Research Article

Large resolution-weighted étendue space telescope designs categorized by tertiary mirror location diversity

¹ Department of Astronomy, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
² Center for Galaxy Evolution Research, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
³ Department of Physics and Astronomy, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
⁴ Wyant College of Optical Sciences, University of Arizona, 1630 E. University Blvd., Tucson, AZ 85721, USA
⁵ Department of Astronomy, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
⁶ Large Binocular Telescope Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 21 January 2026
Accepted: 31 March 2026

Abstract

Modern observational astronomy makes extensive use of deep, wide-field imaging and large spectroscopic surveys, defining telescope design spaces in which angular resolution, achievable depth, and survey efficiency are considered jointly rather than independently. Conventional étendue alone does not fully capture the efficiency with which resolved and deblended information can be acquired. We introduce a resolution-weighted étendue metric that provides a quantitative basis for comparing information throughput across different facilities. Applying this metric, we illustrate how accounting for angular resolution reshapes the relative placement of existing telescopes in design parameter space, with a representative space telescope design serving as an example of this shift. We consider two distinct reflective space telescope designs utilizing a variation of the three-mirror anastigmat configuration. The strategic placement of the tertiary mirror significantly influences the telescope’s form factor, enabling compact architectures for very large aperture systems. These designs achieve large resolution-weighted étendue and imaging throughput, making them well-suited for precision cosmological and astrophysical measurements.