DUET: Design of a simultaneous InGaAs--CCD split-beam imager for ultra-cool dwarf exoplanet transit survey
arXiv:2607.14772
The paper presents the design of DUET, a dual-channel imager that simultaneously records visible light with a CCD and near‑infrared light with an InGaAs detector to observe transiting exoplanets around ultra‑cool dwarf stars.
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\,\textmu 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.
12 pages, 8 figures, 2 Tables, proceedings of SPIE Astronomical Telescopes + Instrumentation 2026, 14149-438