  ECLAIRs is a French microsatellite devoted to the observation of the prompt
optical and X-ray emission of GRBs. For about 100 GRBs/yr, independent of their
duration, ECLAIRs will provide high time resolution high sensitivity spectral
coverage from a few eV up to ~50 keV and localization to ~5 arcsec in near real
time. This capability is achieved by combining wide field optical and X-ray
cameras sharing a common field of view (~1/6th of the sky) with the coded-mask
imaging telescopes providing the triggers and the coarse localizations of the
bursts. Given the delays to start ground-based observations in response to a
GRB trigger, ECLAIRs is unique in its ability to observe the early phases (the
first ~20 sec) of all GRBs at optical wavelengths. Furthermore, with its mode
of operation, ECLAIRs will enable to search for optical and X-ray precursors
expected from theoretical grounds. Finally ECLAIRs is proposed to operate
simultaneously with GLAST on a synchronous orbit. This combination will ensure
broad band spectral coverage from eV to GeV energies for the GRBs detected by
the two satellites, ECLAIRs further providing their accurate localization to
enable follow-up studies.
