Four-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: On-sky Receiver Performance at 40, 90, 150, and 220 GHz Frequency Bands

Abstract

The Cosmology Large Angular Scale Surveyor (CLASS) observes the polarized cosmic microwave background (CMB) over the angular scales of 1${}^{\circ }\lesssim \theta \le$ 90${}^{\circ }$ 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 June 2016, May 2018, and September 2019, 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 ${\mu \mathrm{K}}_{\mathrm{cmb}}\sqrt{\mathrm{s}}$ 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.

13 pages, 3 figures, published in ApJ

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• The Atacama Cosmology Telescope: Map-Based Noise Simulations for DR6
• Calibration of Transition-edge Sensor (TES) Bolometer Arrays with Application to CLASS
• Polarized Synchrotron Foreground Assessment for CMB Experiments
• Testing CMB Anomalies in E-mode Polarization with Current and Future Data
• Detectability of the cross-correlation between CMB lensing and stochastic GW background from compact object mergers
• Large and small field inflation from hyperbolic sigma models
• Probing the Early History of Cosmic Reionization by Future Cosmic Microwave Background Experiments
• Constraints on the Optical Depth to Reionization from Balloon-Borne CMB Measurements
• Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance
• Cosmic Birefringence from CP-Violating Axion Interactions
• PROTOCALC, A W-band polarized calibrator for CMB Telescopes: application to Simons Observatory and CLASS
• On-sky performance of new 90 GHz detectors for the Cosmology Large Angular Scale Surveyor (CLASS)
• Microwave Observations of Venus with CLASS
• Scaling behavior of observables as a model characteristic in multifield inflation
• CMB lensing from early-formed dark matter halos
• High-Efficiency and Low-Noise Detectors for the Upgraded CLASS 90 GHz Focal Plane
• Bias in the tensor-to-scalar ratio from self-interacting dark radiation
• Optimal map-making with singularities