I will try to answer your question in plane and simple terms. A
satellite is whichever object that rotates around a celestial body,
because of the gravitational attraction. The Moon is the satellite of
the Earth. If the object is artificial (that is man-made) and
artificially injected into its orbit around our planet, then we call
it an "articial satellite". The first artificial satellite was
launched by Soviet Union in 1957 and it was well known Sputnik.
Satellites have two main applications: communications and Earth observation.
As far as the first application is concerned, a satellite is ideal to
relay a radio trasmission from a station on the Earth to another
station (or stations), beyond the natural horizon. So you can connect
together stations that would otherwise not be visible one to the
other.
Satellites are also very useful to take "pictures" of the Earth
surface. These pictures can be used for many applications, both
military and civilian.
Satellites, for instance, take the pictures of the atmosphere used to
predict weather conditions and natural disasters, such as hurricanes.
What is now a "teleport": it is an organized ground station where an
operator, connected to the rest of the world through the terrestrial
backbone network (e.g. optical fibers), conveys information from and
to satellites in its view, using specially dedicated antennas.
The service (and the business) consists in receiving, as a matter of
example, a n audio and video stream from a TV broadcaster and in
up-loading it to a satellite in orbit. This will itself broadcast the
tv signal, at a certain frequency (usually Ku-band, that is 11 GHz)
over a very wide area (e.g. Europe or North America). In other cases,
the satellite services provider sets up a network, based on a
satellite, including a main center (e.g. the HQ's of a corporation)
and a number of local stations, spread over a wide territory.
Please note that the big advantage of satellite communications
networks is that they do not need other infrastructures to work and
that it is relatively easy to establish communications (voice, video
and data) even with very remote and under developed areas of the
world.
Many other things could be said about satellites (e.g. their use for
navigation, as in the GPS system), but I would wait for your reply to
know if this comment was somehow satisfactory. |
