If you keep seeing new ones every single year, that can give you an idea of how much there are left to find. As you get smaller and smaller in size, there's more andmore of them. So at first they were just asked to look for all the asteroids that were a kilometer or larger. And then in two thousand five a congress asked nassau to look for anything a hundred forty meters en larger. An hundred forty meters, i s like the size of a skyscraper. I guess you can call them medium sized asteroids, but i would not want to be up close near one,. What would that do if it hit earth? That be an extinction event.