Planck pre-launch status: High Frequency Instrument polarization calibration

¹ LAL, Laboratoire de l'Accélerateur Linéaire, CNRS Université Paris 11, Bâtiment 200, Orsay, France e-mail: cyrille.rosset@apc.univ-paris-diderot.fr
² APC, Astroparticule et Cosmologie, Université Paris Diderot, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
³ LPSC, Laboratoire de Physique Subatomique et Cosmologie, CNRS, Grenoble, France
⁴ IAS, Institut d'Astrophysique Spatiale, CNRS Université Paris 11, Bâtiment 121, 91405 Orsay, France
⁵ Astronomy and Instrumentation Group, Cardiff University, Cardiff, Wales, UK
⁶ LERMA, CNRS, Observatoire de Paris, 61 Avenue de l'Observatoire, 75014 Paris, France
⁷ European Space Astronomy Centre, PO Box 78, 28691 Villanueava de la Cañada (Madrid), Spain
⁸ Observational Cosmology, California Institute of Technology, Mail code: 367-17, Pasadena, CA 91125, USA
⁹ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
¹⁰ LAOG, Laboratoire d'Astrophysique Observatoire de Grenoble, CNRS, Grenoble, France
¹¹ CESR, CNRS, 9 Av. du colonel Roche, BP44346, 31038 Toulouse Cedex 4, France
¹² Department of Physics, Princeton University, Princeton, NJ 08544, USA
¹³ The University of Manchester, JBCA, School of Physics and Astronomy, Manchester M13 9PL, UK
¹⁴ Dipartimento di Fisica, Universitá di Roma “La Sapienza”, 00185 Roma, Italy
¹⁵ Optical Science Laboratory, University College London, Gower Street, WC1E 6BT London, UK
¹⁶ CEA, Service de Physique des Particules, Saclay, France

Received: 3 August 2009
Accepted: 7 April 2010

Abstract

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 (ΔP/T_cmb ~ 4 × 10^-6 for P either Q or U and T_cmb 2.7 K) 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 ~ 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° respectively. Pre-launch ground measurements reported in this paper already fulfill these requirements.