The C-Band All-Sky Survey (C-BASS): Design and capabilities
  The C-Band All-Sky Survey (C-BASS) is an all-sky full-polarisation survey at
a frequency of 5 GHz, designed to provide complementary data to the all-sky
surveys of WMAP and Planck, and future CMB B-mode polarization imaging surveys.
The observing frequency has been chosen to provide a signal that is dominated
by Galactic synchrotron emission, but suffers little from Faraday rotation, so
that the measured polarization directions provide a good template for higher
frequency observations, and carry direct information about the Galactic
magnetic field. Telescopes in both northern and southern hemispheres with
matched optical performance are used to provide all-sky coverage from a
ground-based experiment. A continuous-comparison radiometer and a correlation
polarimeter on each telescope provide stable imaging properties such that all
angular scales from the instrument resolution of 45 arcmin up to full sky are
accurately measured. The northern instrument has completed its survey and the
southern instrument has started observing. We expect that C-BASS data will
significantly improve the component separation analysis of Planck and other CMB
data, and will provide important constraints on the properties of anomalous
Galactic dust and the Galactic magnetic field.
