高动态条件下星斑模拟与星点提取方法

Modeling and Detection of Star Spot in High Dynamic Condition

提出了一种高动态条件下星斑模拟及星点目标提取方法。首先,基于黑体辐射建立星点静态像斑模型;其次,基于星体模糊模型和Bresenham直线生成算法生成动态星点像斑模板;再次,利用生成的模板和相关模板匹配法在星跟踪波门内实现星体目标粗定位并进行伪星点剔除;最后,利用质心法在粗定位区域提取星点质心。实验结果表明,该方法能够适应各种长度的曝光时间,并实现星敏感器在3°/s条件下的稳定跟踪。在曝光时间50ms,角速度3°/s的条件下,星对角距误差为10",平均提取率为97%,与传统方法相比,分别提高了78.4%和36.6%。

In high dynamic conditions,the star spot exhibits a tailing phenomenon,which makes it impossible to accurately extract the star point centroid.In the exposure time,the total number of photoelectrons received by the detector does not change,but with the occurrence of the tailing phenomenon,the star energy is dispersed into more pixels,resulting in blurred and broken star point imaging.The tailing,blurring and fracture of the star spot make the traditional method unable to accurately extract the star centroid,which has adverse effects on the attitude determination of the spacecraft.Adjusting the exposure time can shorten the tail length but it will reduce the energy received by the detector,which also makes it difficult to extract the star centroid.Aiming at the above two problems,this paper proposes a method for modeling and detecting of star spot in high dynamic condition.The method is divided into four steps.Firstly,establish the static star spot template based on blackbody radiation.Secondly,generate the dynamic star spot template based on star blur and Bresenham algorithm.Then,search the coarse positioning area of the star target by correlation template matching.Finally,utilize the centroid method to extract the star centroid.Simulation experiments based on stargazing data in the field proved that the simple template generated by Bresenham algorithm and the complex template generated by integration have the same accuracy in extracting the star centroid,but the calculation speed of the former is 500 times that of the latter.Therefore,when using the correlation template matching method to perform coarse star positioning,the simple template generated by the algorithm in this paper is an approximate replacement of the real star spot energy distribution without sacrificing accuracy.The experimental results show that the proposed method can adapt to various exposure time,making the star sensor realize the stable tracking at the angular velocity of 3°/s.When the exposure time is 50ms and the angular velocity is 3°/s,the angular distance error is 10 arcseconds,the average extraction rate is 97%,,which is the increase of 78.4%,36.6%,compared to the traditional method.