Near-Earth asteroid

Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earth's orbit. A few tens of thousands have been found. Sometimes one crashes into earth. We try to find out if any are going to hit Earth using Asteroid impact prediction. Two near-Earth asteroids have been visited by spacecraft: 433 Eros, by NASA's Near Earth Asteroid Rendezvous probe and 25143 Itokawa, by the JAXA Hayabusa mission.