Low-Earth Orbit

The first type of orbit typically used by communications satellites is low-Earth orbit, or "LEO." A satellite in LEO travels at altitudes about three hundred to one thousand two-hundred and fifty miles above the Earth's surface. At these low altitudes, the satellite must travel very fast to counteract the Earth's gravity and avoid being pulled into the Earth's atmosphere.

Objects in low-Earth orbit move very fast. For example, a satellite in LEO travels at a speed of over 15,000 miles per hour. As a result, satellites in LEO can go around the Earth in about two hours.

Satellites in LEO do not appear fixed at a certain point in the sky. Instead, antennas must be able to track the satellite in the sky, or the antenna must be able to see a very large portion of the sky. Frequently, LEO satellites are deployed in large numbers, so that satellites can hand off customer's traffic to one another as one satellite disappears over the horizon and a new satellite appears.