The Cosmology Large Angular Scale Surveyor (CLASS) is mapping the polarization of the Cosmic Microwave Background (CMB) at large angular scales (2<ℓ≲200) in search of a primordial gravitational wave B-mode signal down to a tensor-to-scalar ratio of r≈0.01. The same data set will provide a near sample-variance-limited measurement of the optical depth to reionization. Between June 2016 and March 2018, CLASS completed the largest ground-based Q-band CMB survey to date, covering over 31 000~square-degrees (75% of the sky), with an instantaneous array noise-equivalent temperature (NET) sensitivity of 32μ\mboxKcmb\mboxs. We demonstrate that the detector optical loading (1.6\mboxpW) and noise-equivalent power (19\mboxaW\mboxs) match the expected noise model dominated by photon bunching noise. We derive a 13.1±0.3\mboxK/pW calibration to antenna temperature based on Moon observations, which translates to an optical efficiency of 0.48±0.04 and a 27\mboxK system noise temperature. Finally, we report a Tau A flux density of 308±11\mboxJy at 38.4±0.2\mboxGHz, consistent with the WMAP Tau A time-dependent spectral flux density model.
@article{arxiv.1811.08287,
title = {On-sky performance of the CLASS Q-band telescope},
author = {John W. Appel and Zhilei Xu and Ivan L. Padilla and Kathleen Harrington and Bastián Pradenas Marquez and Aamir Ali and Charles L. Bennett and Michael K. Brewer and Ricardo Bustos and Manwei Chan and David T. Chuss and Joseph Cleary and Jullianna Couto and Sumit Dahal and Kevin Denis and Rolando Dünner and Joseph R. Eimer and Thomas Essinger-Hileman and Pedro Fluxa and Dominik Gothe and Gene C. Hilton and Johannes Hubmayr and Jeffrey Iuliano and John Karakla and Tobias A. Marriage and Nathan J. Miller and Carolina Núñez and Lucas Parker and Matthew Petroff and Carl D. Reintsema and Karwan Rostem and Robert W. Stevens and Deniz Augusto Nunes Valle and Bingjie Wang and Duncan J. Watts and Edward J. Wollack and Lingzhen Zeng},
journal= {arXiv preprint arXiv:1811.08287},
year = {2019}
}