Most satellites and other artificial objects we have put in space are in Low Earth Orbit, with an altitude never more than about one-third of the radius of Earth.
What is an orbit?
If you throw a stone horizontally, it will land some distance away from you. If you throw it at higher speed, it will land further away from you.
What if you throw the stone so fast that it goes all the way around the Earth? That’s what happens with satellites: they are going fast enough, that they don’t fall to the Earth and keep going around it.
The time it takes to go around the Earth (the orbital period) increases with the orbit altitude.
What is Low Earth Orbit (LEO)?
Low Earth orbits have specific altitudes.
- Objects in LEO have altitudes between 200 km and 2000 km above the Earth’s surface.
- Objects in LEO complete a full orbit of the Earth in 90 to 120 minutes.
For comparison, the Moon has an altitude (distance to Earth) of about 380000 km and takes over 27 days (656 hours) to complete an orbit.