The Optical Design Concept for the Atacama Large Aperture Submillimeter Telescope (AtLAST)

TL;DR

The paper presents the optical design concept for the Atacama Large Aperture Submillimeter Telescope (AtLAST), a 50-meter observatory with advanced optical systems to optimize its wide field of view and detector capacity for millimeter/sub-millimeter observations.

Contribution

It introduces a numerically optimized two-mirror Ritchey-Chrétien optical system with a flat folding mirror for AtLAST, enabling flexible instrument positioning and improved optical performance.

Findings

Optical design achieves high throughput and wide field of view.

Design concepts correct for astigmatism and focal surface curvature.

Expected optical performance meets the requirements for sub-millimeter observations.

Abstract

The Atacama Large Aperture Submillimeter Telescope (AtLAST) aims to be the premier next generation large diameter (50-meter) single dish observatory capable of observations across the millimeter/sub-millimeter spectrum, from 30 to 950~GHz. The large primary mirror diameter, the 2-degree field of view and its large 4.7-meter focal surface give AtLAST a high throughput (aperture size times field of view) and grasp (throughput times spectral reach), with the ability to illuminate $>\mathcal{O}(10^7)$ detectors. The optical design concept for AtLAST consists of a numerically optimized two-mirror Ritchey-Chr\'etien system with an additional flat folding mirror, which enables a quick selection among its planned six instrument positions. We present the optical design concept and discuss the expected optical performance of AtLAST. We then present design concepts that can be implemented in the receiver and instrument optics to correct for astigmatism and mitigate the high degree of curvature of the focal surface in order to recover significant fractions of the geometric field of view at sub-millimeter wavelengths.