  We have analyzed the available polarization surveys of the Galactic emission
to estimate to what extent it may be a serious hindrance to forthcoming
experiments aimed at detecting the polarized component of Cosmic Microwave
Background (CMB) anisotropies. Regions were identified for which independent
data consistently indicate that depolarization must be small. The power
spectrum of the polarized emission, in terms of antenna temperature, was found
to be described by $C_{\ell}\simeq (1.2\pm 0.8)\cdot 10^{-9}\cdot (\ell /
450)^{-1.8\pm 0.3}\cdot (\nu/ 2.4{\rm GHz})^{-5.8}$ K$^{2}$, from arcminute to
degree scales. Data on larger angular scales ($\ell\le 100$) indicate a steeper
slope $\sim \ell^{-3}$. We conclude that polarized Galactic emission is
unlikely to be a serious limitation to CMB polarization measurements at the
highest frequencies of the MAP and {\sc Planck}/LFI instruments, at least for
$\ell\ge 50$ and standard cosmological models. The weak correlation between
polarization and total power and the low polarization degree of radio emission
close to the Galactic plane, found also in low-depolarization regions, is
interpreted as due to large contributions to the observed intensity from
unpolarized sources, primarily strong HII regions, concentrated on the Galactic
plane. Thus estimates of the power spectrum of total intensity at low Galactic
latitudes are not representative of the spatial distribution of Galactic
emission far from the plane. Both total power and polarized emissions show
highly significant deviations from a Gaussian distribution.
