Satellites - Receiving and Collecting Information
Louisa D. / Physics 337/ May 18, 1997
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.
Communication:
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.
Conclusion:
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.
Bibliography
"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.