More than 50% of the known asteroids in our solar system have been discovered through this program.
No known asteroid is expected to hit the Earth in that time.
To date, the Themis family comprises approximately 535 known asteroids.
The first known asteroids are discovered in this decade:
The method relies on the fact that the large number of known asteroids means they will occasionally move past one another at very close distances.
By 1851 there were 15 known asteroids, all but one with their own symbol.
(That potential is almost always dismissed; only one known asteroid has even a slight chance of hitting the planet, on March 16, 2880).
Toutatis is the largest known asteroid to pass this close to Earth.
During this time the four known asteroids were counted among the planets, and each had its own planetary symbol.
The diameter of Ceres, the largest known asteroid, is 590 miles.