This document provides an overview of satellite communications. It defines a satellite as a smaller object that revolves around a larger object in space. Satellite communication involves transmitting electromagnetic waves between ground stations and satellites to carry information such as voice, audio, video or data. The document describes how satellites work, the different types of satellites including passive and active satellites, and the key elements and services of satellite communication systems. It also discusses the various orbits that satellites can operate in, as well as applications and advantages/disadvantages of satellite communication.

1. SATELLITECOMMUNICATIONS

2. CONTENTS
 Introduction
Defination of Satellite
Need of Satellite Communication
How a Satellite works
Types of Satellites
Basic Satellites
First Satellite in INDIA
Satellite Communication in INDIA
Earth Orbit Satellites
Types of Earth Orbit Satellites
Elements of Satellite Communication
Satellite Communication Services
Advantages and Disadvantages
Applications
Conclusion

3. INTRODUCTION
• The never ending quest of communication engineer is to transmit maximum
information in short time to the largest possible distance, this gave raise to many
systems of communications.
• A satellite is a smaller object that revolves around a larger object in space. For
example, moon is a natural satellite of earth.
• We know that Communication refers to the exchange (sharing) of information
between two or more entities, through any medium or channel. In other words, it is
nothing but sending, receiving and processing of information.
• If the communication takes place between any two earth stations through a satellite,
then it is called as satellite communication. In this communication, electromagnetic
waves are used as carrier signals. These signals carry the information such as voice,
audio, video or any other data between ground and space and vice-versa.

4. Defination of Satellite
• Satellite can be defined as
a heavy object which goes
around object in space due
to the effect of mutual
gravitational forces, used
for broadband
communication.

5. Need of Satellite Communication
• When using a satellite for long
distance communications, the
satellite acts as a repeater.
• An earth station transmits the
signal up to the satellite(uplink),
which in turn retransmits it to
receiving earth station(downlink).
• Different frequencies are used for
uplink/downlink.
• Satellite systems offer more
flexibility than submarine cables,
buried underground cables, line-of-
sight microwave radio or optical
fiber systems.

6. How a Satellite works
• A satellite is a body that moves around another body in a particular path. A communication
satellite is nothing but a microwave repeater station in space.
• A repeater is a circuit, which increases the strength of the received signal and then transmits it.
But, this repeater works as a transponder. That means, it changes the frequency band of the
transmitted signal from the received one.
• The frequency with which, the signal is sent into the space is called as Uplink frequency.
Similarly, the frequency with which, the signal is sent by the transponder is called as Downlink
frequency.
• The transmission of signal from first earth station to satellite through a channel is called as uplink.
Similarly, the transmission of signal from satellite to second earth station through a channel is
called as downlink.
• The process of satellite communication begins at an earth station. Here, an installation is designed
to transmit and receive signals from a satellite in an orbit around the earth. Earth stations send the
information to satellites in the form of high powered, high frequency (GHz range) signals.
• The satellites receive and retransmit the signals back to earth where they are received by other
earth stations in the coverage area of the satellite.
•

7. Types of Satellites
• Satellite communication uses two types of artificial satellites to transmit the signals:
• Passive Satellites: If you put a hydrogen balloon that has a metallic coating over it,
up in the air, it technically becomes a passive satellite. Such a balloon can reflect
microwaves signals from one place to another. The passive satellites in space are
similar. These satellites just reflect the signal back towards the Earth without
amplification. Since the satellite orbit height can range from 2000 to 35786 km,
attenuation due to the atmosphere also comes into play and due to this, the received
signal is often very weak.
• Active Satellites: Active Satellites, unlike passive satellites, amplify the transmitted
signals before re-transmitting it back to Earth, ensuring excellent signal strength.
• Passive satellites were the earliest communication satellite but now almost all the
new ones are active satellites.

8. Basic Satellites
Oct. 4, 1957
The first artificial satellite
was Sputnik, a Russian
beach-ball-size space probe
that lifted off on Oct. 4, 1957.
Telstar
NASA launched Telstar in
June 1962, the world's first
active communications
satellite, into low-Earth orbit.
Project Echo was the first
passive communications
satellite experiment. Each of the two
American spacecraft, launched in
1960 and 1964, were metalized
balloon satellites acting as passive
reflectors of microwave signals.

9. First Satellite In INDIA
ARYABHATA SPACECRAFT
• The Aryabhata spacecraft, named after
the famous Indian astronomer, was
India's first satellite; it was completely
designed and fabricated in India and
launched by a Soviet Kosmos-3M rocket
from Kapustin Yar on April 19, 1975.
• Aryabhata was built by
the Indian Space Research Organization
(ISRO) to conduct experiments in X-ray
astronomy, aeronomics, and solar
physics.
• The satellite weighed 360 kilograms.

