The Difference Method: a simple and effective on-board algorithm for space debris detection

Abstract

The Difference Method algorithm is developed within the European Space Agency (ESA) ”Optical In-Situ Monitor” project by the Astronomical Institute of the University of Bern together with Airbus Defence and Space. Main objectives are the autonomous on-board data reduction, consisting of image segmentation and object detection. These steps are critical in order to achieve an effective on-board processing pipeline optimizing the downlink bandwidth usage. Then, complementary analysis regarding astrometry, photometry and debris characterizations can be performed through the related on-ground processing chain. The baseline of the Difference Method is to process two successive exposures and detect moving objects (space debris) by performing a refined frames subtraction. This method is composed of five main parts which are: star detection, frame alignment, frame subtraction, data selection and data compression. This algorithm shows very convincing results. It can process two frames and detect faint debris streaks, down to peak SNR2 in less than 1 second of execution time, fulfilling rigorous requirements concerning on-board computation power, available da ta bandwidth and streaks detection limits.