Cosmology Large Angular Scale Surveyor (CLASS): Pointing Stability and Beam Measurements at 90, 150, and 220 GHz

Rahul Datta; Michael K. Brewer; Jullianna D. Couto; Joseph R. Eimer; Yunyang Li; Zhilei Xu; John W. Appel; Ricardo Bustos; David T. Chuss; Joseph Cleary; Sumit Dahal; Thomas Essinger-Hileman; Jeffrey Iuliano; Tobias A. Marriage; Carolina Núñez; Matthew A. Petroff; Karwan Rostem; Duncan J. Watts; Edward J. Wollack

arXiv · 2208.05022

Cosmology Large Angular Scale Surveyor (CLASS): Pointing Stability and Beam Measurements at 90, 150, and 220 GHz

Rahul Datta·Michael K. Brewer·Jullianna D. Couto·Joseph R. Eimer·Yunyang Li·Zhilei Xu·John W. Appel·Ricardo Bustos·David T. Chuss·Joseph Cleary·Sumit Dahal·Thomas Essinger-Hileman·Jeffrey Iuliano·Tobias A. Marriage·Carolina Núñez·Matthew A. Petroff·Karwan Rostem·Duncan J. Watts·Edward J. Wollack

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Abstract

The Cosmology Large Angular Scale Surveyor (CLASS) telescope array surveys 75% of the sky from the Atacama desert in Chile at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the largest-angular-scale CMB polarization with the aim of constraining the tensor-to-scalar ratio, measuring the optical depth to reionization to near the cosmic variance limit, and more. The CLASS Q-band (40 GHz), W-band (90 GHz), and dichroic high frequency (150/220 GHz) telescopes have been observing since June 2016, May 2018, and September 2019, respectively. On-sky optical characterization of the 40 GHz instrument has been published. Here, we present preliminary on-sky measurements of the beams at 90, 150, and 220 GHz, and pointing stability of the 90 and 150/220 GHz telescopes. The average 90, 150, and 220 GHz beams measured from dedicated observations of Jupiter have full width at half maximum (FWHM) of 0.615+/-0.019 deg, 0.378+/-0.005 deg, and 0.266+/-0.008 deg, respectively. Telescope pointing variations are within a few percent of the beam FWHM.

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Rahul Datta, Michael K. Brewer, Jullianna D. Couto, Joseph R. Eimer, Yunyang Li, Zhilei Xu, John W. Appel, Ricardo Bustos, David T. Chuss, Joseph Cleary, Sumit Dahal, Thomas Essinger-Hileman, Jeffrey Iuliano, Tobias A. Marriage, Carolina Núñez, Matthew A. Petroff, Karwan Rostem, Duncan J. Watts, Edward J. Wollack. 2022-08-09. Cosmology Large Angular Scale Surveyor (CLASS): Pointing Stability and Beam Measurements at 90, 150, and 220 GHz. https://arxiv.org/abs/2208.05022

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