MIRECLE: Science Yield for a Mid-infrared Explorer-class Mission to Study Nontransiting Rocky Planets Orbiting the Nearest M Stars Using Planetary Infrared Excess

Abstract

Abstract Recent investigations have demonstrated the potential for utilizing a new observational and data-analysis technique for studying the atmospheres of nontransiting exoplanets with combined light that relies on acquiring simultaneous, broad-wavelength spectra and resolving planetary infrared emission from the stellar spectrum through simultaneous fitting of the stellar and planetary spectral signatures. This new data-analysis technique, called planetary infrared excess (PIE), holds the potential to open up the opportunity for measuring mid-infrared (MIR) phase curves of nontransiting rocky planets around the nearest stars with a relatively modest telescope aperture. We present simulations of the performance and science yield for a mission and instrument concept that we call the MIR Exoplanet CLimate Explorer, a concept for a moderately sized cryogenic telescope with broad wavelength coverage (1–18 μm) and a low-resolution (R ∼ 50) spectrograph designed for the simultaneous wavelength coverage and extreme flux measurement precision necessary to detect the emission from cool rocky planets with PIE. We present exploratory simulations of the potential science yield for PIE measurements of the nearby planet Proxima Centauri b, showing the potential to measure the composition and structure of an Earth-like atmosphere with a relatively modest observing time. We also present overall science yields for several mission architecture and performance metrics, and discuss the technical performance requirements and potential telescope and instrument technologies that could meet these requirements.