Exploring cosmic origins with CORE: mitigation of systematic effects

TL;DR

This paper analyzes systematic effects in the CORE space mission's measurement of CMB polarization, demonstrating that with current techniques, these effects can be mitigated to meet scientific goals.

Contribution

It provides a comprehensive simulation-based assessment of systematic effects and proposes mitigation strategies for the CORE mission's polarization measurements.

Findings

Systematic effects can be mitigated to acceptable levels.

Existing analysis techniques are effective for CORE's systematic control.

Calibration procedures based on Planck are robust for CORE.

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 set-up 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.