Abstract
This paper provides an overview of the Low Frequency Instrument (LFI) programme within the ESA Planck mission. The LFI instrument has been developed to produce high precision maps of the microwave sky at frequencies in the range 27-77 GHz, below the peak of the cosmic microwave background (CMB) radiation spectrum. The scientific goals are described, ranging from fundamental cosmology to Galactic and extragalactic astrophysics. The instrument design and development are outlined, together with the model philosophy and testing strategy. The instrument is presented in the context of the Planck mission. The LFI approach to ground and inflight calibration is described. We also describe the LFI ground segment. We present the results of a number of tests demonstrating the capability of the LFI data processing centre (DPC) to properly reduce and analyse LFI flight data, from telemetry information to calibrated and cleaned time ordered data, sky maps at each frequency (in temperature and polarization), component emission maps (CMB and diffuse foregrounds), catalogs for various classes of sources (the Early Release Compact Source Catalogue and the Final Compact Source Catalogue). The organization of the LFI consortium is briefly presented as well as the role of the core team in data analysis and scientific exploitation. All tests carried out on the LFI flight model demonstrate the excellent performance of the instrument and its various subunits. The data analysis pipeline has been tested and its main steps verified. In the first three months after launch, the commissioning, calibration, performance, and verification phases will be completed, after which Planck will begin its operational life, in which LFI will have an integral part.
Highlights
In 1992, the COsmic Background Explorer (COBE) team announced the discovery of intrinsic temperature fluctuations in the cosmic microwave background radiation (CMB; see Appendix A for a list of the acronyms appearing in this paper) on angular scales greater than 7◦ and at a level of a few tens of μK (Smoot et al 1992)
Planck is equipped with a 1.5-m effective aperture telescope with two actively-cooled instruments that will scan the sky in nine frequency channels from 30 GHz to 857 GHz: the Low Frequency Instrument (LFI) operating at 20 K with pseudo-correlation radiometers, and the High Frequency Instrument (HFI; Lamarre et al 2010) with bolometers operating at 100 mK
We assumed that the 70 GHz channels and the 100 GHz and 143 GHz are the representative channels for LFI and HFI
Summary
In 1992, the COsmic Background Explorer (COBE) team announced the discovery of intrinsic temperature fluctuations in the cosmic microwave background radiation (CMB; see Appendix A for a list of the acronyms appearing in this paper) on angular scales greater than 7◦ and at a level of a few tens of μK (Smoot et al 1992). Planck is equipped with a 1.5-m effective aperture telescope with two actively-cooled instruments that will scan the sky in nine frequency channels from 30 GHz to 857 GHz: the Low Frequency Instrument (LFI) operating at 20 K with pseudo-correlation radiometers, and the High Frequency Instrument (HFI; Lamarre et al 2010) with bolometers operating at 100 mK. While HFI is more sensitive and should achieve higher angular resolution, the combination of the two instruments is required to accurately subtract Galactic emission, thereby allowing a reconstruction of the primordial CMB anisotropies to high precision. LFI was to include seventeen 100 GHz horns with 34 high sensitivity radiometers This system, which could have granted redundancy and cross-calibration with HFI as well as a cross-check of systematics, was not implemented. Angular resolution [arcmin] δT per 30 pixel [μK] δT/T per pixel [μK/K] Number of radiometers (or feeds) Effective bandwidth [GHz] System noise temperature [K] √ White noise per channel [μK · s] Systematic effects [μK]
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