[논문 리뷰] The EXoplanet Climate Infrared TElescope (EXCITE): A balloon-borne mission to measure spectroscopic phase curves of transiting hot Jupiters

Timothy D. Rehm, Caitlyn Altermatt외 27명|arXiv (Cornell University)|2026. 02. 04.

Astro and Planetary Science인용 수 0

한 줄 요약

EXCITE is a balloon-borne 0.5 m telescope with a near-infrared spectrograph (0.8–3.5 µm, R~50) designed to measure full-orbit spectroscopic phase curves of transiting hot Jupiters from long-duration balloon flights, improving atmospheric characterization and GCM constraints.

ABSTRACT

The EXoplanet Climate Infrared TElescope (EXCITE) is a balloon-borne mission dedicated to measuring spectroscopic phase curves of hot Jupiter-type exoplanets. Phase curve measurements can be used to characterize an exoplanet's longitude-dependent atmospheric composition and energy circulation patterns. EXCITE carries a 0.5 m primary mirror and moderate resolution diffraction-limited spectrograph with spectral coverage from 0.8--3.5 um. EXCITE is designed to fly from a long-duration balloon (LDB). EXCITE will observe through the peak of a target's spectral energy distribution (SED) and through spectral signatures of hydrogen and carbon-containing molecules. In this paper, we present the science goals of EXCITE, detail the as-built instrument, and discuss its performance during a 2024 engineering flight from Fort Sumner, New Mexico.

연구 동기 및 목표

• Characterize longitude-dependent atmospheric composition and energy transport in hot Jupiters.
• Demonstrate phase-resolved spectroscopy from a stratospheric balloon platform.
• Provide continuous, high-st stability observations across the SED peak to reduce systematics.
• Bridge spectral gaps between HST/WFC3 and JWST/Spitzer phase-curve data with broad NIR coverage.

제안 방법

• A 0.5 m primary mirror with a moderate-resolution NIR spectrograph (0.8–3.5 µm) achieving R ~ 50.
• Balloon platform from long-duration balloon (LDB) near-polar flights to enable continuous stare observations.
• Phase-resolved spectroscopy to obtain full-orbit exoplanet spectra, including transit and secondary eclipse, for multiple targets.
• Cryogenic receiver and HgCdTe detectors within a 120/130 K temperature regime to minimize instrumental background.
• Instrumentation stability and pointing achieved via a gondola/ACS with a fine guidance system (FGS) and star cameras, enabling ~50 mas sensitivity at the focal plane.
• Noise simulations and data-reduction pipelines to assess instrumental effects and systematic errors.

실험 결과

연구 질문

• RQ1 How can spectroscopic phase curves in the 0.8–3.5 µm range constrain longitudinal temperature and chemical gradients in hot Jupiters?
• RQ2 What atmospheric properties (e.g., heat recirculation, albedo, cloud coverage) can be inferred from phase curve amplitudes and phase offsets across the EXCITE band?
• RQ3 To what extent does continuous LDB-based observation improve phase-curve completeness and mitigate observation gaps relative to space-based facilities?
• RQ4 How do EXCITE observations inform and improve General Circulation Models (GCMs) for hot Jupiter atmospheres?

주요 결과

• EXCITE provides broad 0.8–3.5 µm coverage with spectral resolution sufficient for phase-resolved spectroscopy of hot Jupiters.
• A long-duration balloon flight enables continuous point-and-stare observations, reducing gaps and thermal settling times common in LEO platforms.
• The instrument targets transit and secondary eclipse phases to derive day/night brightness maps and phase offsets across wavelengths.
• Phase curves across the EXCITE band probe multiple molecular and continuum opacity sources, aiding molecular abundance and temperature-pressure profiling.
• The mission aims to significantly increase the number of full-orbit spectroscopic phase curves, informing atmospheric dynamics and energy budgets via GCM comparisons.