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APS像元结构和大小制约APS星跟踪器精度,采用散焦技术使星光成像在几个相邻像素(窗)上,以窗内灰度重心作为星点质心可以得到亚像素定位精度。APS具有多种噪声源,它们直接影响质心定位精度。根据星点模型和质心误差计算模型量化分析了窗大小、星点模型方差、噪声源对APS亚像素质心定位的影响。分析结果表明5×5窗为最优窗,星点模型方差最优值为0.62个像素,精度为0.0016个像素;固定模式噪声、暗电流对质心定位影响较大,读噪声较小,提高信噪比可以改善质心定位精度。
APS pixel structure and size constraints APS star tracker accuracy, defocus technology to make the star image in a few adjacent pixels (windows), the center of gravity window as a star centroid can get sub-pixel positioning accuracy. APS has a variety of noise sources, which directly affect the accuracy of centroid positioning. According to the star point model and the centroid error calculation model, the influence of window size, star point model variance and noise source on APS subpixel centroid location is quantitatively analyzed. The analysis results show that the 5 × 5 window is the optimal window, the optimal variance of the star point model is 0.62 pixels and the precision is 0.0016 pixels. The fixed mode noise and dark current have greater influence on the centroid location, Noise ratio can improve the centroid positioning accuracy.