[en] Proba-II (Project for On-board Autonomy) is an ESA microsatellite development for a launch early in 2006. Aiming at technology demonstration, PROBA-2 will embark a scientific payload dedicated to Sun observations and monitoring, and innovative platform subsystems with new advanced technologies suchas propulsion systems with cold gas generator, Li-Ion batteries, stellar compass and reaction wheels,solar array with concentrator, new central processor... The overall PROBA-2 mission includes a majorBelgian contribution, on both platform and payload sides, and also on the ground segment part.The payload will contain the Thermal Plasma Measurement Unit and the Dual Segmented LangmuirProbe for Space environment on one side, and the Sun Watcher using Active Pixel System detector andimage Processing (SWAP) and the Lyman alpha Radiometer (LYRA) for Sun observation on the otherside. The solar payload will provide space weather informations with an overall survey of the solarcorona. Additionally, warnings will be raised in nearly real time with specific watch of coronal massejections with the SWAP imaging telescope.This paper details the mission and will focus on the Belgian-led payload science instruments and theirscientific objectives. It shows how it was possible to take benefit of a technological mission and toprioritize some of the science outcomes.
