In-flight MTF stability assessment of ALSAT-2A satellite

Since the end of the commissioning phase, more than 130,000 imagery products of ALSAT-2A satellite are received to date. This positive assessment of the mission is due to the high performances of the imager system and the permanent in-flight follow-on of the image quality and its calibration. Due to launch vibrations, harsh space environment, change in material properties in time and the drift of the local solar time evolution, many radiometric and geometric calibration campaigns have been conducted. The modulation transfer function (MTF) is one of the most important characteristics carefully estimated in-orbit. It describes the ability of a sensor to resolve the spatial details of an image formed by the incoming optical information. This paper discusses an accurate in-flight measurement of the MTF of the ALSAT-2A images. Also, the evolution of the MTF and its stability since the launch is discussed. The assessment is performed on many panchromatic images of a painted black and white checkboard. The obtained results show that the MTF is still stable and higher than specification.