Planck pre-launch status: High Frequency Instrument polarization
  calibration
  The High Frequency Instrument of Planck will map the entire sky in the
millimeter and sub-millimeter domain from 100 to 857 GHz with unprecedented
sensitivity to polarization ($\Delta P/T_{\tiny cmb} \sim 4\cdot 10^{-6}$) at
100, 143, 217 and 353 GHz. It will lead to major improvements in our
understanding of the Cosmic Microwave Background anisotropies and polarized
foreground signals. Planck will make high resolution measurements of the
$E$-mode spectrum (up to $\ell \sim 1500$) and will also play a prominent role
in the search for the faint imprint of primordial gravitational waves on the
CMB polarization. This paper addresses the effects of calibration of both
temperature (gain) and polarization (polarization efficiency and detector
orientation) on polarization measurements. The specific requirements on the
polarization parameters of the instrument are set and we report on their
pre-flight measurement on HFI bolometers. We present a semi-analytical method
that exactly accounts for the scanning strategy of the instrument as well as
the combination of different detectors. We use this method to propagate errors
through to the CMB angular power spectra in the particular case of Planck-HFI,
and to derive constraints on polarization parameters. We show that in order to
limit the systematic error to 10% of the cosmic variance of the $E$-mode power
spectrum, uncertainties in gain, polarization efficiency and detector
orientation must be below 0.15%, 0.3% and 1\deg\ respectively. Pre-launch
ground measurements reported in this paper already fulfill these requirements.
