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Planck 2013 results. VIII. HFI photometric calibration and mapmaking

Abstract: This paper describes the methods used to produce photometrically calibrated maps from the Planck High Frequency Instrument (HFI) cleaned, time-ordered information. HFI observes the sky over a broad range of frequencies, from 100 to 857??GHz. To obtain the best calibration accuracy over such a large range, two different photometric calibration schemes have to be used. The 545 and 857?GHz data are calibrated by comparing flux-density measurements of Uranus and Neptune with models of their atmospheric emission. The lower frequencies (below 353??GHz) are calibrated using the solar dipole. A component of this anisotropy is time-variable, owing to the orbital motion of the satellite in the solar system. Photometric calibration is thus tightly linked to mapmaking, which also addresses low-frequency noise removal. By comparing observations taken more than one year apart in the same configuration, we have identified apparent gain variations with time. These variations are induced by non-linearities in the read-out electronics chain. We have developed an effective correction to limit their effect on calibration. We present several methods to estimate the precision of the photometric calibration. We distinguish relative uncertainties (between detectors, or between frequencies) and absolute uncertainties. Absolute uncertainties lie in the range from 0.54% to 10% from 100 to 857??GHz. We describe the pipeline used to produce the maps from the HFI timelines, based on the photometric calibration parameters, and the scheme used to set the zero level of the maps a posteriori. We also discuss the cross-calibration between HFI and the SPIRE instrument on board Herschel. Finally we summarize the basic characteristics of the set of HFI maps included in the 2013 Planck data release.

Otras publicaciones de la misma revista o congreso con autores/as de la Universidad de Cantabria

 Fuente: Astronomy & Astrophysics, 2014, 571, A8

Editorial: EDP Sciences

 Fecha de publicación: 01/11/2014

Nº de páginas: 25

Tipo de publicación: Artículo de Revista

 DOI: 10.1051/0004-6361/201321538

ISSN: 0004-6361,1432-0746

Url de la publicación: https://doi.org/10.1051/0004-6361/201321538

Autoría

ANDRES CURTO MARTIN

JOAQUIN GONZALEZ-NUEVO GONZALEZ

MARCOS LOPEZ-CANIEGO ALCARRIA