The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array observing the Cosmic Microwave Background (CMB) at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the CMB polarization on the largest angular scales to constrain the inflationary tensor-to-scalar ratio and the optical depth due to reionization. To achieve the long time-scale stability necessary for this measurement from the ground, CLASS utilizes a front-end, variable-delay polarization modulator on each telescope. Here we report on the improvements in stability afforded by front-end modulation using data across all four CLASS frequencies. Across one month of modulated linear polarization data in 2021, CLASS achieved median knee frequencies of 9.1, 29.1, 20.4, and 36.4 mHz for the 40, 90, 150, and 220 GHz observing bands. The knee frequencies are approximately an order of magnitude lower than achieved via CLASS pair-differencing orthogonal detector pairs without modulation.
@article{arxiv.2208.04996,
title = {Long-Timescale Stability in CMB Observations at Multiple Frequencies using Front-End Polarization Modulation},
author = {Joseph Cleary and Rahul Datta and John W. Appel and Charles L. Bennett and David T. Chuss and Jullianna Denes Couto and Sumit Dahal and Francisco Espinoza and Thomas Essinger-Hileman and Kathleen Harrington and Jeffrey Iuliano and Yunyang Li and Tobias A. Marriage and Carolina Nunez and Matthew A. Petroff and Rodrigo A. Reeves and Rui Shi and Duncan J. Watts and Edward J. Wollack and Zhilei Xu},
journal= {arXiv preprint arXiv:2208.04996},
year = {2022}
}
Comments
Submitted to SPIE Astronomical Telescopes + Instrumentation 2022 Conference (AS22)