Why don’t satellites clash into each other?

More than several thousands of satellites are orbiting around the Earth. There are various types of satellites, so the orbit and the altitude are different depending on each satellite’s role.

For example, weather satellites etc. are spinning in “geostationary orbit” at an altitude of about 36,000 km above the equator at a speed of 3 kilometers per second. Since the cycle of geostationary orbit satellites is 24 hours, same as the Earth’s rotation, the satellite always looks like staying the same spot from the ground. Earth observation satellites are flying at an altitude of about 500 – 1,000 km and observe the whole earth within several days. Pictures taken from space and various information are delivered to the ground as satellite data and utilized for our daily life.

In this way, the orbit of the satellites varies depending on the role and when and where they pass through are well-determined. The satellites do not clash into each other because they are constantly monitored from the ground not to deviate from the orbit.