sensor Based On Temperature Variation

Star sensor is a kind of high precision attitude sensor,which has become one of the necessary navigation equipment on spacecraft.The accuracy of optical system parameters is an important factor affecting the navigation accuracy of star sensor.In general,the star sensor has been calibrated on the ground before using.However,the ground calibration is usually in the normal temperature and pressure environment,while the navigation environment of the star sensor is in the deep space where the temperature changes dramatically.The huge difference of calibration environment will change the optical parameters of the star sensor.In addition,the vibration in the launching process will also make the intrinsic parameters of the star sensor deviate,therefore,it is necessary to update the parameters in real time to obtain the best performance.This paper mainly studies the on-orbit calibration method of star sensor in the environment of temperature change,respectively from two aspects of on-orbit calibration method and the calibration method under the condition of temperature change.(1)The research status of star sensors on-orbit calibration is introduced.The camera model and frames,calibration model of star sensor,working principle and the effect of temperature change on optical of star sensor are introduced.(2)According to the characteristic that the singular value of the star vector is invariant under coordinate transformation,the singular value is used as a new calibration reference to research.Then a calibration method based on singular value decomposition(SVD)is proposed,and the method is optimized to improve the calibration accuracy and parameter convergence speed.(3)On the basis of conventional star angular distance(AD)method,an on-orbit calibration method based on star angular distance subtraction(ADS)is proposed.By improving the observability of the principal point in the calibration process,the on-orbit calibration accuracy of the principal point is improved.Finally,four improved star angular distance subtraction methods are proposed to solve the time-consuming problem of star angular distance subtraction method.(4)Based on the on-orbit calibration method of star sensors,the parameters calibration of star sensors under the condition of temperature variation is studied,and a coupling calibration method is proposed to reduce the influence of temperature change on the parameter calibration of optical system by compensating the parameters.Finally,the shortcomings of the direct superposition are analyzed,and the effectiveness of the coupling method is verified through experiments.