telescopes on the earth can only see part of the sky. they won't be able to see any asteroids coming from near the direction of the sun because of the blue sky during the day. a telescope in space doesn't have that problem. it can see much more of the sky around earth. it can keep looking all through the day and night and there are no clouds or rain in space. telescopes in space can also use infrared heat radiation to find asteroids. looking for that kind of light is an especially good way of finding asteroids. this method doesn't work on earth because the air is too warm. heat radiation from warm air hides the heat radiation that comes from the asteroids. space telescopes are better in a lot of ways, but they cost more money. also, they don't last as long as telescopes on the ground.