A communication satellite is the repeater placed above the atmospheric surface of the earth. It is used for long distance communication. It is expensive, slow and has chance of error during transmission. In this media, a ground station sends data in the form of radio signal toward the satellite, which is called as uplink. Satellite receive signal, amplifies it and forward towards receiving ground station, which is called as downlink.
HISTORY ABOUT SATELLITES
The first satellite in space that was launched by Soviet Union in 1957 was Sputnik 1. NASA has launched lots of satellites since its inception. It started with Explorer 1 satellite in 1958 (USA’s first artificial satellite). It had a sensor that could measure high-energy particles in space called cosmic rays. NASA then continues in its series of expeditions and launched Explorer 6 in 1959. Explorer 6 gave the first picture of Earth. It was followed by TIROS-1 in 1960 which gave first TV picture of Earth from space.
There are two types of satellites
Natural satellites are the one which preexist in universe. For instance, moon is a natural satellite that surrounds Earth.
These are man-made satellites that have been projected into the solar system to surround some planet for some particular purpose. These are the reasons behind that we are able to view live cricket matches, existence of dish televisions. These satellites communicate with Earth by using radio waves to send signals to antenna attached to Earth. The antennas catch hold of these signals, interpret them, get the information and process it in the form that can be understood by the human mind. One example of artificial satellite being, satellite sent to Mars from Earth to study about the existence of life on Mars.