<i>Planck</i>pre-launch status: Low Frequency Instrument optics

Sandri, M.; Villa, F.; Bersanelli, M.; Burigana, C.; Butler, R. C.; D'Arcangelo, O.; Figini, L.; Gregorio, A.; Lawrence, C. R.; Maino, D.; Mandolesi, N.; Maris, M.; Nesti, R.; Perrotta, F.; Platania, P.; Simonetto, A.; Sozzi, C.; Tauber, J. A.; Valenziano, L.

doi:10.1051/0004-6361/200912891

Cited by 46 publications

(87 citation statements)

References 19 publications

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“…3.1) at the beam peak (Sandri et al 2010). Fortunately, the sky regions covered by the main beam patterns are small enough that we may use the flat-sky approximation when integrating the polarisation response over the main beam.…”

Section: Stokes Parameters and Coordinatesmentioning

confidence: 99%

Planck pre-launch status: Expected LFI polarisation capability

Leahy

Bersanelli

D'Arcangelo

et al. 2010

A&A

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We present a system-level description of the Low Frequency Instrument (LFI) considered as a differencing polarimeter, and evaluate its expected performance. The LFI is one of the two instruments on board the ESA Planck mission to study the cosmic microwave background. It consists of a set of 22 radiometers sensitive to linear polarisation, arranged in orthogonally-oriented pairs connected to 11 feed horns operating at 30, 44 and 70 GHz. In our analysis, the generic Jones and Mueller-matrix formulations for polarimetry are adapted to the special case of the LFI. Laboratory measurements of flight components are combined with optical simulations of the telescope to investigate the values and uncertainties in the system parameters affecting polarisation response. Methods of correcting residual systematic errors are also briefly discussed. The LFI has beam-integrated polarisation efficiency >99% for all detectors, with uncertainties below 0.1%. Indirect assessment of polarisation position angles suggests that uncertainties are generally less than 0.• 5, and this will be checked in flight using observations of the Crab nebula. Leakage of total intensity into the polarisation signal is generally well below the thermal noise level except for bright Galactic emission, where the dominant effect is likely to be spectral-dependent terms due to bandpass mismatch between the two detectors behind each feed, contributing typically 1-3% leakage of foreground total intensity. Comparable leakage from compact features occurs due to beam mismatch, but this averages to <5 × 10 −4 for large-scale emission. An inevitable feature of the LFI design is that the two components of the linear polarisation are recovered from elliptical beams which differ substantially in orientation. This distorts the recovered polarisation and its angular power spectrum, and several methods are being developed to correct the effect, both in the power spectrum and in the sky maps. The LFI will return a high-quality measurement of the CMB polarisation, limited mainly by thermal noise. To meet our aspiration of measuring polarisation at the 1% level, further analysis of flight and ground data is required. We are still researching the most effective techniques for correcting subtle artefacts in polarisation; in particular the correction of bandpass mismatch effects is a formidable challenge, as it requires multi-band analysis to estimate the spectral indices that control the leakage.

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Section: Stokes Parameters and Coordinatesmentioning

confidence: 99%

Planck pre-launch status: Expected LFI polarisation capability

Leahy

Bersanelli

D'Arcangelo

et al. 2010

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“…A detailed description of the Planck telescope and the instrument optics is provided in Tauber et al (2010), Sandri et al (2010) and Maffei et al (2010). The LFI horns are situated in a ring around the HFI, see Fig.…”

Section: Opticsmentioning

confidence: 99%

“…telescope plus instruments; - Mandolesi et al (2010), describing programmatic aspects of the LFI and its development; - Bersanelli et al (2010), describing in detail the design of the LFI; - Mennella et al (2010), describing the test and calibration programme of the LFI at instrument and system levels prior to launch; - , describing the test and calibration of the LFI radiometer chains; - Sandri et al (2010), describing the design and test of the LFI optics; - Leahy et al (2010), describing the polarisation aspects of the LFI, and its expected performance in orbit; - Lamarre et al (2010), describing in detail the on-ground design, manufacture, test and performance of the HFI; - Pajot et al (2010), describing the test and calibration programme of the HFI prior to launch; - Ade et al (2010), describing the design, test and performance of the cryogenic elements of the HFI focal plane; - Holmes et al (2008), describing the design, manufacture and test of the HFI bolometers; - Maffei et al (2010), describing the design and test of the HFI optics; - Rosset et al (2010), describing the polarisation aspects of the HFI.…”

Section: Introductionmentioning

confidence: 99%

Planckpre-launch status: ThePlanckmission

Tauber¹,

Mandolesi

Puget

et al. 2010

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The European Space Agency's Planck satellite, launched on 14 May 2009, is the third-generation space experiment in the field of cosmic microwave background (CMB) research. It will image the anisotropies of the CMB over the whole sky, with unprecedented sensitivity ( ΔT T ∼ 2 × 10 −6 ) and angular resolution (∼5 arcmin). Planck will provide a major source of information relevant to many fundamental cosmological problems and will test current theories of the early evolution of the Universe and the origin of structure. It will also address a wide range of areas of astrophysical research related to the Milky Way as well as external galaxies and clusters of galaxies. The ability of Planck to measure polarization across a wide frequency range (30−350 GHz), with high precision and accuracy, and over the whole sky, will provide unique insight, not only into specific cosmological questions, but also into the properties of the interstellar medium. This paper is part of a series which describes the technical capabilities of the Planck scientific payload. It is based on the knowledge gathered during the on-ground calibration campaigns of the major subsystems, principally its telescope and its two scientific instruments, and of tests at fully integrated satellite level. It represents the best estimate before launch of the technical performance that the satellite and its payload will achieve in flight. In this paper, we summarise the main elements of the payload performance, which is described in detail in the accompanying papers. In addition, we describe the satellite performance elements which are most relevant for science, and provide an overview of the plans for scientific operations and data analysis.

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“…Optical effects arise mainly from Galactic and CMB dipole pick-up caused by primary and secondary mirror spillovers (Tauber et al 2010;Sandri et al 2010). This is relevant especially for polarisation measurements at 30 GHz, where Galactic emissions are stronger.…”

Section: Introductionmentioning

confidence: 99%

Planck2013 results. III. LFI systematic uncertainties

Aghanim

Armitage-Caplan

Arnaud

et al. 2014

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We present the current estimate of instrumental and systematic effect uncertainties for the Planck-Low Frequency Instrument relevant to the first release of the Planck cosmological results. We give an overview of the main effects and of the tools and methods applied to assess residuals in maps and power spectra. We also present an overall budget of known systematic effect uncertainties, which are dominated by sidelobe straylight pick-up and imperfect calibration. However, even these two effects are at least two orders of magnitude weaker than the cosmic microwave background fluctuations as measured in terms of the angular temperature power spectrum. A residual signal above the noise level is present in the multipole range < 20, most notably at 30 GHz, and is probably caused by residual Galactic straylight contamination. Current analysis aims to further reduce the level of spurious signals in the data and to improve the systematic effects modelling, in particular with respect to straylight and calibration uncertainties.

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Planckpre-launch status: Low Frequency Instrument optics

Cited by 46 publications

References 19 publications

Planck pre-launch status: Expected LFI polarisation capability

Planck pre-launch status: Expected LFI polarisation capability

Planckpre-launch status: ThePlanckmission

Planck2013 results. III. LFI systematic uncertainties

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