Large Resolution-Weighted Etendue Space Telescope Designs Categorized by Tertiary Mirror Location Diversity

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 ´etendue alone does not fully capture the efficiency with which resolved and deblended information can be acquired. We introduce a resolution-weighted etendue 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 etendue and imaging throughput, making them well-suited for precision cosmological and astrophysical measurements.