Four-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: On-sky Receiver Performance at 40, 90, 150, and 220 GHz Frequency Bands
Sumit Dahal, John W. Appel, Rahul Datta, Michael K. Brewer, Aamir Ali, C. L. Bennett, Ricardo Bustos, Manwei Chan, David T. Chuss, Joseph Cleary, Jullianna Denes Couto, Kevin L. Denis, Rolando Dünner, Joseph R. Eimer, Francisco Espinoza, Thomas Essinger-Hileman, Joseph E. Golec, Kathleen Harrington, Kyle Helson, Jeffrey Iuliano, John Karakla, Yunyang Li, Tobias A. Marriage, Jeffrey J. McMahon, N. J. Miller, Sasha Novack, Carolina Núñez, Keisuke Osumi, Ivan L. Padilla, Gonzalo A. Palma, Lucas Parker, Matthew A. Petroff, R. Reeves, Gary Rhoades, Karwan Rostem, Deniz A. N. Valle, Duncan J. Watts, J. L. Weiland, Edward J. Wollack, Zhilei Xu
Abstract
Abstract The Cosmology Large Angular Scale Surveyor (CLASS) observes the polarized cosmic microwave background (CMB) over the angular scales of 1° ≲ θ ≤ 90° with the aim of characterizing primordial gravitational waves and cosmic reionization. We report on the on-sky performance of the CLASS Q -band (40 GHz), W -band (90 GHz), and dichroic G -band (150/220 GHz) receivers that have been operational at the CLASS site in the Atacama desert since 2016 June, 2018 May, and 2019 September, respectively. We show that the noise-equivalent power measured by the detectors matches the expected noise model based on on-sky optical loading and lab-measured detector parameters. Using Moon, Venus, and Jupiter observations, we obtain power to antenna temperature calibrations and optical efficiencies for the telescopes. From the CMB survey data, we compute instantaneous array noise-equivalent-temperature sensitivities of 22, 19, 23, and 71 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>μ</mml:mi> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">K</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>cmb</mml:mi> </mml:mrow> </mml:msub> <mml:msqrt> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:msqrt> </mml:math> for the 40, 90, 150, and 220 GHz frequency bands, respectively. These noise temperatures refer to white noise amplitudes, which contribute to sky maps at all angular scales. Future papers will assess additional noise sources impacting larger angular scales.