Exploring cosmic origins with CORE: Mitigation of systematic effects

Abstract

We present an analysis of the main systematic effects that could impact the measurement of CMB polarization with the proposed CORE space mission. We employ timeline-to-map simulations to verify that the CORE instrumental setup and scanning strategy allow us to measure sky polarization to a level of accuracy adequate to the mission science goals. We also show how the CORE observations can be processed to mitigate the level of contamination by potentially worrying systematics, including intensity-to-polarization leakage due to bandpass mismatch, asymmetric main beams, pointing errors and correlated noise. We use analysis techniques that are well validated on data from current missions such as Planck to demonstrate how the residual contamination of the measurements by these effects can be brought to a level low enough not to hamper the scientific capability of the mission, nor significantly increase the overall error budget. We also present a prototype of the CORE photometric calibration pipeline, based on that used for Planck, and discuss its robustness to systematics, showing how CORE can achieve its calibration requirements. While a fine-grained assessment of the impact of systematics requires a level of knowledge of the system that can only be achieved in a future study phase, the analysis presented here strongly suggests that the main areas of concern for the CORE mission can be addressed using existing knowledge, techniques and algorithms.

Exploring cosmic origins with CORE: Effects of observer peculiar motion

“…It was shown in Ref. [65,72] that the kernels can be well approximated by Bessel functions as follows: 6) and n ≥ 1 (where n is the difference in multipole between a pair of coupled multipoles, namely and ± n ). It is also assumed that β 1, although the formula above can be generalised to large β [65,72].…”

“…We refer the reader to the CORE proposal [1] and to other dedicated ECO papers for more details, in particular the mission requirements and design paper [2] and the instrument paper [3], which provide a comprehensive discussion of the key parameters of CORE adopted in this work. We also refer the reader to the paper on extragalactic sources [4] for an investigation of their contribution to the cosmic infrared background (CIB), which is one of the key topics addressed in the present paper, as well as the papers on B-mode component separation [5] for a stronger focus on polarization, and mitigation of systematic effects [6] for further discussion of potential residuals included in some analyses presented in this work. Throughout this paper we use the CORE specifications summarised in Table 1.…”

Bandpass mismatch error for satellite CMB experiments II: correcting for the spurious signal

“…Here, we investigate the effectiveness of an alternative approach to mitigate, in the map-making step, the leakage of signal from intensity to polarization due to bandpass mismatch among a set of detectors when no HWP is used in the observation. We extend the preliminary work done in the context of the CORE systematic effects study outlined in section 6 of [22]. The study of whether it is possible to correct the impact of HWP imperfections is beyond the scope of this paper.…”

Perspectives for Cosmological Reionization From Future CMB and Radio Projects

“…The entire sky will be observed repeatedly during 4 years of continuous scanning, with a combination of three rotations of the spacecraft over different time scales so that each sky pixel is observed repeatedly with many different beam orientations, providing polarization measurements at many different angles. Another key requirement is the measurement accuracy: all systematic effects, further corrected also (Natoli et al, 2018) in combination with data processing, will be controlled so that no more than approximately 10 −4 of the intensity leaks into polarization maps, and that no more than about 1% of E-type polarization leaks into B-type modes.…”