Planck 2013 results: IV. Low Frequency Instrument beams and window functions

Jussi Varis, Jussi Tuovinen, M. Sandri (Corresponding Author), Planck Collaboration

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

This paper presents the characterization of the in-flight beams, the beam window functions, and the associated uncertainties for the Planck Low Frequency Instrument (LFI). Knowledge of the beam profiles is necessary for determining the transfer function to go from the observed to the actual sky anisotropy power spectrum. The main beam distortions affect the beam window function, complicating the reconstruction of the anisotropy power spectrum at high multipoles, whereas the sidelobes affect the low and intermediate multipoles. The in-flight assessment of the LFI main beams relies on the measurements performed during Jupiter observations. By stacking the datafrom multiple Jupiter transits, the main beam profiles are measured down to –20 dB at 30 and 44 GHz, and down to –25 dB at 70 GHz. The main beam solid angles are determined to better than 0.2% at each LFI frequency band. The Planck pre-launch optical model is conveniently tuned to characterize the main beams independently of any noise effects. This approach provides an optical model whose beams fully reproduce the measurements in the main beam region, but also allows a description of the beams at power levels lower than can be achieved by the Jupiter measurements themselves. The agreement between the simulated beams and the measured beams is better than 1% at each LFI frequency band. The simulated beams are used for the computation of the window functions for the effective beams. The error budget for the window functions is estimated from both main beam and sidelobe contributions, and accounts for the radiometer bandshapes. The total uncertainties in the effective beam window functions are: 2% and 1.2% at 30 and 44 GHz, respectively (at ℓ ≈ 600), and 0.7% at 70 GHz (at ℓ ≈ 1000).
Original languageEnglish
Article numberA4
Number of pages22
JournalAstronomy and Astrophysics
Volume571
DOIs
Publication statusPublished - 2014
MoE publication typeA1 Journal article-refereed

Fingerprint

Jupiter
low frequencies
anisotropy
flight
transfer function
stacking
radiometer
Jupiter (planet)
sidelobes
multipoles
power spectra
transit
profiles
radiometers
budgets
transfer functions
sky
budget
noise effect

Keywords

  • data analysis
  • cosmic background radiation
  • telescopes

Cite this

Varis, Jussi ; Tuovinen, Jussi ; Sandri, M. ; Planck Collaboration. / Planck 2013 results : IV. Low Frequency Instrument beams and window functions. In: Astronomy and Astrophysics. 2014 ; Vol. 571.
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Planck 2013 results : IV. Low Frequency Instrument beams and window functions. / Varis, Jussi; Tuovinen, Jussi; Sandri, M. (Corresponding Author); Planck Collaboration.

In: Astronomy and Astrophysics, Vol. 571, A4, 2014.

Research output: Contribution to journalArticleScientificpeer-review

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