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We present a demonstration of the in-flight polarization angle calibrationfor the JAXA/ISAS second strategic large class mission, LiteBIRD, and estimateits impact on the measurement of the tensor-to-scalar ratio parameter, r, usingsimulated data. We generate a set of simulated sky maps with CMB and polarizedforeground emission, and inject instrumental noise and polarization angleoffsets to the 22 (partially overlapping) LiteBIRD frequency channels. Ourin-flight angle calibration relies on nulling the EB cross correlation of thepolarized signal in each channel. This calibration step has been carried out bytwo independent groups with a blind analysis, allowing an accuracy of the orderof a few arc-minutes to be reached on the estimate of the angle offsets. Boththe corrected and uncorrected multi-frequency maps are propagated through theforeground cleaning step, with the goal of computing clean CMB maps. We employtwo component separation algorithms, the Bayesian-Separation of Components andResiduals Estimate Tool (B-SeCRET), and the Needlet Internal Linear Combination(NILC). We find that the recovered CMB maps obtained with algorithms that donot make any assumptions about the foreground properties, such as NILC, areonly mildly affected by the angle miscalibration. However, polarization angleoffsets strongly bias results obtained with the parametric fitting method. Oncethe miscalibration angles are corrected by EB nulling prior to the componentseparation, both component separation algorithms result in an unbiasedestimation of the r parameter. While this work is motivated by the conceptualdesign study for LiteBIRD, its framework can be broadly applied to any CMBpolarization experiment. In particular, the combination of simulation plusblind analysis provides a robust forecast by taking into account not onlydetector sensitivity but also systematic effects.

In-flight polarization angle calibration for LiteBIRD: blind challenge and cosmological implications