What are Communications satellites?

Communication satellites receive signals from antennae on the Earth's surface, or from other satellites, amplify the signals, and beam them back to Earth. Because they are hundreds or thousands of miles up, their signals can cover a larger area than most radio or television signals broadcast on the surface, because of the Earth's curvature. (Radio waves don't go around corners well.)

Some communications satellites are in quite low orbits, around 150 miles high. Others are in "geostationary" orbits at about 22,500 miles, where their rotation around the Earth is the same speed as the Earth's rotation, so that they stay above a particular spot all the time. Most broadcast satellites for TV, phone service and satellite radio are geostationary.