The Catalina Sky Survey (CSS) is a survey to discover near-Earth objects (NEOs), in particular potentially hazardous asteroids (PHAs) that may pose a threat of impact. The survey is conducted at the Steward Observatory's Catalina Station, which is located near Tucson, AZ. It is a NASA funded project.


CSS has discovered more than 45% of the more than 18,000 known NEOs. Additionally, the Catalina Real-Time Transient Survey (CRTS) imagery from CSS’s extensive sky coverage is being used to search for optical transient celestial phenomena including supernovae, variable stars, active galactic nuclei, blazars, and the like. For that reason, CSS is very popular also amongst professional and amateur variable star researchers.