NASA's Near-Earth Object (NEO) Surveyor mission is designed to help advance planetary defense efforts to discover and characterize most of the potentially hazardous asteroids and comets that come within 30 million miles of Earth’s orbit. These are collectively known as near-earth objects, or NEOs. NEO Surveyor consists of a single scientific instrument: a 50 centimeter (nearly 20 inch) diameter telescope that operates in two heat-sensing infrared wavelengths. It will be capable of detecting both bright and dark asteroids, which are the most difficult type to find.