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Henrietta: A novel ground-based spectrograph to routinely characterize exoplanet atmospheres

Presentation #102.383 in the session Poster Session.

Published onJun 20, 2022
Henrietta: A novel ground-based spectrograph to routinely characterize exoplanet atmospheres

To date, we have confirmed ~5000 exoplanets yet have only studied ~100 of their atmospheres spectroscopically. The near-infrared (NIR) is one of the most important wavelength ranges to characterize atmospheric composition, yet we do not have a way to routinely obtain precise broadband spectra beyond building space-based telescopes. Ground-based telescopes offer a unique pathway out of this predicament, yet remain untapped as a combination of unmitigated noise and systematics prevent precise constraints on atmospheric properties from being obtained. In this talk I’ll present the design of Henrietta, a high-precision spectrograph that will perform transit spectroscopy of exoplanets on the undersubscribed 1-m Swope Telescope at Las Campanas Observatory in Chile. Henrietta can observe a wavelength range of 0.6–2.4um, with spectral resolutions ranging from 200–500, and is designed to limit all sources of noise and systematics to 1.5x the photon limit when performing differential spectrophotometry. This is primarily accomplished through use of a diffuser, which averages over the intra-pixel sensitivities in H2RG detectors, a 25’ x 3’ field of view for access to bright comparison stars, and a novel method to correct for atmospheric scintillation. Henrietta’s design is fundamentally driven by a noise budget, which I will describe along with the optical design. I will discuss Henrietta’ simulated performance, which amounts to a precision of 100 ppm in 1 hour for a J = 8.5 magnitude star at R = λ/Δλ = 100. This level of precision combined with the ample telescope time will make Henrietta a powerful means to routinely observe exoplanet atmospheres, prioritize targets for JWST, and inform the next generation of transit and eclipse spectroscopy instruments. Henrietta is currently in its integration and testing phase and will begin commissioning in Fall 2022


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