Preface

International audienceThe Project for On-Board Autonomy 2 (PROBA2) mission has been in orbit 3.5 years and has evolved from a successful technology demonstration platform to a solar-science observatory and will soon become a space-weather monitoring mission. Few satellites have been so versatile in use; this is all the more remarkable knowing that PROBA2 is only a cubicmeter in size, low-budget micro-satellite. Nobody could have guaranteed its broad popularity during the Summer of 2002, when researchers at the Royal Observatory of Belgium replied enthusiastically to ESA's call for instruments onboard the second satellite in the PROBA program. In that year, solar maximum was in full swing and ESA was preparing for a European wide "Space Weather Applications Pilot Project". At the Centre Spatial de Liège and the Royal Observatory of Belgium, people were working on the design of a suite of large EUV imagers called Magritte with an innovative off-axis telescope layout. Also innovative sensors and new non-silicon detectors were being studied in technological projects such as the Blind to the Optical Light Detector (BOLD) program