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The Monitor e Imageador de Raios-X (MIRAX) is a small (~250 kg) X-ray astronomy satellite mission
designed to monitor the central Galactic plane for transient phenomena. With a field-of-view of ~1000
square degrees and an angular resolution of ~6 arcmin, MIRAX will provide an unprecedented discovery-space
coverage to study X-ray variability in detail, from fast X-ray novae to long-term (~several months)
variable phenomena. Chiefly among MIRAX science objectives is its capability of providing simultaneous
complete temporal coverage of the evolution of a large number of accreting black holes, including a detailed
characterization of the spectral state transitions in these systems. MIRAX's instruments will include a soft X-ray
(2-18 keV) and two hard X-ray (10-200 keV) coded-aperture imagers, with sensitivities of ~5 and ~2.6
mCrab/day, respectively. The hard X-ray imagers will be built at the Instituto Nacional de Pesquisas
Espaciais (INPE), Brazil, in close collaboration with the Center for Astrophysics & Space Sciences (CASS)
of the University of California, San Diego (UCSD) and the Institut fur Astronomie und Astrophysik of the
University of Tubingen (IAAT) in Germany; UCSD will provide the crossed-strip position-sensitive (0.5-
mm spatial resolution) CdZnTe (CZT) hard X-ray detectors. The soft X-ray camera, provided by the Space
Research Organization Netherlands (SRON), will be the spare flight unit of the Wide Field Cameras that
flew on the Italian-Dutch satellite BeppoSAX. MIRAX is an approved mission of the Brazilian Space Agency
(Agnecia Espacial Brasileira - AEB) and is scheduled to be launched in 2011 in a low-altitude (~550 km)
circular equatorial orbit. In this paper we present recent developments in the mission planning and design, as
well as Monte Carlo simulations performed on the GEANT-based package MGGPOD environment
(Weidenspointner et al. 2004) and new algorithms for image digital processing. Simulated images of the
central Galactic plane as it would be seen by MIRAX are shown.
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