Performance Evaluation for On-Orbit Modulation Transfer Function of FengYun-3C Medium Resolution Spectral Imager (MERSI) using Polar Ice and Snow

摘要

Modulation transfer function (MTF) can be used to evaluate spatial quality of an satellite imaging sensor using a sharp edge, a pulse target, or bar pattern target. This investigation evaluates on-orbit MTF performance of FengYun (FY)-3C MERSI with 20 Bands with 1 km and 250 m spatial resolutions using polar ice and snow as a sharp edge, which was launched on September 23 of 2013. The MTF is calculated by using a Fourier transformation on the line spread function (LSF) though a simple differentiation of the edge spread function (ESF). The final MTF Nyqusit frequencies of the most of MERSI Bands along FY-3C flight direction are higher than 0.30, which are satisfy the original design requirements of 0.25 (250 m) and 0.27 (1km). But the Nyquist frequencies of all Bands along FY-3C scanning direction are around 0.13 that are clearly lower than 0.25/0.27. This relatively worse spatial quality of image along FY-3C scanning direction is primarily attributed to the 27% overlapped scan mode of MERSI sensor for every pixel. The objective of design defect in FY-3C MERSI instrument system is to enhance the signal-to-noise ratio (SNR) of scanning image. To overcome the drawback, in future, we will develop some deblurring methods to restore FY-3C/MERSI image along scanning direction.