•What is satellite?
•History of satellites.
•Types of satellites:
Basing on working:
Basing on type of orbit:
•Applications of satellites
•Limitations in using satellite
What is a satellite?
In general,a satellite is anything that orbits something
else,as,for example:the moon orbits the earth.
In a communication context, a satellite is a
specialized wireless receiver/transmitter that is
launched by a rocket and placed in orbit around the
The path a satellite follows is an orbit.
The velocity required for a satellite to move in an orbit
is termed as orbital velocity.
The velocity required for a satellite to flee away from
the earth is called as escape velocity.
•How does a satellite stay in an orbit?
HOW DOES A SATELLITE WORK?
Consider the light bulb example:
HISTORY OF SATELLITES
Satellite technology has progressed
tremendously over the last 50 years since
Arthur C.Clarke first proposed its idea in 1945
in his article in wireless World.
The first active satellite was launched by
Russia in 1957
The first Indian satellite- Aryabhatta satellite
was launched in 1975.
TYPES OF SATELLITES
Basing on function:
• Passive satellite
• Active satellite
•it is just a plastic balloon having a metal coated
•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.
TYPES OF SATELLITES
It basically does the work of amplifying the microwave
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
These rays are received by the transponders attached to the
Then after amplifying, these signals are transmitted back to
This sending can be done at the same time or after some
The first active satellite was launched by Russia in 1957
TYPES OF SATELLITE( cont.)
Basing on type of orbit:
GEO STATIONARY EARTH ORBIT( GEO )
LOW EARTH ORBIT ( LEO )
MEDIUM EARTH ORBIT ( MEO )
GEO: GEO STATIONARY EARTH ORBIT
These satellites are in orbit 35,863 km above the
earth’s surface along the equator.
It is also termed as geo-synchronous earth orbit.
What are the requirements for a satellite to be
Its revolutionary direction must be same as that of
the earth, i.e. from west to east.
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.
The equatorial plane of earth must be coplanar with
the orbital plane of the satellites revolution.
A GEO satellite’s distance from earth gives it a
large coverage area, almost a fourth of the earth’s
GEO satellites have a 24 hour view of a particular
Its distance from the earth may cause the signal
a single GEO-satellite can cover only 40%of earth’s
surface,due to the curvature of earth.
So 3 geo satellites placed at 120 to each other are
used to cover the entire civilized World.
LEO: LOW EARTH ORBIT
LEO satellites are much closer to the earth than GEO
satellites, ranging from 500 to 1,500 km above the
LEO satellites don’t stay in fixed position relative to
the surface, and are only visible for 15 to 20 minutes
A network of LEO satellites is necessary for LEO
satellites to be useful.
A LEO satellite’s proximity to earth compared to
a GEO satellite gives it a better signal strength
and less of a time delay, which makes it better
for point to point communication.
A network of LEO satellites is needed, which can be
Atmospheric drag effects LEO satellites, causing
gradual orbital deterioration.
MEO: MEDIUM EARTH ORBIT
A MEO satellite is in orbit somewhere between 8,000
km and 18,000 km above the earth’s surface.
MEO satellites are similar to LEO satellites in
MEO satellites are visible for much longer periods of
time than LEO satellites, usually between 2 to 8 hours.
MEO satellites have a larger coverage area than LEO
MEO satellites are visible for longer duration than LEO
MEO satellites are hence required in smaller number
than LEO satellites.
A MEO satellite’s distance gives it a longer time delay
MEO Satellite gives a weaker signal than a LEO
satellite, though not as bad as a GEO satellite
S.NO TYPE OF THE ORBIT DETAILS ADVANTAGES DISADVANTAGES
1. GEOSTATIONARY HEIGHT:35,863KM. LARGE COVERAGE SIGNAL
EARTH ORBIT TIMEPERIOD: 24 HOURS. AREA (ALMOST 4 TH) DELAY
24 HOUR VIEW OF 3GEO
2. LOW EARTH ORBIT HEIGHT:500-1500KM. BETTER SIGNAL AN
TIMEPERIOD:15-20 MIN. STRENGTH. EXPENSIVE
LESS TIME DELAY. NETWORK.
3. MEDIUM EARTH HEIGHT:8000-18000KM. LONGER VISIBILITY. DISTANT-
ORBIT TIMEPERIOD:2-8 HOURS. LESS NUMBER ENOUGH TIME DELAY.
Applications of satellite:
used for long distance communication
high speed data transmission
many receiver stations can receive signal from the
same sender station
are used for detecting where nuclear weapons are
take pictures to help predict the weather
used for GPS(global positioning system) and for
guiding ships and airplanes
Mobile communication-what we are all using right now.
For research and developments in the field of
Navigation and Security
Applications of satellites
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 broadcasts
it another frequency to avoid interference.
So, all the signal transferring is happening in space.
Thus this type of communication is known as space
The first satellite with radio transmitter was in 1957.
The major limitations in using satellites:
It’s initial cost as well as maintenance is
as it is at a very large distance from earth’s
surface there is a scope of signal delay.
IMPOSSIBILITY TO REPAIR AND MAINTAIN:
if any components fail to work there is no
scope of repair.
That is how various types of satellites help
us meet our requirements……
Without our satellites, our great
technological age would be brought to a
In further decades the applications of
satellites in different fields will be more
HOW TO REDUCE