[astro-ph.EP] 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.
Overview of the end-to-end modeling and retrieval framework used in this work. The starshade design (Section 2.1) and simulated modern Earth atmosphere (Section 2.2) are used as inputs to the simulated observations (Section 2.3), which are generated over a range of system inclinations, phase angles, and exozodiacal dust density. The resulting observations are post-processed to generate the spectral data (Section 2.4) that are used for the spectral retrievals and sensitivity analysis (Sections 3, 4). — [astro-ph.EP]
Zahra Ahmed, Stuart Shaklan, Mario Damiano, Armen Tokadjian, Edward W. Schwieterman, Simone D’Amico
Comments: 20 pages, 12 figures, Submitted to The Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2610.17377 [astro-ph.EP] (or arXiv:2610.17377v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2610.17377
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Submission history
From: Zahra Ahmed
[v1] Mon, 12 Oct 2026 20:35:37 UTC (13,112 KB)
https://arxiv.org/abs/2610.17377
Astrobiology,
