Asteroids and comets whose orbits bring them within 120 million miles of the Sun are classified as near-Earth objects (NEOs), due to their potential to intersect with Earth’s own path through space. At NASA’s Jet Propulsion Laboratory in Southern California, the Center for Near-Earth Object Studies (CNEOS) analyzes the orbits of these objects and calculates their odds of approaching or hitting Earth. 

To compute NEO orbits, CNEOS combines telescopic observations with data weighting and modeling techniques, ensuring the highest accuracy possible with the available data. The results are archived in JPL’s Small Body DataBase (SBDB) for anyone to access. 

CNEOS hosts the Sentry system, which automatically scans asteroid catalogs and estimates which asteroids may have a chance of hitting Earth in the next 100 years. It is also home to the Scout system, which pulls potential asteroid discoveries from the NASA-funded Minor Planet Center and models the possible range of movements for these asteroid candidates before their discoveries are even confirmed. 

In addition to orbital data, CNEOS provides tools to help study NEOs, including some that are managed by JPL’s broader Solar System Dynamics group. This includes tools to help users retrieve data from the CNEOS catalog, tools to help astronomers locate asteroids and comets in the night sky, and an asteroid size estimator tool. 

Most NEOs have no chance of impacting Earth. However, if an asteroid's estimated future trajectory may take it concerningly close to Earth, CNEOS alerts NASA’s Planetary Defense Coordination Office. The planetary defense community then gets to work assessing the extent of the possible asteroid threat. 

To learn more about the role of CNEOS in detecting potentially hazardous asteroids, including in the case of the asteroid 2024 YR4, read the recent feature about how NASA science data defends Earth from asteroids.