为了抑制地面标定与在轨工况差异引入的低频误差，提出了一种低频误差在轨补偿方法，基于地面标定求得主点、焦距初始值与畸变系数，筛选出符合条件的星对，以星对角距误差最小为准则，基于扩展卡尔曼滤波方法，实时更新星敏感器的焦距值.与现有的多参数同时更新方法相比，该方法具有更快的收敛速度与更高的鲁棒性.多次观星试验和在轨飞行验证了本方法的有效性，星对角距误差均值减小90%以上，低频误差减小40%以上.

An on-orbit low spatial frequency error compensation method has been proposed to restrain low spatial frequency error brought by the difference between on ground calibration and on-orbit environment. Firstly, principle points, initial value of focal length and distortion coefficients are calculated during on-ground calibration. Then, focal length is updated by extended Kalman filter based on angle distance error minimization criterion using selected star pairs during on-orbit calibration. Faster convergence rate and better robustness has been validated by simulation. Sky tests data and on-board data proved that the mean value of angle distance error can be decreased by more than 90% and the low spatial frequency error decreased by more than 40%.