This document provides an overview of satellite communication systems. It discusses the history of satellites beginning in 1945 and describes various satellite types including GEO, LEO, MEO and HEO. Applications of satellite systems include weather forecasting, radio/TV broadcasting, navigation, telephone networks, and providing remote/rural connectivity. The document also outlines characteristics of satellite systems such as orbital heights, footprints, and specialized antennas.

1. CITY UNIVERSITY
Course Title: Computer Networks
Course Code: CSE317
Topics Name: Satellite
Submitted By:
Afsana Akther Rubi
ID No: 1834902553
Batch: 49th
Submitted To:
Pranab Bandhu Nath
Senior Lecturer
Department of CSE
City University

2. Introduction to Satellite Systems
o A satellite is an artificial object which is placed intentionally into an orbit of any natural
satellite. Satellites are used for many purposes i.e. weather forecasting, digital
transmission, scientific research and development etc.
o In a communication context, a satellite is a specialized wireless transmitter/receiver that
is launched by a rocket and placed in orbit around the earth.
o A satellite can be natural, like the moon, or artificial (human made). So we can say that a
satellite is an object that moves in a curved path around a planet.
History of Satellite Systems
Year Description
1945 Arthur C. Clarke publishes an essay titled "Extra Terrestrial Relays"
1957 First satellite, SPUTNIK
1960 First Reflecting communication satellite, ECHO
1963 First Geostationary satellite, SYNCOM
1965 First Commercial geostationary satellite, "Early Bird" (INTEKSAT I): 240 duplex
telephone channels or 1 TV channel, 1.5 year lifetime.
1976 Three MARISAT satellites for maritime communication.
1982 First mobile satellite telephone system, INMARSAT - A
1988 First satellite system for mobile phones and data communication, INMARSAT -C
1993 First digital satellite telephone system
1998 Global satellite systems for small mobile phones.

3. Characteristics of Satellite Systems
o Satellites have been launched for various applications and are placed at different
altitudes. Moreover their weights are also dissimilar.
o Provides connections between the Earth-based base station and the satellites.
o The GEO satellites, which are at an altitude of 35,768 km, orbit in the equatorial plane
with zero degree inclination and complete exactly one rotation in a day.
o LEO satellite are divided into little and big satellites.
o Little LEOs are smaller in size and are in the frequency range of 148 to 150.
o Several satellites are needed to ensure global coverage. The same frequency spectrum is
also used by MEO and GEO.
o In MEO systems, the slow- moving satellites orbit at a height of about 5,000 to 12,000
km above the earth and have a latency of about 70to 80 ms.
o Specialized antennas are used to provide smaller footprints and higher transmitting
power.
Applications of Satellite Systems
Traditionally, satellites have been used in the following areas:
Weather forecasting
Without the help of satellites, we cannot predict weather. Satellites have the biggest contribution
to making predictions about weather changes by studying the several global scenarios.
Several satellites deliver pictures of the earth using infrared or visible light.
Radio and TV broadcast satellites
Hundreds of TV and radio programs are available via satellites. This technology uses cable in
many places, as it is cheaper to install and, in most cases, no extra fees have to be paid for this
service. Today's satellite dishes have diameters of 30-40 cm in central Europe, and the diameters
in northern countries are slightly larger.
Military satellites
One of the oldest applications of satellites was their use for carrying out espionage. Most of the
communication links are managed via satellite because they are much safer from attack by
enemies.

4. Satellites for Navigation
Even though it was only used for military purposes in the beginning, the GPS (Global
Positioning System) is nowadays well known and available for everyone.
Al our navigation system, Google maps etc. allows for precise localization worldwide, and with
some additional techniques, the precision is in the range of some meters.
There are following applications of satellites in the context of communication:-
Global telephone backbones
One of the first applications of satellites for communication was the establishment of
international telephone backbones. Instead of using cables, it was sometimes faster to launch a
new satellite. These satellites are being replaced by fiber optical cables crossing the oceans.
Connections for remote or developing areas
Due to their geographical location many places all over the world do not have direct connection
to the telephone network or the internet. Satellites now offer a quick and simple connection to
global networks.
Types of Satellite Systems
Four different types of satellites orbits have been identified. These are:

5. o GEO (Geostationary Earth Orbit) at about 36,000km above the earth's surface.
o LEO (Low Earth Orbit) at about 500-1500km above the earth's surface.
o MEO (Medium Earth Orbit) or ICO (Intermediate Circular Orbit) at about 6000-
20,000 km above the earth's surface.
o HEO (Highly Elliptical Orbit)
1. GEO (Geostationary Earth Orbit)
o If a satellite should appear in fixed in the sky, it requires a period of 24 hours. Using the
equation of distance earth and satellite, r = (g.r2 /2.r.f)2)1/3 and the period of 24 hours f =
1/24 h. the resulting distance is 35,786 km. the orbit must have an inclination of 0
degree.
o Geostationary satellites have a distance of almost 36,000 km to the earth. Examples are
almost all TV and radio broadcast satellites, any weather satellites and satellites operating
as backbones for the telephone network.
o Objects in GEO moves around the earth at the same speed as the earth rotates. This
means geostationary satellites remain in the same position relative to the surface of earth.
2. LEO (Low Earth Orbit)
o As LEOs circulate on a lower orbit, it is obvious that they exhibit a much shorter period
(the typical duration of LEO periods are 95 to 120 minutes). Additionally, LEO systems
try to ensure a high elevation for every spot on earth to provide a high quality
communication link.
o Each LEO satellite will only be visible from the earth for about ten minutes.
3. MEO (Medium Earth Orbit)
o A MEO satellite situates in orbit somewhere between 6,000 km to 20,000 km above the
earth's surface.
o MEO satellites are similar to LEO satellites in the context of functionality.
o MEO satellites are similar to LEO satellite in functionality.

6. o Medium earth orbit satellites are visible for much longer periods of time than LEO
satellites usually between 2 to 8 hours.
4. HEO (High Earth Orbit)
o The High Earth orbit satellite is the only non-circular orbit of the four types.
o HEO satellite operates with an elliptical orbit, with a maximum altitude (apogee) similar
to GEO, and a minimum altitude (perigee) similar to the LEO.