Ultraviolet Reflected-Light Spectroscopy of Modern Earth Analogs with Starshade Observations
Abstract
Characterizing rocky, habitable zone planets in reflected light is a key science objective for future direct imaging missions, and the ultraviolet (UV) is uniquely suited for supporting the characterization of Earth-like atmospheres. The Hartley-Huggins ozone band at 0.25 μm remains detectable at low spectral resolution down to 0.1% PAL O2, providing a sensitive proxy for oxygen-bearing chemistry even for Proterozoic-like atmospheres where the visible and near-infrared O2 features become inaccessible. This work uses an end-to-end framework for UV starshade spectroscopy of modern Earth analogs that integrates high-fidelity observation simulation, conservative post-processing, and Bayesian spectral retrieval to quantify ozone detection significance. The framework is applied across 108 simulated scenes spanning a range of planet phase angles, system inclinations, and exozodiacal dust densities. The results establish that robust ozone detection with UV-only, R=7 reflected light spectroscopy requires a photometric SNR ∼ 30. UV starshade observations with the Habitable Worlds Observatory achieve this threshold within 3-day integrations for solar-type systems at 10 parsecs with inclinations up to 60∘ at favorable phases (≤ 90∘). Above this SNR threshold, ozone detections are robust to systematic bias from imperfect exozodi calibration within ∼30%, and the median retrieved ozone abundance remains accurate to within one order of magnitude of the true value.
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BibTeX
@misc{ahmed2026ultraviolet,
title = {{Ultraviolet Reflected-Light Spectroscopy of Modern Earth Analogs with Starshade Observations}},
author = {Zahra Ahmed and Stuart Shaklan and Mario Damiano and Armen Tokadjian and Edward W. Schwieterman and Simone D'Amico},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.17377},
eprint = {2610.17377},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.17377},
}
RIS
TY - UNPB
TI - Ultraviolet Reflected-Light Spectroscopy of Modern Earth Analogs with Starshade Observations
AU - Zahra Ahmed
AU - Stuart Shaklan
AU - Mario Damiano
AU - Armen Tokadjian
AU - Edward W. Schwieterman
AU - Simone D'Amico
PY - 2026
DA - 2026/10/12
PB - arXiv
DO - 10.48550/arxiv.2610.17377
UR - https://arxiv.org/abs/2610.17377
AB - Characterizing rocky, habitable zone planets in reflected light is a key science objective for future direct imaging missions, and the ultraviolet (UV) is uniquely suited for supporting the characterization of Earth-like atmospheres. The Hartley-Huggins ozone band at 0.25 μm remains detectable at low spectral resolution down to 0.1% PAL O_2, providing a sensitive proxy for oxygen-bearing chemistry even for Proterozoic-like atmospheres where the visible and near-infrared O_2 features become inaccessible. This work uses an end-to-end framework for UV starshade spectroscopy of modern Earth analogs that integrates high-fidelity observation simulation, conservative post-processing, and Bayesian spectral retrieval to quantify ozone detection significance. The framework is applied across 108 simulated scenes spanning a range of planet phase angles, system inclinations, and exozodiacal dust densities. The results establish that robust ozone detection with UV-only, R=7 reflected light spectroscopy requires a photometric SNR ∼ 30. UV starshade observations with the Habitable Worlds Observatory achieve this threshold within 3-day integrations for solar-type systems at 10 parsecs with inclinations up to 60^∘ at favorable phases (≤ 90^∘). Above this SNR threshold, ozone detections are robust to systematic bias from imperfect exozodi calibration within ∼30%, and the median retrieved ozone abundance remains accurate to within one order of magnitude of the true value.
ER -