About Satellites

About the Communications satellite

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An Advanced Extremely High Frequency communications satellite relays secure communications for the United States and other allied countries.

Communications Satellites act as the middleman in the realm of telecommunications. These satellites are specifically designed to relay information from a source to a receiver. Types of information that can be transferred include: television, telephone, radio, internet, and military. As of May 11, 2015, there are over 2,000 communications satellites in Earth’s orbit that are being used by private and government organizations.
In order to communicate wirelessly, signals must be sent using electromagnetic waves. However, these waves cannot bend around the curvature of the Earth. So, in order for people to communicate over long distances, a satellite (or multiple satellites) must be used to help redirect the signals.
There are two major classes of communications satellites. The first class is called the “passive satellite”. This type of satellite only redirects the signal coming from the source, and points in the direction of the receiver. With passive satellites, the transmitting signal has the tendency to be weak. This is because, as the electromagnetic wave moves through the atmosphere, particles will interrupt the wave and cause it to be muffled. Active satellites, on the other hand, allow for a signal that is much more clear. These satellites can take a signal that they receive, and amplify it to make it clearer. However, these satellites will often times amplify unwanted signals. Because of this, they also need a processor on board. A processor will filter out any of the unwanted amplified signals before sending it back down to earth.
There are three major ways in which communications satellites orbit the Earth. One of these orbits is called geosynchronous Earth orbit (GEO), which is 19,300 nautical miles from Earth’s surface. This orbit has the special characteristic in which satellites placed in this orbit can “stand still” with respect to a certain location on earth. That is, if a viewer on Earth were to look up into the sky and spot a satellite in GEO, it would seem as if it isn’t moving. Below GEO is medium Earth orbit (MEO). It ranges from 500-1200 nautical miles above Earth. Below MEO is low Earth orbit (LEO) and is about 200 nautical miles above Earth. MEO and LEO are not able to keep satellites “stationary” like GEO, so more satellites would be needed to cover a certain area. However, they transmit clearer signals because of their relatively small distance to the earth. In this case, the contractor must make a decision to use more satellites in order to have a clearer signal, or use one satellite while having a muffled signal.
The electromagnetic signals that communication satellites work with, have a large spectrum of wavelengths and frequencies. To keep these waves from interfering with one another, the United States and other international organizations have certain rules and regulations describing which wavelength a certain company or group can use. By separating out wavelengths, communication satellites will have minimal interference and be able to communicate effectively.    




^{As published on ; 11th June 2005}