Intercontinental wireless data communications have been made possible and relative ease with the advent of satellite communications. Satellite communications basically employs microwave capabilities with a spacecraft placed in orbit around the earth as a repeater from one earth station to another. Basically, any object in outer space that is capable of bouncing signals from its surface back to the earth can be considered a satellite, which is why the moon was the first satellite transponder. Satellite communications is not a complex idea but its implementation is not simple. It is composed of two main components: payload and platform.

The payload of a satellite, an artificial satellite, refers to the data communications equipment installed in the craft. The platform consists all the other parts that are needed to navigate, maintain ambient conditions, energy supply and move the whole craft depending on commands given by the control center in earth. Positioning of satellites have been possible with the use of Keplerís laws.

Keplerís laws determine the way planets move around the sun. It is summarized into three. The first law states that planetary orbits are elliptical with the sun at the focus. The second law states that the radius vector from the sun to a planet sweeps equal areas in equal times. The third law states that ratio of the square of the period of revolution and the cube of the ellipse semi-major axis is the same for all planets. With this in mind, satellite orbits can be theoretically calculated. There are a total of three satellite orbits: elliptical orbits, circular orbits and circular orbits with zero inclination(equatorial orbit).

There are many ways to classify satellites. If they are categorized according to the way they handle signals, we have a passive and an active satellite. A passive satellite acts like a mirror in space that bounces off signals sent to it. An active, on the other hand, is like a repeater that can amplify the signal and transmit it back to the earth. If satellites are classified according to altitude of orbit, we have low-earth orbiting (otherwise known as nonsynchronous satellite), medium altitude satellites and geosynchronous altitude. There are other ways such as one depending on orbital pattern, territorial coverage and services.

Posted 2010-12-14 and updated on Dec 14, 2010 7:37am by crisd

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