Satellites - Receiving and Collecting Information

Louisa D. / Physics 337/ May 18, 1997
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[ Transmitting and Receiving Information ] [ Communication ] [ Ground Station ]
[ Commercial Uses ] [ Types of Satellites and Their Missions ]
Satellites have many important functions. One of the most basic functions is collecting and receiving information. Satellites give use much useful knowledge which can be used to help us learn about things we wouldn't normally be able to study.

Transmitting and Receiving Information:

One of the main uses of a satellite is to view things around the world that we wouldn't be able to see from our normal vantage point. The satellite would therefore be useless if we were unable to get the information from it. For this reason satellites must transmit all their information to the earth down below. "Well, how do they do that?", one might ask. The answer goes as follows. Satellites transmit information gathered by their sensors during each contact with the ground station. They contact the station using a large dish antennae which is situated on earth, at the site of the ground station. During the contacts between the satellite and ground station the satellites usually transmit information about the state of its various subsystems and its position/orientation in space.


The control center communicates constantly with the satellite by radio. The ground stations transmit and receive all radio messages. "A satellite doesn't usually receive constant direction from its control center" (World Book Multimedia Encyclopedia). Although the communication is not constant it is two way. The satellite has ability to reach the control center at all times. Often times the ground control stations send commands for the satellite to adjust its' position or change its' orbit.

Ground Station:

As you can tell ground stations are a very important part of keeping a satellite safe and on course. The two are always in touch in case of emergency. the stations are located beneath the satellites' orbit or elsewhere within the satellites' range.

Commercial Uses:

Although satellites are very important to help us learn about our world, they are also very useful for other reasons. Television broadcasters and telephone companies use satellites continuously.

Types of Satellites and Their Missions:

Artificial satellites are classified according to their mission. There are six main types of artificial satellites. They are scientific research, weather, communications, navigation, earth observation, and military. All these types are used for different reasons, they all have different functions. Scientific research satellites gather data for scientific analysis. Often they record changes in the earth and its atmosphere. Weather satellites are very helpful because they help scientists study weather patterns and forecast the weather. These satellites photograph changing cloud formations. They produce infrared images which show the amount of heat coming from the earth and clouds. This information is sent back to earth and used by scientists. Communication satellites are usually put in a high altitude orbit over a ground station. The ground station is, as mentioned earlier, equipped with a large dish antennae for transmitting and receiving signals. Navigation satellites operate in networks. Signals from a network can reach vehicles anywhere on the earth's surface. Earth observation satellites use polar orbits to map and monitor our planet's resources. Under constant illumination from the sun, they take pictures in different colors of visible light and in infrared radiation. Computers on earth combine and analyze the pictures. Scientists can then locate mineral deposits, determine the location of freshwater supplies and identify sources of pollution. Some military satellites called "spy satellites" can detect the launch of missiles, the course of ships at sea, and the movement of military equipment on the ground.


As you can tell, satellites have become one of our most important sources of information. They give us an endless amount of information that helps us understand our world. They are obviously very useful in the military. The information that we receive from satellites is invaluable.


"Satellite, Artificial." World Book Encyclopedia CD-ROM. Chicago: World, 1995

Feldman, Anthony. Space. New York: Facts on File, 1980.

Pierce, John. "Types of Artificial Satellites." World Book Encyclopedia, 1993ed.