ELT instrumentation for seeing-limited and AO-corrected observations: A comparison

TL;DR

This paper discusses the design challenges of instrumentation for extremely large telescopes (ELTs) that operate across various resolutions and wavelengths, highlighting differences between seeing-limited and diffraction-limited systems.

Contribution

It provides a comparative analysis of ELT instrumentation challenges for seeing-limited, AO-corrected, and diffraction-limited observations across different wavelengths.

Findings

Seeing-limited instruments tend to be large and heavy.

Diffraction-limited instruments have unique design challenges.

AO performance is limited at visible wavelengths.

Abstract

The next generation of large ground-based optical and infrared telescopes will provide new challenges for designers of astronomical instrumentation. The varied science cases for these extremely large telescopes (ELTs) require a large range of angular resolutions, from near diffraction-limited performance via correction of atmospheric turbulence using adaptive optics (AO), to seeing-limited observations. Moreover, the scientific output of the telescopes must also be optimized with the consideration that, with current technology, AO is relatively ineffective at visible wavelengths, and that atmospheric conditions will often preclude high-performance AO. This paper explores some of the issues that arise when designing ELT instrumentation that operates across a range of angular resolutions and wavelengths. We show that instruments designed for seeing-limited or seeing-enhanced observations have particular challenges in terms of size and mass, while diffraction-limited instruments are not as straightforward as might be imagined.