The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from inflation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70\% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95\% C.L.).
@article{arxiv.1608.08234,
title = {The Cosmology Large Angular Scale Surveyor},
author = {Kathleen Harrington and Tobias Marriage and Aamir Ali and John W. Appel and Charles L. Bennett and Fletcher Boone and Michael Brewer and Manwei Chan and David T. Chuss and Felipe Colazo and Sumit Dahal and Kevin Denis and Rolando Dünner and Joseph Eimer and Thomas Essinger-Hileman and Pedro Fluxa and Mark Halpern and Gene Hilton and Gary F. Hinshaw and Johannes Hubmayr and Jeffery Iuliano and John Karakla and Jeff McMahon and Nathan T. Miller and Samuel H. Moseley and Gonzalo Palma and Lucas Parker and Matthew Petroff and Bastián Pradenas and Karwan Rostem and Marco Sagliocca and Deniz Valle and Duncan Watts and Edward Wollack and Zhilei Xu and Lingzhen Zeng},
journal= {arXiv preprint arXiv:1608.08234},
year = {2016}
}