10. Satellite Communications in INDIA
• It’s interesting to know that the Indian
National Satellite (INSAT) system is one of
the largest domestic communication
systems that is placed in the geo-stational
orbit. There are more than 200 transponders
in the INSAT system and are used for
various purposes such as
telecommunications, weather forecasting,
television broadcasting, disaster warning,
search and rescue operations, and satellite
newsgathering.
Satellite name Launch date Application
GSAT-30 Jan 17, 2020 Communication
GSAT-31 Feb 06, 2020 Communication
GSAT-15 Nov 11, 2015
Communication
and navigation
GSAT-10 Sep 29, 2012
Communication
and navigation
INSAT-3A Apr 10, 2003
Communication
and climate and
environment
KALPANA-1 Sep 12, 2002
Communication
and climate and
environment
List of Communication satellites along with their
applications:

11. Earth Orbit Satellites
• Satellite should be properly placed in the corresponding orbit after leaving it in
the space. It revolves in a particular way and serves its purpose for scientific,
military or commercial. The orbits, which are assigned to satellites with respect
to earth are called as Earth Orbits. The satellites present in those orbits are
called as Earth Orbit Satellites.
• We should choose an orbit properly for a satellite based on the requirement. For
example, if the satellite is placed in lower orbit, then it takes less time to travel
around the earth and there will be better resolution in an onboard camera.
Similarly, if the satellite is placed in higher orbit, then it takes more time to
travel around the earth and it covers more earth’s surface at one time.
• Following are the three important types of Earth Orbit satellites −
 Geosynchronous Earth Orbit Satellites
 Medium Earth Orbit Satellites
 Low Earth Orbit Satellites

12. Types of Earth Orbit Satellites
GEO MEO LEO
These are very far from the earth. These are little far from earth. These are much closer to earth.
These are placed at the height of
35,786km from the earth surface.
These are placed at the height
in between 8000 km to 18000
km from the earth surface
These are placed at the height
in between 500 to 1500 km from
the earth surface.
Here satellite revolves with same
angular velocity as the earth
rotation.
In this orbit satellite revolves
faster than earth.
LEO satellites don’t stay in
fixed position relative to the
surface.
Maximum time taken to
complete one revolution is
around 23H:56M:4S.
MEO satellites are visible for
particular period of time,
usually between 2 to 8 hours.
These are only visible for 15 to
20 minutes each pass.
Larger coverage area, a single
satellite can cover 42% of earth.
Not as much as GEO satellite. Not as much as GEO, MEO
satellites.
It has larger delay compared to
other orbits.
Delay is less compared to GEO
orbit.
Delay is lesser than GEO and
MEO orbits.

13. Elements of Satellite Communications
• Two major elements of Satellite Communication are
1. Ground segment
2. Space segment
GROUND SEGMENT:
 It is a network of earth stations and user terminals that provides applications
and services to end users.
SPACE SEGMENT:
 Satellite itself is known as space segment and comprised of complex structure.
It has major subsystem like TTC system, Transponder, Fuel Tank called
thrusters tank Antenna and Control system etc.

14. Satellite Communication Services
• One-way satellite communication
• In one-way satellite communication, the communication
usually takes place between either one or multiple earth
stations through the help of a satellite.
• The communication takes place between the transmitter on
the first earth satellite to the receiver which is the second
earth satellite. The transmission of the signal is
unidirectional.
There are two categories in which
the satellite communication
services can be classified:
•One-way satellite communication
•Two- way satellite communication

15. Satellite Communication Services
Two-way Satellite Communication
• In two-way satellite communication, the
information is exchanged between any two earth
stations. It can be said that there is a point to
point connectivity.
• The signal is transmitted from the first earth
station to the second earth station such that
there are two uplinks and two downlinks
happening between the earth stations and the
satellite.

16. ADVANTAGES AND DISADVANTAGES
ADVANTAGES:
• Area of coverage is more than that of terrestrial systems
• Each and every corner of the earth can be covered
• Transmission cost is independent of coverage area
• More bandwidth and broadcasting possibilities
DISADVANTAGES:
• Launching of satellites into orbits is a costly process.
• Propagation delay of satellite systems is more than that of conventional terrestrial systems.
• Difficult to provide repairing activities if any problem occurs in a satellite system.
• Free space loss is more
• There can be congestion of frequencies.

17. APPLICATIONS
• Radio broadcasting and voice communications
• TV broadcasting such as Direct To Home (DTH)
• Internet applications such as providing Internet connection for
data transfer, GPS applications, Internet surfing, etc.
• Military applications and navigations
• Remote sensing applications
• Weather condition monitoring & Forecasting

18. Conclusion
• Satellite Communication technologies have achieved remarkable
breakthrough efficiencies and increase in performance.
• Satellite Communications have the ability to rapidly communicate
between a number of widely dispersed locations.
• Satellites remain the best utilization used for communications due to
their speed and other advantages.