Sroll2

From Planck Legacy Archive Wiki
Jump to: navigation, search

Sroll2[edit]

Disclaimer: the following data sets have been delivered and ingested in the PLA as agreed between ESA and the Sroll2 project reprocessing Planck data. Please note that these products have not been produced by the Planck Collaboration and we do not provide any kind of support for the content of these products. For questions about these products please contact the Sroll2 project directly Jean-Marc Delouis (jean.marc.delouis at ifremer.fr).

Overview and background[edit]

Sroll2 is an improved mapmaking approach with respect to the one used for the Planck High Frequency Instrument 2018 Legacy release. The algorithm SRoll2 better corrects the known instrumental effects that still affected mostly the polarized large-angular-scale data by distorting the signal, and/or leaving residuals observable in null tests. The main systematic effect is the nonlinear response of the onboard analog-to-digital convertors that was cleaned in the Planck HFI Legacy release as an empirical time-varying linear detector chain response which is the first-order effect. The SRoll2 method fits the model parameters for higher-order effects and corrects the full distortion of the signal. The model parameters are fitted using the redundancies in the data by iteratively comparing the data and a model. The polarization efficiency uncertainties and associated errors have also been corrected based on the redundancies in the data and their residual levels characterized with simulations.

SRoll2: an improved mapmaking approach to reduce large-scale systematic effects in the Planck High Frequency Instrument legacy maps (Delouis et al., A&A 609, A38, 2019), A&A

Data Description[edit]

Data set description

The SRoll 2.0 data set is made of 28 FITS files each containing the I, Q and U Stokes parameters of a single frequency, multi-bolometer, full-sky observation in KCMB, as well as its hit count and covariance matrix elements (II, IQ, IU, QQ, QU, UU, in KCMB2). These maps are generated using only the 8 polarised HFI bolometers ("PSB") of each polarised HFI frequency (100 GHz, 143 GHz, 217 GHz and 353 GHz) to obtain the best possible polarised maps. The maps are stored in HEALPix format at Nside=2,048 (50,331,648 pixels per map). They are named and formatted in the same way as the Planck HFI 2018 products (see the Planck Legacy Archive (PLA)):

  • SRoll20 is the data product name and version,
  • SkyMap is the signal type, here all sky components,
  • the detector set, made of the detectors frequency (100, 143, 217, 353), followed by the detectors used in the map (psb for all 8 bolometers, ds1 for the first 4 bolometers, ds2 for the last 4 bolometers)
  • the ring set, either full for all the rings of the mission (240-26050), or halfmission-1 (rings 240-13144), halfmission-2 (rings 13145-26050), or even or odd numbered rings (full-even or full-odd, respectively).


Simulations Description[edit]

The SRoll 2.0 simulations are produced in the same way as Planck HFI 2018 Legacy simulations, described in the Planck Explanatory Supplement. The common features and differences with Planck HFI 2018 simulations are listed here: the simulated sky is the same as Planck 2018 fiducial realisation, the HFI instrument and TOI processing simulation program (stim) is the same one, used with the same parameters and random seeds, the simulated detectors are all (and only) the polarised bolometers, as for the SRoll 2.0 data release (100psb, 143psb, 217psb and 353psb), the global solution and mapmaking algorithm is SRoll2, while the simulations and data processing are done at HEALPix nside=2048, the simulated maps delivered here are smoothed using a cosine pixel window function and downgraded to nside=32, the SRoll 2.0 simulations consists of 500 realisations for 100psb, 143psb and 353psb detsets, and 300 realisations for 217psb.

In the Sroll2 repository the simulations are packaged in three 1.4GB tar files, each file containing all the simulations for a given detector set, respectively all (8) PSB per frequency, detset1 (4 PSB) and detset2 (the other 4 PSB).

In the PLA they are provided as individual files.

Source: http://sroll20.ias.u-psud.fr/sroll20_data.html http://sroll20.ias.u-psud.fr/sroll20_sim.html

Planck Legacy Archive

European Space Agency

(Planck) High Frequency Instrument

Flexible Image Transfer Specification

(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).

Retrieved from ‘https://wiki.cosmos.esa.int/planck-legacy-archive/index.php?title=Sroll2&oldid=14636’