Sun Ting, Xing Fei, Wang Xiaochu, Li Jin, Wei Minsong, You Zheng
Appl Opt. 2016 Dec 20;55(36):10335-10340. doi: 10.1364/AO.55.010335.
Benefiting from rapid development of imaging sensor technology, modern optical technology, and a high-speed computing chip, the star tracker's accuracy, dynamic performance, and update rate have been greatly improved with low power consumption and miniature size. The star tracker is currently one of the most competitive attitude measurement sensors. However, due to restrictions of the optical imaging system, difficulties still exist in moving star spot detection and star tracking when in special motion conditions. An effective star tracking method based on optical flow analysis for star trackers is proposed in this paper. Spot-based optical flow, based on a gray gradient between two adjacent star images, is analyzed to distinguish the star spot region and obtain an accurate star spot position so that the star tracking can keep continuous under high dynamic conditions. The obtained star vectors and extended Kalman filter (EKF) are then combined to conduct an angular velocity estimation to ensure region prediction of the star spot; this can be combined with the optical flow analysis result. Experiment results show that the method proposed in this paper has advantages in conditions of large angular velocity and large angular acceleration, despite the presence of noise. Higher functional density and better performance can be achieved; thus, the star tracker can be more widely applied in small satellites, remote sensing, and other complex space missions.
得益于成像传感器技术、现代光学技术和高速计算芯片的快速发展，星敏感器的精度、动态性能和更新速率得到了极大提升，同时具备低功耗和小尺寸的特点。星敏感器是目前最具竞争力的姿态测量传感器之一。然而，由于光学成像系统的限制，在特殊运动条件下进行运动星点检测和星跟踪仍存在困难。本文提出了一种基于光流分析的星敏感器有效星跟踪方法。基于相邻两幅星图像之间的灰度梯度分析基于斑点的光流，以区分星点区域并获得准确的星点位置，从而使星跟踪在高动态条件下能够保持连续。然后将获得的星矢量与扩展卡尔曼滤波器（EKF）相结合进行角速度估计，以确保星点的区域预测；这可以与光流分析结果相结合。实验结果表明，本文提出的方法在存在噪声的情况下，在大角速度和大角加速度条件下具有优势。可以实现更高的功能密度和更好的性能；因此，星敏感器可以更广泛地应用于小卫星、遥感和其他复杂空间任务。
