Exep: Ultraviolet Starshade Capabilities for ExoEarth Imaging

The next generation of exoplanet direct imaging missions will focus on detecting and characterizing Earth-like planets across the ultraviolet (UV), optical, and near-infrared (NIR) spectrum. Starshades operating in the UV offer high throughput, high contrast, and broad spectral bandwidth, making them a valuable complement to coronagraphs as a characterization instrument. This work introduces high-fidelity simulations of UV starshade observations of an Earth-twin orbiting a Sun-like star at 10 parsecs. The simulations incorporate conservative estimates of starshade-specific systematics such as petal shape and position errors, solar and surface glint, micrometeoroid holes, formation flying errors, and contaminated edges, alongside local zodiacal dust and resonant exozodiacal debris disks. To estimate the planetary signal from the simulated observation, this work implements a post-processing pipeline consisting of imperfect starshade calibration, parametric exozodi estimation and a matched filter. Finally, this work presents a sensitivity analysis of a starshade’s ability to recover high signal-to-noise measurements of an Earth-like planet as a function of system inclination, planet phase angle, and exozodiacal dust density. This approach is applied to a 35-meter UV starshade optimized for the future Habitable Worlds Observatory (HWO). The results for the HWO starshade indicate that is possible to achieve an SNR ≥ 10 in under three days of observation across a wide range of cases. For inclinations ≤ 30◦, an SNR ≥ 10 is possible for systems with up to 50 times the Solar System’s dust density, or 50 zodis. This performance extends to 20 zodis for 60◦ inclined system, even at unfavorable crescent planet phases. Evaluating the impact of residual noise on the extracted spectra with resolution R = 10 at 250 nm reveals that it is possible to obtain measurements of the 0.25μm ozone feature with between 1%−5% error for inclinations ≤ 60◦ and ≤ 20 zodis.