  The magnetic field plays a pivotal role in many fields of Astrophysics. This
is especially true for the physics of the solar atmosphere. Measuring the
magnetic field in the upper solar atmosphere is crucial to understand the
nature of the underlying physical processes that drive the violent dynamics of
the solar corona -- that can also affect life on Earth.
  SolmeX, a fully equipped solar space observatory for remote-sensing
observations, will provide the first comprehensive measurements of the strength
and direction of the magnetic field in the upper solar atmosphere. The mission
consists of two spacecraft, one carrying the instruments, and another one in
formation flight at a distance of about 200m carrying the occulter to provide
an artificial total solar eclipse. This will ensure high-quality coronagraphic
observations above the solar limb.
  Solmex integrates two spectro-polarimetric coronagraphs for off-limb
observations, one in the EUV and one in the IR, and three instruments for
observations on the disk. The latter comprises one imaging polarimeter in the
EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the
low corona, and an imaging spectro-polarimeter in the UV for chromospheric
studies.
  SOHO and other existing missions have investigated the emission of the upper
atmosphere in detail (not considering polarization), and as this will be the
case also for missions planned for the near future. Therefore it is timely that
SolmeX provides the final piece of the observational quest by measuring the
magnetic field in the upper atmosphere through polarimetric observations.
