调制传递函数(Modulation Transfer Function, MTF) 是客观评价遥感器光学系统在轨特性的主要指标之一。为了避免使用地面目标评估气象卫星在轨MTF时, 大气传输对计算结果的影响, 研究了使用月球目标来计算其在轨MTF的方法。选择由风云二号G星扫描辐射计(VISSR) 获取的不受大气传输影响的月球目标遥感图像, 作为刃边法的输入图像来计算VISSR的在轨MTF, 并且根据探测器的不同探元, 划分不同的子图像, 分别计算其MTF特性。实验结果表明, 使用月球目标得到的MTF结果为0.320 1, 而地球目标由于有大气影响MTF结果仅为0.216 4, 月球目标结果明显优于地球目标。且遥感器各探元结果一致性较好, 在连续时间内由同一子图像计算的不同探元的MTF结果的标准差仅为0.013 31, 表明使用该方法评估的MTF具有稳定性。

The modulation transfer function (MTF) is an important indicator that describes the performance of an optical imaging system. To avoid the effect of atmosphere on the measurement readings obtained by the on-orbit MTF on a meteorological satellite, the calculation method considering the lunar limb is investigated. First, we select the moon image obtained by FY-2G/VISSR as the input for the Knife-edge method. Then, we separate the image into sub-images according to different pixels of the detectors. Finally, based on different sets of sub-images, we obtain different results, which can improve the comprehensiveness of the MTF results. The experiments indicate that the result calculated by the Moon image is better than the result from the Earth image, which are 0.320 1 and 0.216 4, respectively. The standard deviation of MTF results from continuous sub-image is 0.013 31, which indicates the stability of performance of the system.