Overview of the Optical Design of the CMB-S4 Large Aperture Telescopes and Camera Optics

TL;DR

This paper reviews the optical design considerations for the CMB-S4 large aperture telescopes, focusing on the crossed Dragone and three-mirror anastigmat designs, including lens corrections and prototype comparisons.

Contribution

It introduces biconic lens corrections for the crossed Dragone optics and compares these with the three-mirror anastigmat designs being prototyped.

Findings

Biconic lens corrections improve diffraction-limited performance.

Comparison shows differences in optical performance between the two telescope designs.

Prototyping efforts are underway for the camera optics of both designs.

Abstract

CMB-S4, the next-generation CMB observatory, will deploy hundreds of thousands of detectors to enable mapping the millimeter-wavelength sky with unprecedented speed. The large aperture telescopes for CMB-S4 consist of six-meter diameter crossed Dragone designs and a five-meter diameter three-mirror anastigmat. The two-mirror crossed Dragone design requires astigmatism corrections in the refractive optics to achieve diffraction-limited performance. We present biconic lens corrections for the CMB-S4 crossed Dragone camera optics and compare these designs to the camera optics for the three mirror anastigmat, as the optical designs of the cameras for these telescopes are being prototyped.