  The discovery of X-ray emission from cosmic sources in the 1960s has opened a
new powerful observing window on the Universe. In fact, the exploration of the
X-ray sky during the 70s-90s has established X-ray astronomy as a fundamental
field of astrophysics. Today, the emission from astrophysical sources is by
large best known at energies below 10 keV. The main reason for this situation
is purely technical since grazing incidence reflection has so far been limited
to the soft X-ray band. Above 10 keV all the observations have been obtained
with collimated detectors or coded mask instruments. To make a leap step
forward in X-ray astronomy above 10 keV it is necessary to extend the principle
of focusing X ray optics to higher energies, up to 80 keV and beyond. To this
end, ASI and CNES are presently studying the implementation of a X-ray mission
called Simbol-X.
  Taking advantage of emerging technology in mirror manufacturing and
spacecraft formation flying, Simbol-X will push grazing incidence imaging up to
80 keV and beyond, providing a strong improvement both in sensitivity and
angular resolution compared to all instruments that have operated so far above
10 keV. This technological breakthrough will open a new high-energy window in
astrophysics and cosmology. Here we will address the problematic of the
development for such a distributed and deformable instrument. We will focus on
the main performances of the telescope, like angular resolution, sensitivity
and source localization. We will also describe the specificity of the
calibration aspects of the payload distributed over two satellites and
therefore in a not "frozen" configuration.
