A
communications satellite is an artificial satellite that relays and amplifies
radio telecommunications signals via a transponder; it creates a communication
channel between a source transmitter and a receiver at different locations on
Earth. A communications satellite is an artificial satellite that relays and
amplifies radio telecommunications signals via a transponder; it creates a
communication channel between a source transmitter and a receiver at different
locations on Earth. Communications satellites are used for television,
telephone, radio, internet, and military applications. There are over 2,000
communications satellites in Earth’s orbit, used by both private and government
organizations.
What
is Satellite Communication?
In
satellite communication, signal transferring between the sender and receiver is
done with the help of satellite. In this process, the signal which is basically
a beam of modulated microwaves is sent towards the satellite. Then the
satellite amplifies the signal and sent it back to the receiver’s antenna
present on the earth’s surface. So, all the signal transferring is happening in
space. Thus this type of communication is known as space communication.
Two
satellites which are commonly used in satellite communication are Active and
passive satellites.
Passive
satellites: It is just a plastic balloon having a metal coated
over it. This sphere reflects the coming microwave signals coming from one part
of the earth to other part. This is also known as passive sphere. Our earth
also has a passive satellite i.e. moon.
Active
satellites: It basically does the work of amplifying the
microwave signals coming. In active satellites an antenna system, transmitter,
power supply and a receiver is used. These satellites are also called as
transponders. The transmitters fitted on the earth generate the microwaves.
These rays are received by the transponders attached to the satellite. Then
after amplifying, these signals are transmitted back to earth. This sending can
be done at the same time or after some delay. These amplified signals are
stored in the memory of the satellites, when earth properly faces the
satellite. Then the satellite starts sending the signals to earth. Some active
satellites also have programming and recording features. Then these recording
can be easily played and watched. The first active satellite was launched by
Russia in 1957. The signals coming from the satellite when reach the earth, are
of very low intensity. Their amplification is done by the receivers themselves.
After amplification these become available for further use.
Microwave
communication is possible only if the position of satellite becomes stationary
with respect to the position of earth. So, these types of satellites are known
as geostationary satellites.
What
are the requirements for a satellite to be geostationary?
1. Its revolutionary direction must be
same as that of the earth, i.e. from west to east.
2. The time period of satellite’s
revolution must be same to the time period of the rotation of earth along its
polar axis, which is equal to 24 hours.
3. The equatorial plane of earth must be
coplanar with the orbital plane of the satellites revolution.
The
name given to the orbit of the geo-stationary satellites is synchronous orbit.
Due to this geo-stationary satellites are also called as geo-synchronous
satellites. Geo-synchronous orbit is at a height of nearly 36000km from the
surface of earth.
These
orbits are capable of giving a successful communication link between two
stations present on the earth. These satellites can handle communication up to
large distances. But it is impossible for a single geo-stationary satellite to
cover the whole earth and provide a communication link. Due to curvature of
earth the stations will be out of sight after covering some distance. If we
want to cover the whole earth then we have to put three satellites onto the
geosynchronous orbit. These satellites can cover the earth if all are inclined
at an angle of 120o to each other.
A
geosynchronous satellite is a satellite in geosynchronous orbit, with an
orbital period the same as the Earth's rotation period. Such a satellite
returns to the same position in the sky after each sidereal day, and over the
course of a day traces out a path in the sky that is typically some form of anal
Emma. A special case of geosynchronous satellite is the geostationary
satellite, which has a geostationary orbit – a circular geosynchronous orbit
directly above the Earth's equator. Another type of geosynchronous orbit used
by satellites is the Tundra elliptical orbit.
Geosynchronous
satellites have the advantage of remaining permanently in the same area of the
sky, as viewed from a particular location on Earth, and so permanently within
view of a given ground station
Artificial satellites are human-built objects orbiting the Earth and other
planets in the Solar System. This is different from the natural satellites, or
moons. A satellite is an object that orbits another
object. In space, satellites may be made by man, or they
may be natural. The moon is a natural satellite that orbits the Earth.
Most man-made satellites also orbit the Earth, but some orbit other planets,
such as Saturn, Venus or Mars,
or the moon.
Satellites are used for many purposes. There are weather satellites, communications satellites, reconnaissance satellites, astronomy satellites
and many other kids and stupid idiots.
