Work

Ultraviolet Reflected-Light Spectroscopy of Modern Earth Analogs with Starshade Observations

Year: 2026

Type: preprint

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 $0.25 ~μ\mathrm{m}$ remains detectable at low spectral resolution down to $0.1\%$ PAL $\mathrm{O}_2$, providing a sensitive proxy for oxygen-bearing chemistry even for Proterozoic-like atmospheres where the visible and near-infrared $\mathrm{O}_2$ 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 $\mathrm{SNR} \sim 30$. 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 $60^\circ$ at favorable phases ($\leq 90^\circ$). Above this SNR threshold, ozone detections are robust to systematic bias from imperfect exozodi calibration within $\sim30\%$, and the median retrieved ozone abundance remains accurate to within one order of magnitude of the true value.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2610.17377

Authors: Ahmed, Zahra, Shaklan, Stuart, Damiano, Mario, Tokadjian, Armen, Schwieterman, Edward W., D'Amico, Simone

Institutions: Stanford University, California Institute of Technology, Jet Propulsion Laboratory, University of California, Riverside

Language: English

Topic: Stellar, planetary, and galactic studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Indian Council of Agricultural Research, National Institutes of Health, Jet Propulsion Laboratory, Stanford Research Computing Center, Stanford University

Awards: Acquisition of a Scalable Storage Cluster for Data Intensive NIH Research, G23037955, G2676722403, Research Infrastructure: MRI: Acquisition of a Big Data HPC Cluster for Interdisciplinary Research and Training, MRI: Acquisition of a Big Data Compute Cluster for Interdisciplinary Research, Graduate Research Fellowship Program (GRFP), G6605062335, G6661425536, G830101876, G8438684293

OpenAlex ID: W7221770233

Cites: 23

Cited by:

Related to: 10