光电二极管的地球反照光校正及卫星姿态估计

光电二极管作为体积小、成本低的太阳敏感器，可以结合地球敏感器进行卫星三轴姿态估计，但是地球反照光对其具有严重的影响，从而限制了其应用，然而地球反照光数学模型应用复杂。针对此问题，首先建立了一种简化的光电二极管量测模型，将地球反照光设成动态偏置项补偿在光电二极管模型中，并将误差建模为混合高斯噪声。然后应用滑窗估计和随机权重策略动态估计和更新模型中的参数。同时，采用多比例因子分别估计各光电二极管的地球反照光影响，并引入Huber影响函数处理异常值，从而提高了算法鲁棒性和参数估计精度。实验结果表明，采用地球反照光校正的光电二极管量测模型和无迹卡尔曼滤波（UKF）算法可实现卫星的高精度姿态估计，三轴姿态精度能达到0.2°~0.3°。 

The earth's albedo correction of photodiodes and satellite attitude estimation

As a small and low-cost sun sensor, the photodiode, combined with the earth sensor, can determinate full three-axis satellite attitude. However, the photodiode is sensitive to the surrounding light sources, such as the earth, which limits its application. The mathematical model of the earth's albedo is complicated. To solve this problem, a simplified measurement model of the photodiode, describing the effects of the earth's albedo as the dynamic bias and deviation as the mixed-Gaussian noise, is established first. Then parameters in the model are online estimated and updated with windowing and random weighting strategies. To improve the accuracy of the parameter estimation and robustness of the algorithm, the multi-scale factors are used to estimate the influence of albedo on each photodiode, and the Huber function is introduced to prevent the outliers. The experimental results show that the high-precision satellite attitude estimation can be achieved by the new measurement model and the unscented Kalman filter (UKF) algorithm, and the three-axis attitude accuracy can arrive at 0.2°-0.3°.