考虑卫星轨道运动和像移影响的星敏感器星图模拟方法

An Approach to Star Image Simulation for Star Sensor Considering Satellite Orbit Motion and Effect of Image Shift

星图模拟技术是星图识别算法和星敏感器性能测试的基础。提出一种新的高精度星图模拟方法。该方法分为三个步骤:首先,利用两行轨道数据(TLE,Two-Line Orbital Element)与简化常规/深空扰动的近似解模型(SGP4/SDP4)计算出卫星在轨运行参数,进而获得卫星姿态矩阵;然后,根据星敏感器的方位和俯仰角度,确定星敏感器视场中的导航星及星敏感器安装矩阵,利用小孔成像模型,获得导航星在星敏感器成像面的投影位置;最后,为更准确模拟实际星像点的灰度扩散,在考虑卫星运动引起的恒星像移的基础上,按照二维高斯分布规律置灰度值来模拟星像点像素。在此基础上,还详细分析了不同曝光时间下,恒星像移对恒星位置测量的影响。

The technique of the star map simulation is widely used to test star identification algorithms and the performance of star sensor on the ground.A novel approach to star map simulation is put forward in this paper.The simulation procedure consists of three steps： At the first,exact velocity and position of the satellite platform are obtained via the Two-Line Orbital Element（TLE） data combined with the SGP4/SDP4 model;and then an attitude matrix is obtained.At the second,considering the azimuth angle and elevation angle of star sensor,the accurate positions of selected guide stars on the image plane of star sensor are derived by constructing a pinhole model.At the third,gray values for simulating star image pixels are evaluated according to the 2D Gaussian distribution law.In order to simulate the star image accurately and actually,the image shift should be considered.Based on the proposed star image simulation approach,the effects of image shift on star sensor position accuracy are analyzed for different exposure times.