CMB polarization analysis on circular scans

TL;DR

This paper introduces a method to directly estimate CMB temperature and polarization spectra from circular scan data using linear systems, improving noise handling without full map reconstruction.

Contribution

It presents a novel linear system approach to extract harmonic spectra directly from time-ordered data in circular scans, bypassing traditional map-making.

Findings

Direct estimation of T, E, B spectra from data streams.

Effective down-weighting of contaminated modes.

Potential for improved analysis of future CMB data.

Abstract

Most cosmic microwave background experiments observe the sky along circular or near-circular scans on the celestial sphere. For such experiments, we show that simple linear systems connect the Fourier spectra of temperature and polarization time-ordered data to the harmonic spectra of T, E and B on the sphere. We show how this can be used to estimate those spectra directly from data streams. In addition, the inversion of the linear system that connects Fourier spectra to angular power spectra offers a natural way to down-weight those modes of observation most contaminated by low-frequency noise, ground pickup, or fluctuations of atmospheric emission on large angular scale. This can be of interest for the analysis of future CMB data sets, as an alternative or in complement to other approaches that involve map-making as a first analysis step.