Man-made earth satellite refers to an unmanned spacecraft that orbits the earth more than once, referred to as artificial satellite for short. Man-made satellite is the spacecraft with the largest number of launches, the widest use and the fastest development. As the saying goes, "stand high and see far" can very briefly summarize the advantages of artificial satellites.

First, the satellite flies in orbit. For the earth, stand high and have a big view. It is a veritable "clairvoyance" and "windward ear". It is very useful to observe with it. According to different observation objects and uses, artificial satellites can be divided into several categories: meteorological satellites, resource satellites, ocean satellites and reconnaissance satellites belong to remote sensing satellites, space exploration satellites and astronomical satellites belong to scientific experimental satellites, as well as communication satellites and technical experimental satellites.

Secondly, satellites can also be used for communication. Compared with ordinary terrestrial communication, satellite communication has the advantages of large communication capacity, wide coverage, long communication distance, high reliability, good flexibility and low cost. Satellite communication technology has a strong military color and has an absolute advantage in strategic communication and tactical communication.

In addition, the space environment in which the satellite is located is a special environment of microgravity and high radiation, which is very different from the environment on earth. Therefore, we can use this difference to carry out scientific experiments such as biological breeding and material processing, and often get miraculous results.

Satellites can also be used for battlefield surveillance, missile early warning, national security and other tasks.