The Simons Observatory: Modeling Optical Systematics in the Large Aperture Telescope

TL;DR

This paper details comprehensive optical system modeling for the Simons Observatory's Large Aperture Telescope, assessing design choices and systematic effects to optimize performance and mitigate potential issues.

Contribution

It introduces detailed geometrical and physical optics simulations that evaluate the telescope's design, focusing on optical performance and systematic error mitigation.

Findings

Optimized reflector and cold optics design.

Identified geometries reducing detector loading.

Analyzed beam sidelobes from panel gap diffraction.

Abstract

We present geometrical and physical optics simulation results for the Simons Observatory Large Aperture Telescope. This work was developed as part of the general design process for the telescope; allowing us to evaluate the impact of various design choices on performance metrics and potential systematic effects. The primary goal of the simulations was to evaluate the final design of the reflectors and the cold optics which are now being built. We describe non-sequential ray tracing used to inform the design of the cold optics, including absorbers internal to each optics tube. We discuss ray tracing simulations of the telescope structure that allow us to determine geometries that minimize detector loading and mitigate spurious near-field effects that have not been resolved by the internal baffling. We also describe physical optics simulations, performed over a range of frequencies and field locations, that produce estimates of monochromatic far field beam patterns which in turn are used to gauge general optical performance. Finally, we describe simulations that shed light on beam sidelobes from panel gap diffraction.