调制传递函数(Modulation Transfer Function,MTF)是光学卫星相机成像质量评价的重要参数之一,在轨MTF检测关系到遥感数据的应用和未来遥感相机的发展。针对目前对地观测中广泛应用的光电成像系统,以反射点源阵列、辐射状靶标和大面积刃边靶标等便于数学描述的特殊点线面目标作为参照,依据MTF的物理定义,通过亚像元位置检测与参数化模型拟合等,对卫星相机进行了在轨MTF检测。实验结果表明:点源法是最严密的检测方法,可以全面表征遥感相机的成像能力;方波法在大面积靶标配合下,能直接获取成像系统在奈奎斯特频率处的MTF值;刃边法是光学相机常用的检测方法,但是仅能获取沿轨与垂轨方向的MTF。三种方法所得的在轨MTF的检测结果具有较好的一致性,最大相对误差优于6.00%。这些方法各有特点,其适用性存在一定差异。

Modulation transfer function (MTF) is one of the important parameters for the image quality evaluation of optical satellite cameras. On-orbit MTF estimation has a bearing on the application of remote sensing data and the future development of remote sensing cameras. For the photoelectric imaging system widely used for earth observation at present, according to the physical definition of MTF, the satellite cameras are subjected to on-orbit MTF estimation through subpixel position detection and parameterized model fitting, during which the special point, line, and plane targets for convenient mathematical description are taken as references, such as reflecting point source arrays, radial targets, and large-area knife-edge targets. The experimental results show that the point source method is the most rigorous estimation approach and can fully characterize the imaging capability of remote sensing cameras. In contrast, with the assist of large-area targets, the square wave method can directly obtain the MTF value at the Nyquist frequency of the imaging system, and the knife-edge method is a common estimation method of optical cameras but can only have access to the MTF in the orbit direction and that perpendicular to the orbit direction. On-orbit MTF values obtained by the above three methods are of good consistency and the maximum relative error is smaller than 6.00%. At the same time, the above methods have their own characteristics and varied applicability.