一种星敏感器主点和焦距的加权在轨标定方法

Weighted on-orbit calibration method of principal point and focal length for star sensor

星敏感器作为卫星姿态测量装置,其在轨服役过程中,主点和焦距的标定精度是影响其姿态输出精度的主要因素。针对标定过程中含有随机测量噪声偏大的星像点,导致星敏感器主点和焦距的标定结果产生较大偏差的问题,提出了一种星敏感器主点和焦距的加权在轨标定方法。该方法首先建立了星敏感器在轨标定模型,然后引入合理的标定权值,加入到最小二乘估计主点和焦距的过程中,寻找并剔除随机测量噪声偏大的星点,最后将加权估计出的结果作为测量,采用扩展卡尔曼滤波对星图进行处理。仿真结果表明,在星点位置存在较大误差的情况下,该方法能剔除随机测量噪声偏大的坏点。星内角距统计偏差约为传统方法的1/10,与真值相比标定参数精度分别为0.219 9像素、0.148 7像素、3.38μm。

As a satellite attitude measurement device, the calibration accuracy of the star sensors principal point and focal length serves as the main factor affecting the accuracy of its attitude output during the onorbit service procession. If the calibration process contains the star image point with large random measurement noise,this will lead to large deviation of the calibration result of the star sensors main point and focal length. Aiming at this problem, a weighted onorbit calibration method of principal point and focal length for star sensor was proposed. Firstly, the method established the onorbit calibration model of the star sensor.Then we added a reasonable calibration weight to the least squares estimation. In this way, we found and removed the points with large random measurement noise. Finally, the weighted leastsquares estimation result was served as the measurement, and the extended Kalman filter was used to process the star image. The simulation results show that, if there is a large error in the position of the star point, this method can remove the bad points where the random measurement noise is too large. The statistical deviation of the angular distance is about 1/10 of the traditional method. Compared with the true value, the accuracy of the calibration parameters is 0.219 9 pixel,0.148 7 pixel and 3.38 μm,respectively.