The low frequency instrument on-board the Planck satellite: Characteristics and performance

Planck is the third generation space mission, after COBE/DMR and WMAP, devoted to image the CMBR anisotropies. The low frequency instrument (LFI) will simultaneously observe the sky in three frequency bands centered at 30, 44 and 70 GHz. It is composed by 11 pseudo-correlation receivers, actively cooled to 20 K, able to detect both orthogonal polarisation of the incoming signal. The LFI will be located, along with the high frequency instrument (HFI), in the focal region of a 1.5 m aperture telescope. The LFI will produce full-sky maps of the anisotropies of the CMBR with a FWHM angular resolution of 33′, 27′ and 14′ for the 30, 44 and 70 GHz LFI bands, respectively.