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

## TL;DR

This paper presents a method to correct bandpass mismatch errors in satellite CMB experiments, significantly reducing leakage bias in B-mode polarization measurements crucial for detecting primordial gravitational waves.

## Contribution

It introduces a template fitting map-maker technique to accurately estimate and subtract intensity-to-polarization leakage caused by bandpass mismatch.

## Key findings

- Reduces bias on B-mode signal by up to 3 orders of magnitude
- Demonstrates effectiveness through simulations
- Improves accuracy of primordial gravitational wave detection

## Abstract

Future Cosmic Microwave Background (CMB) satellite missions aim at using the B-mode polarisation signal to measure the tensor-to-scalar ratio $r$ with a sensitivity $\sigma(r)$ of the order of $\leq 10^{-3}$. Small uncertainties in the characterisation of instrument properties such as the spectral filters can lead to a leakage of the intensity signal to polarisation and can possibly bias any measurement of a primordial signal. In this paper we discuss methods for avoiding and correcting for the intensity to polarisation leakage due to bandpass mismatch among detector sets. We develop a template fitting map-maker to obtain an unbiased estimate of the leakage signal and subtract it out of the total signal. Using simulations we show how such a method can reduce the bias on the observed B-mode signal by up to $3$ orders of magnitude in power.