On-orbit Calibration Technology Of Attitude Measurement Instruments

As the most commonly used attitude measurement instruments in inertialtechnology, the precision of star sensor and gyros can directly affect the precisionof attitude determination system. The parameters of star sensor and gyros will beaffected by changes of the working environments on aircraft in space. In order toimprove the accuracy of measurement and the reliability of attitude measurement,it is necessary to conduct on-orbit calibration of the navigation system hourly. Inthis paper, the on-orbit calibration algorithm and determination method of attitudevia star sensor and gyros are mainly studied. The accuracy of the attitudedetermination method is mainly analyzed based on the proposed error model.Firstly, the error sources of the on-orbit calibration in star sensors wereanalyzed, including star point offset error, radial distortion and focal length error.The formation mechanism of these error sources was elaborated by using theprinciple of diagonal distance conservation. The relationship between diagonaldistance error measured by star sensor and star sensor error sources wasestablished. Then the error model of the star sensor on-orbit calibration was built.Based on the linearized error model, the parameters of the error model wereidentified by the method of iterative least square method. Simulation wasconducted to identify the error parameters and the correctness of design wasshown by the simulation results.Second, for the star sensor error model, the aberration of the star relative tothe star sensor was calculated according to motion parameters of the satellite. Theinfluences of aberration on attitude measurement accuracy and on-orbit calibrationaccuracy of star point offset error, coefficient of radial distortion and focal lengtherror were analyzed. The contribution of the star sensor random error on parameteridentification uncertainty was analyzed.Finally, the calibrated star sensor was used to calibrate the gyros errors, thegyro’s bias, the scale factor error and the installation error were calibrated byKalman filter, the correctness of this method was verified by simulation analysis.Attitude determination method based on gyro and star sensor was proposed toimprove the accuracy of the attitude determination system.