Geostationary satellites revolve around the planet at the same speed as the Earth. Therefore, from the outside they look "hanging" in the sky at one point. In order for satellites to correct their orbit, they are equipped with rocket engines.
Artificial satellites of the Earth, revolving around it in a geostationary orbit, for terrestrial inhabitants look like a point hanging motionless in the sky. This is due to the fact that they rotate with the same angular velocity with which the Earth rotates.
Since in the system of coordinates we are accustomed to during rotation, the satellite does not change either the azimuth or the height above the horizon line, it seems to "hang" motionless.
Geostationary orbit
Geostationary satellites are located at an altitude of about 36 thousand kilometers above sea level - it is this orbital diameter that allows the satellite to complete a full revolution in a time approaching the Earth's day (about 23 hours 56 minutes).
A satellite rotating in a geostationary orbit is affected by many factors (gravitational disturbances, the elliptical nature of the equator, the inhomogeneous structure of earth's gravity, etc.). Because of this, the satellite's orbit changes and needs to be constantly corrected. To keep the satellite in the right place in orbit, it is equipped with a low-thrust chemical or electric rocket engine. Such an engine is turned on several times a week and corrects the position of the satellite. Considering that the average service life of a satellite is about 10-15 years, it can be calculated that the rocket fuel required for its engines should be several hundred kilograms.
Science fiction writer Arthur Clarke was one of the first to popularize the idea of using the geostationary orbit for communication. In 1945, his article on this topic was published in the Wireless World magazine. Because of this, the geostationary orbit in the Western world is still called the "Clarke Orbit".
Although geostationary satellites appear to be stationary, they actually rotate in sync with the planet at more than three kilometers per second. They cover a distance of 265,000 kilometers per day.
LEO satellites
If the satellite's orbit is reduced, the power of the signal transmitted by it will increase, but it will inevitably begin to rotate faster than the earth and will cease to be geostationary. Simply put, you will have to "catch" it, constantly reorienting the receiving antenna. To avoid this, it is enough to launch several satellites in one orbit - then they will replace each other and the antenna will not have to be reoriented. This principle was applied to the organization of the Iridium satellite system. It includes 66 low-orbit satellites rotating in six orbits.
