The Satellites that Surround Earth.

Thousands of satellites orbit the Earth. Costing billions of dollars, this swarm of high altitude robots is now vital to communication , orientation , and imaging both Earth and space . One common type of orbit is geostationary where a satellite will appear to hover above one point on Earth's equator. Geostationary orbits are very high up -- over five times the radius of the Earth -- and possible only because the satellite orbital period is exactly one day. It is usually cheaper to place a satellite in low Earth orbit, around 500 kilometers, just high enough to avoid the effect of Earth's atmosphere . The above animated sequence starts by showing the halo of Earth's satellites , including the ring at geostationary, and finishes by zooming in on the only one currently hosting humans: the International Space Station .