ESA GNC Conference Papers Repository
Low-level image processing for detecting faint asteroid in the Hera mission
State-of-the-art image sensors and processing techniques are key enabling technologies for future planetary exploration missions. Hera is a European Space Agency mission aiming a binary asteroid system Didymos and Dimorphos. The mission requires an image sensor and processing technique capable to detect its target from a far distance. During the cruise, the main optical instrument Asteroid Facing Camera (AFC) - will acquire several images with the faint target in the field of view. On ground, AFC images will be processed to detect the asteroid and to enhance prior knowledge of the asteroid ephemeris from ground astrometry. This paper presents an algorithm capable to enhance the AFC camera performances and detect faint targets with a magnitude of 8.5, where the limiting magnitude of state-of-the-art star trackers is between 5.5 and 6. High performance of the image processing is achieved through detail analysis of AFC end-of-life noise and its dedicated filtering techniques. Noise identification is performed on an artificially degraded AFC detector (FaintStar II). It includes a detailed analysis of fix-pattern noise (FPN), dark current non-uniformity (DCNU), random telegraph signal (RTS), saturated/dead pixels and baffle straylight background non-uniformity. The processing consists of FPN and DCNU compensation, RTS pixels identification and compensation, attitude estimation and stars removal. The performance of the algorithm is estimated based on artificially generated images and representative night-sky images acquired by the AFC engineering model.