Jyrki T. J. Penttinen
Satellite can refer to the manmade equipment placed at some of the useful orbits of the object like Earth or Mars. Satellite can also be any other special piece that is located at the orbit. As an example, Mars is orbited by two very small satellites, Phobos and Deimos. It is assumed that these satellites are based on captured asteroids with dark, carbon-rich rock .
In the case of terminology of, for example, spaceflights, a satellite is an object which has been placed into orbit by human endeavor. These satellites are also called artificial satellites. The other variant, natural satellite may refer to, for example, Moon.
The first artificial satellite made by human beings was the Sputnik 1, launched by the Soviet Union in 1957. After that, the number of satellites orbiting the Earth has risen to several thousands. These artificial satellites represent the international cooperation of over 50 countries. Despite the high number of artificial satellites, only a few hundred of them are actually functional and operational. The rest are unused, either complete or fragmented satellites that are considered merely space debris.
Along with the development of satellite techniques, the importance of location based services has increased rapidly since the initial deployment of GPS back in 1990s. Along with the development of mobile communications networks, an increasing set of applications utilizes ...