为提高星敏感器仿真系统的精度,提出了基于高斯规律的模拟星像点的灰度扩散方法和高斯质心提取算法。按照二维高斯分布规律置灰度值来模拟星像点像素,对称中心是映射坐标而不是取整的中心像素坐标,以便准确模拟实际星像点散焦及像差导致的灰度扩散。高斯质心提取亚像素定位过程包括像素粗定位和偏差精定位两个步骤,基于高斯规律建立了一个分段函数实现偏差精定位。在星像点噪声为N(0,1.22)的仿真条件下,整个偏差区间[-0.5,0.5)pixel内高斯质心定位标准差为0.007 pixel,远小于灰度重心法的0.041 pixel和加权灰度重心法的0.026 pixel,而3种方法对模拟星图的处理结果一致。仿真实验表明:模拟星像点高斯灰度扩散法是合理准确的,而高斯质心提取算法简单精确,精度高于传统灰度重心法。

In order to improve the precision of the simulation system in a star sensor,this paper presents a gray pervasion method based on a Gaussian law for precisely simulating star spots and a Gaussian centroid extraction algorithm.The gray vaiues of simulating star image pixels are evaluated according to the 2D Gaussian distribution law and the mapping coordinates instead of the central pixel round coordinates are taken as the symmetric center,so as gray pervasion phenomenon caused by defocusing and aberration from an actual star spot can be simulated precisely.The new Gaussian centroid extracting sub-pixel positioning method consists of two steps.One is rough pixel-level positioning and the other is fine deviation positioning.A piecewise defined synthesized function is constituted based on Gaussian law to realize the sub-pixel fine deviation positioning.Under the simulating condition of image Gaussian noise in N(0,1.22) and the whole deviation interval of [-0.5,0.5) pixel,the Gaussian centroid positioning precision is 0.007 pixel,which is far less than 0.041 pixel from the gray-weighted centroid method and 0.026 pixel from the square-gray weighted centroid method.After disposing the simulation star map,the conclusions show that the Gaussian gray pervasion method for simulation star spots is rational and accurate,and Gaussian centroid extracting method has a higher precision than those of traditional gray-weighted centroid methods.