DUET: Design of a simultaneous InGaAs--CCD split-beam imager for ultra-cool dwarf exoplanet transit survey

arXiv:2607.14772 · astro-ph.IM, astro-ph.EP, astro-ph.SR · Submitted 2026-07-16 · Read on arXiv

Peter P. Pedersen, Clark Baker, Karolina Dziewiecka, Mathias Beck, Michaël Gillon, Amaury H. M. J. Triaud, Didier Queloz

astro-ph.IM, astro-ph.EP, astro-ph.SR

Submitted: 2026-07-16

Comments: 12 pages, 8 figures, 2 Tables, proceedings of SPIE Astronomical Telescopes + Instrumentation 2026, 14149-438

Code: https://github.com/ppp-one/mphot

License: http://creativecommons.org/licenses/by/4.0/

The gist: We present the design of DUET, a dual-channel imager being built for the SPECULOOS-Southern Observatory (SSO) to detect and characterise transiting terrestrial exoplanets orbiting ultra-cool dwarfs.

Terminology

Abstract

We present the design of DUET, a dual-channel imager being built for the SPECULOOS-Southern Observatory (SSO) to detect and characterise transiting terrestrial exoplanets orbiting ultra-cool dwarfs. A dichroic beamsplitter at 955,nm directs visible light to a deeply-depleted silicon CCD and near-infrared light to a CMOS-based InGaAs detector, enabling fully simultaneous photometry with bandpasses from 0.4 to 1.7, m. The near-infrared filters have been chosen to suppress sensitivity to atmospheric precipitable water vapour (PWV) variability, a dominant source of correlated noise in ground-based infrared photometry of cool stars. We describe the optical and mechanical architecture, the dichroic and filter selection, the choice of detectors, and the control system.

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