Destriping CMB temperature and polarization maps

Kurki-Suonio, H.; Keihänen, E.; Keskitalo, R.; Poutanen, T.; Sirvio, A.-S.; Maino, D.; Burigana, C.

doi:10.1051/0004-6361/200912361

Cited by 47 publications

(54 citation statements)

References 35 publications

(49 reference statements)

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“…At 30 GHz the 1/ f noise is higher than measured on the ground, with a knee frequency of about 100 mHz. Residual fluctuations in the timestreams, however, are effectively removed during map-making, as expected from several pre-launch simulation studies (Kurki-Suonio et al 2009;Poutanen et al 2004;Keihänen et al 2004). We have shown that the noise increase due to the 1/ f component is a few percent at 30 and 44 GHz, and only 0.2% at 70 GHz.…”

Section: Discussionsupporting

confidence: 74%

Planckearly results. III. First assessment of the Low Frequency Instrument in-flight performance

Mennella

Bersanelli

Butler

et al. 2011

A&A

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114

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The scientific performance of the Planck Low Frequency Instrument (LFI) after one year of in-orbit operation is presented. We describe the main optical parameters and discuss photometric calibration, white noise sensitivity, and noise properties. A preliminary evaluation of the impact of the main systematic effects is presented. For each of the performance parameters, we outline the methods used to obtain them from the flight data and provide a comparison with pre-launch ground assessments, which are essentially confirmed in flight.

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Section: Discussionsupporting

confidence: 74%

Planckearly results. III. First assessment of the Low Frequency Instrument in-flight performance

Mennella

Bersanelli

Butler

et al. 2011

A&A

Self Cite

114

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“…For Planck's actual scan strategy, scan circle crossings at substantial angles occur over about ±20 • around the poles, so that a much longer run of the circle is involved in constraining the offsets, giving higher signal to noise, and also reducing the sensitivity to monopole-dipole degeneracy. The actual determination of the offsets will be made in the course of iterative destriping, for instance using the madam algorithm (Keihänen et al 2005;Keihänen et al 2010;Ashdown et al 2007;Kurki-Suonio et al 2009). …”

Section: Zero Levels and Destripingmentioning

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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“…The first term on the rhs is the binned white noise contribution (a diagonal or block-diagonal matrix for temperature-only and polarized cases respectively) and the second term describes the pixel-pixel correlations due to errors in solving for the baselines, i.e., the difference between the solved and actual baselines (Kurki-Suonio et al 2009). When making a map using destriping, one can use high resolution to solve for baselines and still bin the map at low resolution.…”

Section: Destriped Map Covariancementioning

confidence: 99%

Residual noise covariance forPlancklow-resolution data analysis

Keskitalo

Ashdown

Cabella

et al. 2010

A&A

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Aims. We develop and validate tools for estimating residual noise covariance in Planck frequency maps, we also quantify signal error effects and compare different techniques to produce low-resolution maps. Methods. We derived analytical estimates of covariance of the residual noise contained in low-resolution maps produced using a number of mapmaking approaches. We tested these analytical predictions using both Monte Carlo simulations and by applying them to angular power spectrum estimation. We used simulations to quantify the level of signal errors incurred in the different resolution downgrading schemes considered in this work. Results. We find excellent agreement between the optimal residual noise covariance matrices and Monte Carlo noise maps. For destriping mapmakers, the extent of agreement is dictated by the knee frequency of the correlated noise component and the chosen baseline offset length. Signal striping is shown to be insignificant when properly dealt with. In map resolution downgrading, we find that a carefully selected window function is required to reduce aliasing to the subpercent level at multipoles, > 2N side , where N side is the HEALPix resolution parameter. We show that, for a polarization measurement, reliable characterization of the residual noise is required to draw reliable constraints on large-scale anisotropy.Conclusions. Methods presented and tested in this paper allow for production of low-resolution maps with both controlled sky signal error level and a reliable estimate of covariance of the residual noise. We have also presented a method for smoothing the residual noise covariance matrices to describe the noise correlations in smoothed, bandwidth-limited maps.

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Destriping CMB temperature and polarization maps

Cited by 47 publications

References 35 publications

Planckearly results. III. First assessment of the Low Frequency Instrument in-flight performance

Planckearly results. III. First assessment of the Low Frequency Instrument in-flight performance

Planck pre-launch status: Expected LFI polarisation capability

Residual noise covariance forPlancklow-resolution data analysis

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