Image: Center for Satellite Engineering Research
Other satellites relay millions of telephone conversations, keep a watch on the weather, monitor crops and the environment, and tell pilots and ship captains their precise positions. And, of course, there are a fair number of others owned by various governments, which decline to discuss their purposes.
But satellites are only part of the picture--there is also a lot of junk up there. The flotsam and jetsam of the space age include the bodies of spent rockets that carried satellites to orbit, satellite fragments, as well as discarded nose cone shrouds, lenses or hatch covers. These account for an additional 6,000 or so man-made objects soaring around the planet.
To avoid collisions with the space shuttles or expensive new satellites, all this space clutter is closely watched by the U.S. Air Force Space Command. It collects more than 70,000 observations each day on anything orbiting Earth, from the size of a baseball to the Mir space station. These data are compiled by the National Aeronautics and Space Administration into a document called the Satellite Situation Report, which lists both objects in orbit and objects recently departed.