05/03/02
PAUL Jacques	Service d'Astrophysique
CEA-Saclay	PCHE-
91191	Gif-sur-Yvette, France

Presentation 1 : Oral
ECLAIRs: A Microsatellite for the Multiwavelength Observation of the Prompt Emission of Gamma-Ray Bursts (Atelier PCHE)
Jacques PAUL (SAp, CEA-Saclay) and Didier BARRET (CESR, Toulouse) on behalf of the ECLAIRs collaboration
The prompt gamma-ray emission of Gamma-Ray Bursts (GRBs) is currently interpreted in terms of radiation from electrons accelerated in internal shocks in a relativistic fireball. On the other hand, the origin of the prompt (and early afterglow) optical and X-ray emission is still debated, mostly because very few data exist for comparison with theoretical predictions. It is however commonly agreed that this emission hides important clues on the GRB physics and can be used to constraint the fireball parameters, the acceleration and emission processes, and to probe the surroundings of the GRBs. ECLAIRs is a microsatellite proposed to the French Space Agency and entirely devoted to the observation of the prompt optical, X-ray and soft gamma-ray emission of GRBs. For about 100 GRBs per year, independent of their duration, ECLAIRs will provide broad band coverage from a few eV up to a few hundred keV. This unique capability is achieved by combining wide field optical and X-ray cameras sharing continuously a common field of view (1/6th of the sky) with a coded-aperture imaging telescope operating in the soft gamma-ray band to provide the burst trigger and coarse localization. Furthermore, with its mode of operation, ECLAIRs will enable to search for optical and X-ray precursors expected from theoretical grounds and to follow the transition between the prompt and afterglow phases. ECLAIRs is an international mission which relies upon the support of European and American experimental and theory groups. Here we describe the science payload and the mission scenario for ECLAIRs.

---