The 35th annual conference on Astronomical Data Analysis Software & Systems 2025 in Görlitz, Germany

Stellar occultations are a powerful method for determining the physical properties of small Solar System bodies such as asteroids, Centaurs, and trans-Neptunian objects (TNOs). By recording the precise moments a body passes in front of a background star, occultations provide accurate measurements of its projected profile, enabling size and shape reconstruction, especially when combined with rotational lightcurve data. In addition, they can probe the surrounding environment and reveal features such as satellites, rings, or atmospheres. They also deliver astrometric positions at the sub-milliarcsecond level, highly valuable for orbit determination. Stellar occultations can be used to study the occulted stars themselves - for example, by measuring stellar angular diameters, resolving close binaries, determining the position, brightness, and separation of components, or even revealing unexpected multiplicity.

Asteroid occultations have been observed for decades, often through amateur and pro–am collaborations. Advances in orbital computations and modern stellar catalogs like Gaia have extended this technique over the past 15+ years to more challenging targets, including TNOs, near-Earth objects (NEOs), and comets. Accurate predictions, effective dissemination of events, systematic observation collection, and long-term archiving are essential to maximize the scientific return.

To address these needs, we developed CORA (Collaborative Occultation Resources and Archive), a modern web-based platform supporting the full occultation workflow. CORA provides event predictions using ephemerides and orbits from both JPL Horizons and independent orbital computations performed within the system. It archives and presents observations in user-friendly and machine-readable formats, ensures interoperability with other tools, and delivers rapid feedback to observers to improve data quality. For special campaigns, customized prediction sets can also be distributed to the community.