On-orbit modulation transfer function estimation For RASAT

Abstract

RASAT, launched to its sun-synchronous orbit on 19.08.2011, is a 93 kg small satellite carrying an optical imager with Ground Sampling Distances (GSD) 7.5 m for panchromatic and 15 m for multispectral images. Optical imager is composed of a cassegrain telescope and a linear CCD sensor. The Modulation Transfer Functions (MTF) is a quality metric used in remote sensing and very important for characterization of optical imaging systems. In this study, the MTF of RASAT optical imaging system is calculated by using slanted edge method. This method is an image based MTF measurement method that calculates Edge Spread Function (ESF), Line Spread Function (LSF) and MTF, respectively. The ESF is the system response to a high contrast edge. The derivative of the ESF produces the LSF, which is the system response to a high contrast line. The normalized magnitude of the Fourier Transform of the LSF produces MTF. Data processing software is developed under MATLAB to calculate and to plot the ESF, LSF, and MTF graphs.