电路噪声对星敏感器星点定位精度的影响

提出了一种测量星敏感器电路模块带来的图像噪声的方法。在实验室条件下,用星敏感器拍摄多幅背景图像,分析表明:不同背景图像上相同像素的灰度差值代表了电路模块带来的图像噪声,该噪声服从正态分布。模拟产生该正态分布的随机矩阵作为图像噪声加到理想的星点上,采用亚像素细分质心算法计算出带噪声的星点质心坐标,从而得到噪声带来的星点位置偏差。计算结果表明:实验室条件下,星敏感器实测6等星的质心测量精度为1/25 Pixel,而电路噪声将引起1/200 Pixel量级的标准偏差;电路噪声,尤其是DC/DC电源纹波噪声对星敏感器星点定位带来的误差是不容忽视的。

Circuit noise effects on star sensor position accuracy

A method to measure image noise caused by circuit module was introduced. Firstly, many background star maps were taken at laboratory and calculated statistically, and max gray difference of the same pixel was taken for image noise caused by circuit module. The statistical data show that circuit module noise was accorded with normal probability density distribution. Secondly, based on the energy distribution model of ideal star point, a gray matrix of an ideal star of visual magnitude - 6 was calculated. Then star point with circuit image noise was produced with adding random noise matrix of normal distribution to ideal star point. Finally, based on subpixel centroid arithmetic and simulation data, star position error was calculated. The results show that circuit module can bring image noise of normal distribution; For 6 Mv stars at laboratory, this noise can achieve the accuracy level of 1/200 pixel, Compared with the accuracy level 1/25 pixel of actual star position measurement, circuit noise can not be neglected.