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.
@article{arxiv.2208.05022,
title = {Cosmology Large Angular Scale Surveyor (CLASS): Pointing Stability and Beam Measurements at 90, 150, and 220 GHz},
author = {Rahul Datta and Michael K. Brewer and Jullianna D. Couto and Joseph R. Eimer and Yunyang Li and Zhilei Xu and John W. Appel and Ricardo Bustos and David T. Chuss and Joseph Cleary and Sumit Dahal and Thomas Essinger-Hileman and Jeffrey Iuliano and Tobias A. Marriage and Carolina Núñez and Matthew A. Petroff and Karwan Rostem and Duncan J. Watts and Edward J. Wollack},
journal= {arXiv preprint arXiv:2208.05022},
year = {2022}
}
Comments
Submitted to Proc. SPIE Astronomical Telescopes and Instrumentation (2022)