ON-ORBIT MTF ESTIMATION FOR THE KOMPSAT-3A SATELLITE USING STAR IMAGES

摘要

The KOMPSAT-3A (Korean Multi-Purpose Satellite-3A) was successfully launched on 26 March 2015. with the mission to provide high-resolution imagery for civilian and defense users. The modulation transfer function (MTF). which represents the performance of the imaging system in spatial resolution aspect, has been evaluated since calibration and validation phase of the KOMPSAT-3A program and the edge method has been adopted as the nominal method for the estimation of MTF of the KOMPSAT-3A system. Meanwhile star images, which can be treated as the representative of the point spread function, has been obtained for the application on optimization on focusing mechanism. This paper presents methods and results for the estimation on KOMPSAT-3A on-orbit MTF performance using star images observed. The two-dimensional point spread function (PSF) in sub-pixel level was established by integrating of a series of star images and modelling. The MTF and the full width at half maximum (FWHM) were finally evaluated as a function of both vertical and horizontal direction by averaging out for the quantitative estimation. The result shows that the spatial resolution parameters show higher values than those reported by edge method and this deviation is likely to be caused by both the procedural difference such as the application of modelling and the existence of degradation by F.arth's atmosphere. In the aspect of stability, it is concluded that the MTF has been maintained without any noticeable degradation.