点扩散函数对星点提取误差分析的影响

星点提取系统误差又称作像元频率误差,它的分布呈现以像元为周期的规律性,分析它的分布规律对补偿这种误差有指导作用。光学系统点扩散函数类型是影响星点提取系统误差分布的主要因素,选取合理的点扩散函数模型对星点提取系统误差进行频域分析,可以减小分析结果与实际的偏离,提高误差补偿效果。传统方法采用Gauss分布点扩散函数模型进行频域分析,但没有考察它的合理性。文中结合星敏感器拍摄的星点像,将一种Giancarlo点扩散函数模型与Gauss点扩散函数模型进行了比较。并在星点提取系统误差频域分析中采用Giancarlo点扩散函数模型,推得星点坐标提取误差理论解析式。与传统频域分析结果相比,文中频域分析结果中引入了对S曲线振幅起调制作用的项,使得星点横坐标系统误差沿x轴呈现S曲线分布的同时,其振幅沿y轴方向发生改变。随后在噪声条件下对星点提取系统误差进行了仿真,仿真结果与频域分析结果相符。最后进行了实验验证,根据理论解析式对结果进行了误差补偿,星点提取精度提高了54.42%,优于传统正弦拟合补偿方法。

Effect of point spread functions on star centroid error analysis

Star centroid systematic error is called pixel frequency error, whose period is the width of the pixel. The analysis of the distribution of systematic error is useful in error compensation. Point spread function is the main factor which affects the distribution of systematic error. Traditionally the Gauss point spread function is used in the frequency analysis of the systematic error, but its reasonability has not been taken into consideration. With real star image considered, the Giancarlo point spread function was compared with the Gauss point spread function. Then the Giancarlo point spread function was used in the spacial frequency analysis of star centroid systematic error, and the theoretical formulas of the systematic error was obtained. Compared with the result of the traditional frequency analysis, an item that modulated the amplitude of the S curve distribution was added to the theoretical formulas, and that made the x coordinate systematic error distributed as an S curve along x axis and the amplitude of S curve changed along y axis. A simulation under a condition with noise was carried out, and the result was in accordance with the frequency analysis of this article. Finally an experiment is done, the result of the experiment is compensated for according to the theoretical formulas, the star centroid accuracy is improved by 54.42%, which is better than the traditional sine curve fitting compensation method.