  The CMB polarization promises to unveil the dawn of time measuring the
gravitational wave background emitted by the Inflation. The CMB signal is
faint, however, and easily contaminated by the Galactic foreground emission,
accurate measurements of which are thus crucial to make CMB observations
successful. We review the CMB polarization properties and the current knowledge
on the Galactic synchrotron emission, which dominates the foregrounds budget at
low frequency. We then focus on the S-Band Polarization All Sky Survey
(S-PASS), a recently completed survey of the entire southern sky designed to
investigate the Galactic CMB foreground.
