Beam Window Functions

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Beam window functions have been computed with the Febecop Pipeline (as described there), and the QuickPol pipeline (see Hivon et al, 2017[1], and the Planck 2016 Likelihood paper[2]).

The beam window function relates (over the full or masked sky) the angular power spectrum measured (in the absence of noise) on a map produced by a set of detectors CXXmap(ℓ), to the true underlying sky angular power spectrum CXXsky(ℓ), assumed to have isotropic statistical properties, as is the case for the CMB.

QuickPol effective beam window products[edit]

The effective beam products are defined for each multipole 0 ≤ ℓ ≤ ℓmax = 4000.

They are available in three forms:

Temperature beam window functions for polarized and unpolarized detectors (HFI PSB and SWBs)[edit]

The temperature beam window function bT(ℓ), is such that

[math]C^{TT}_\text{map}(\ell)\, = \, b_{T}^2(\ell) \, w_\text{pix}^2(\ell) \, C^{TT}_\text{sky}(\ell)[/math],

where wpix is the pixel window function, parameterized by the HEALPix resolution parameter Nside (=2048 for Planck HFI maps). Their availability is described in the Availability section.

Temperature and polarized beam window functions for polarized detectors (HFI PSBs)[edit]

The temperature and polarization beam window functions bT(ℓ), bE(ℓ), and bT(ℓ) are such that

[math]C^{XX}_\text{map}(\ell)\, = \, b_{X}^2(\ell) \, w_\text{pix}^2(\ell) \, C^{XX}_\text{sky}(\ell)[/math]

for X = T, E, or B, and where wpix is defined above. Their availability is described in the Availability section.

  • These polarized and unpolarized effective beam window functions are provided in FITS format files compatible with HEALPix tools for map synthesis (such as synfast or syn_alm_cxx) or map smoothing (such as smoothing or smoothing_cxx), as well as with map analysis tools such as PolSpice.

Beam matrices for polarized detectors[edit]

The beam matrices WXY,X'Y'(ℓ) are such that

[math]C^{XY}_\text{map}(\ell) \, = \, \sum_{X',Y'} W_{XY,X'Y'}(\ell) \, w_\text{pix}^2(\ell) \, C^{X'Y'}_\text{sky}(\ell)[/math]

for X,Y,X',Y' = T, E, or B, and where wpix is defined above.

The non-diagonal terms of the matrix (XYX'Y'), not present in the usual beam window function defined in the previous section, describe the power spectra cross-talk induced by the non-circularity of the scanning beam and the inter-detector beam mismatch; they are important for the high-ℓ cosmological analysis of the CMB polarization, which is done mostly at 100, 143, and 217GHz for HFI.

  • They are provided in FITS files, containing four extensions each:
  1. the first one, named "TT", contains the nine fields: "TT_2_TT", "TT_2_EE", "TT_2_BB", "TT_2_TE", "TT_2_TB", "TT_2_EB", "TT_2_ET", "TT_2_BT", "TT_2_BE", describing the ℓ-dependent leakage template of TT into TT, EE, BB, ..., respectively, with "TT_2_TT" being the usual WTT(ℓ) = bT2(ℓ), with bT(ℓ=0)=1;
  2. the second extension, named "EE", contains the nine fields "EE_2_TT", "EE_2_EE", "EE_2_BB", ... for leakage of EE into TT, EE, BB, ..., with "EE_2_EE" being the usual WEE(ℓ) = bE2(ℓ);
  3. the third extension is "BB", with "BB_2_TT", ..., where "BB_2_BB" is the usual WBB(ℓ) = bB2(ℓ);
  4. the fourth extension is "TE" with "TE_2_TT", ... .
Beware that there is no extension 5 or 6, corresponding to TB and EB, since these terms are unlikely to be major sources of contamination for the other spectra.
The measured C*(ℓ) are then related to the sky ones C(ℓ) via (ignoring the pixel window function wpix2(ℓ)):
CTT*(ℓ) = CTT(ℓ) TT_2_TT(ℓ) + CEE(ℓ) EE_2_TT(ℓ) + CBB(ℓ) BB_2_TT(ℓ) + CTE(ℓ) TE_2_TT(ℓ);
CEE*(ℓ) = CTT(ℓ) TT_2_EE(ℓ) + CEE(ℓ) EE_2_EE(ℓ) + CBB(ℓ) BB_2_EE(ℓ) + CTE(ℓ) TE_2_EE(ℓ);
CBB*(ℓ) = CTT(ℓ) TT_2_BB(ℓ) + CEE(ℓ) EE_2_BB(ℓ) + CBB(ℓ) BB_2_BB(ℓ) + CTE(ℓ) TE_2_BB(ℓ);
CTE*(ℓ) = CTT(ℓ) TT_2_TE(ℓ) + CEE(ℓ) EE_2_TE(ℓ) + CBB(ℓ) BB_2_TE(ℓ) + CTE(ℓ) TE_2_TE(ℓ);
CET*(ℓ) = CTT(ℓ) TT_2_ET(ℓ) + CEE(ℓ) EE_2_ET(ℓ) + CBB(ℓ) BB_2_ET(ℓ) + CTE(ℓ) TE_2_ET(ℓ).
  • Their availability is described in the Availability section.


