The Simons Observatory: Design, integration, and testing of the small aperture telescopes

TL;DR

The paper details the design, integration, and testing of small-aperture telescopes for the Simons Observatory, aiming to detect primordial B-modes with high sensitivity and low systematic errors.

Contribution

It presents the detailed design, integration, and testing procedures of the SO small-aperture telescopes, including their optical and cryogenic systems.

Findings

Successful integration and testing of the telescopes at 93 and 145 GHz.

Achieved low systematic errors below the sensitivity threshold.

Validated the telescope design for future CMB observations.

Abstract

The Simons Observatory (SO) is a cosmic microwave background (CMB) survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5,200 m in the Atacama Desert in Chile. The SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes to a sensitivity of $\sigma(r)=0.002$, with quantified systematic errors well below this value. Each SAT is a self-contained cryogenic telescope with a 35$^\circ$ field of view, 42 cm diameter optical aperture, 40 K half-wave plate, 1 K refractive optics, and $<0.1$ K focal plane that holds $>12,000$ TES detectors. We describe the nominal design of the SATs and present details about the integration and testing for one operating at 93 and 145 GHz.