Studies of Systematic Uncertainties for Simons Observatory: Optical Effects and Sensitivity Considerations

TL;DR

This paper models optical systematic effects in the Simons Observatory's large aperture telescope, guiding its design and informing future CMB experiments by analyzing errors like pointing, distortions, and polarization.

Contribution

It provides a comprehensive analysis of optical systematic uncertainties for the SO large aperture telescope, aiding design optimization and future experiment planning.

Findings

Optical distortions impact measurement accuracy.

Systematic errors can be mitigated through design adjustments.

Modeling informs calibration and systematic control strategies.

Abstract

The Simons Observatory (SO) is a new experiment that aims to measure the cosmic microwave background (CMB) in temperature and polarization. SO will measure the polarized sky over a large range of microwave frequencies and angular scales using a combination of small ($\sim0.5 \, \rm m$) and large ($\sim 6\, \rm m $) aperture telescopes and will be located in the Atacama Desert in Chile. This work is part of a series of papers studying calibration, sensitivity, and systematic errors for SO. In this paper, we discuss current efforts to model optical systematic effects, how these have been used to guide the design of the SO instrument, and how these studies can be used to inform instrument design of future experiments like CMB-S4. While optical systematics studies are underway for both the small aperture and large aperture telescopes, we limit the focus of this paper to the more mature large aperture telescope design for which our studies include: pointing errors, optical distortions, beam ellipticity, cross-polar response, instrumental polarization rotation and various forms of sidelobe pickup.