The beam window function products are all contained in the same directory BeamWF_HFI_R3.00, shipped in the tar-ball HFI_RIMO_BEAMS_R3.01.tar.gz available in the PLA.

Note: the tar-ball HFI_RIMO_BEAMS_R3.00.tar.gz has been replaced with HFI_RIMO_BEAMS_R3.01.tar.gz in the PLA because the 857 GHz beam window functions were missing.

They are systematically provided for the (co-)analysis of:

  • the full mission;
  • the half-mission1 / half-mission2; and
  • even-rings / odd-rings.

HFI frequency maps described there.

These products are identified by a string of the form map1xmap2, where "map1" and "map2" each take the form "freqtype", with

  • "freq" being the map frequency in GHz selected from "100", "143", "217", "353" (PSB+SWB), "353p" (PSB only), "545", "857" (with "freq1" ≤ "freq2") and
  • "type" being either empty (full mission map), "hm1" or "hm2" (for 1st and 2nd half-missions), or "even" or "odd" (for maps made of even or odd rings).

Examples of "map1" "x" "map2: values:

  • 143x217 (for full mission maps);
  • 100hm1x353phm2 (correlation of 100GHz 1st Half mission map, with 353GHz PSB only 2nd Half mission map);
  • 217oddx217odd (auto-correlation of 217GHz odd-rings map), ... .

T or TEB window functions[edit]

  • T only: 100 to 857GHz for full-sky maps:
  • TEB: 100 to 353GHz for full-sky maps:

Polarized beam matrices[edit]

  • 100, 143, 217, and 353 GHz, full-sky maps:
  • 100, 143, and 217GHz, Plik-like masks:
    • valid for analysis done on maps masked with the Plik masks described ?? ;
    • Wl_R3.00_plikmask_map1xmap2.fits .

FITS parsing[edit]

These FITS files can be read in IDL and python, as follows.

  • IDL:
fits_info, FITSfile,extname=extname ; print list of extensions found in FITSfile, and store their names in extname
data=mrdfits(FITSfile, 10, header)  ; read extension #10 (data and header)
data=mrdfits(FITSfile, 'ABC', header)  ; read extension having EXTNAME='ABC' (data and header)
print,header  ; print header
print,tag_names(data)  ; print column names
plot,data.(0)  ; plot 1st column of binary table
Note: this requires recent versions of fits_info, mrdfits, and their supporting routines, all available at .
  • python2:
import as pf
import pylab # only to produce plots # print list of extensions found in FITSfile
data, header = pf.getdata(FITSfile, 10, header=True) # read extension #10 (data and header)
data, header = pf.getdata(FITSfile, 'ABC', header=True) # read extension having EXTNAME='ABC' (data and header)
print header # print header
print data.names # print column names
pylab.plot( data.field(0).flatten() ) # plot 1st column of binary table
Note: replaces the older pyfits.
  • python3:
same as python2, replacing   print x   with   print (x)

Other Releases: 2020-NPIPE beam window function[edit]

2020 Release beam window function (NPIPE)

Each Planck detector has a different effective beam. The effective beams result from the optical system, sample integration and data processing like bolometric transfer function deconvolution. The beams combine with the anisotropic Planck scan strategy and detector weights to produce frequency and data split-dependent beam transfer functions.

QuickPol[3] is an algorithm that allows combining the measured effective beams with the scan strategy to evaluate symmetrized beam window functions for auto and cross spectra.

We provide the QuickPol transfer functions for all frequency combinations, as well as AxA, AxB and BxB split map spectra. They are included in the auxiliary data file: PLANCK_RIMO_TF_R4.00.tar.gz as a subdirectory beam_window_functions.

Additionally, the large scale polarization transfer function for one particular choice of sky cut and pixel weighting is available as a subdirectory, large_scale_transfer_functions, of the same package.


  1. Hivon E., Mottet, S. & Ponthieu N., 2017 QuickPol: Fast calculation of effective beam matrices for CMB polarization A&A 598, A25
  2. Planck collaboration, 2018, Planck 2016 results. V. Legacy Power Spectra and Likelihoods
  3. E. Hivon, S. Mottet and N. Ponthieu: QuickPol: Fast calculation of effective beam matrices for CMB polarization, A&A 643, A42 (2020) arXiv:1608.08833.

--Ehivon (talk) 15:30, 16 February 2018 (CET)
--Ehivon (talk) 18:05, 19 February 2018 (CET)
--Ehivon (talk) 18:55, 29 March 2018 (CEST)

Cosmic Microwave background

(Planck) High Frequency Instrument

(Hierarchical Equal Area isoLatitude Pixelation of a sphere, <ref name="Template:Gorski2005">HEALPix: A Framework for High-Resolution Discretization and Fast Analysis of Data Distributed on the Sphere, K. M. Górski, E. Hivon, A. J. Banday, B. D. Wandelt, F. K. Hansen, M. Reinecke, M. Bartelmann, ApJ, 622, 759-771, (2005).

Flexible Image Transfer Specification

reduced IMO

Planck Legacy Archive