Abstract
This paper describes an improved map making 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. This paper demonstrates the effectiveness of the method using end-to-end simulations, and provides a measure of the systematic effect residuals that now fall well below the detector noise level. Finally, this paper describes and characterizes the resulting SRoll2 frequency maps using the associated simulations that are released to the community.
Highlights
The development of the SRoll global solution has been initiated within the Planck High Frequency Instrument (HFI) Consortium, attempting to reduce the systematic effects that impact the large-scale polarization of the HFI frequency maps at 100, 143, 217, and 353 GHz
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 timevarying linear detector chain response which is the first-order effect
This paper presents the second generation of this algorithm, called SRoll2, developed beyond the Planck Collaboration one, to further reduce the main residual systematic effects left in the HFI2018 maps, firstly the second-order correction of the analog-to-digital convertor nonlinearity (ADCNL); secondly the temperature-to-polarization leakage from the polarization efficiency and imperfect orientation knowledge of the bolometer;thirdly the temperature-to-polarization leakage from bandpass mismatch of foregrounds and associated foreground modeling; fourthly the transfer function associated with very long time constants
Summary
The development of the SRoll global solution has been initiated within the Planck High Frequency Instrument (HFI) Consortium, attempting to reduce the systematic effects that impact the large-scale polarization of the HFI frequency maps at 100, 143, 217, and 353 GHz. The basically unchanged algorithm with marginal improvements, described in Planck Collaboration III (2019, hereafter L03 paper), was used for building the 2018 Legacy HFI frequency maps. Those maps are referred to in this paper as HFI2018 maps. This paper presents the second generation of this algorithm, called SRoll, developed beyond the Planck Collaboration one, to further reduce the main residual systematic effects left in the HFI2018 maps, firstly the second-order correction of the analog-to-digital convertor nonlinearity (ADCNL); secondly the temperature-to-polarization leakage from the polarization efficiency and imperfect orientation knowledge of the bolometer;thirdly the temperature-to-polarization leakage from bandpass mismatch of foregrounds and associated foreground modeling; fourthly the transfer function associated with very long time constants. This paper is organized as follows: Sect. 2 presents the SRoll algorithm; Sect. 3 presents the resulting SRoll maps; Sect. 4 presents the characterization of those maps and estimation of the systematic effect residuals
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