We talked about different orbits in space last time. Let's talk about their features and where are the artificial satellites!

International Space Station (ISS) orbits around the Earth, and its home in space is the Low Earth orbit (LEO) which is quite close to the Earth. Near-Earth satellites orbit faster, for instance ISS orbits the Earth once about every 90 minutes so a "day" there only has 90 minutes! Taking advantage of their closeness to Earth, satellites in LEO can take high-resolution photos of our home planet.

The GPS satellites that we use a lot operate in the Medium Earth orbit (MEO). MEO lies between LEO and geostationary orbit (GEO). Satellites in MEO semi-synchronise with the Earth's movement. They complete an orbit around the Earth once every 12 hours. On the other hand, satellites in GEO move at the same speed as the Earth's rotation thus their positions are fixed relative to the ground. Hence, the antennas that receive and transmit signals from the satellites can be fixed. Some communication satellites and weather satellites are in GEO.

Lagrange points are much farther away from the Earth than the other orbits. Satellites at the Lagrange points are balanced by the gravitational forces of the nearby celestial bodies so they can stay in the corresponding orbit with the least amount of energy. Some space telescopes, such as solar telescopes and the upcoming James Webb Space Telescope are at Lagrange points.

There are many man-made objects in space and many different orbits. Sometimes collisions do happen! What are the fates of those satellites? If you want to know more, pay attention to our posts!