Comsat

Information technology project

Submitted To:Prof. ANITA MISHRA

Submitted By:ALEKHA MITTAL.NIKITA ACHREKAR.RUPALI SHIRSAT

Satellite communications

CONTENTS

SATELLITE COMMUNICATION

INTRO

Basic Elements

ORBITS

WORKINGADVT

DISADVT

SATELLITE

A satellite is an object that orbits another object (known as it primary). The term is often used to describe an artificial satellite(as opposed to natural satellites, or moons).All masses that are part of the solar system, including the Earth, are satellites of the Sun, or satellites of those objects, such as the Moon.The first artificial satellite was the Soviet Sputnik 1, launched on October 4, 1957.There are about 750 satellite in the space,most of them are used for communication.

SATELLITE COMMUNICATIONS

A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications using radio at microwave frequencies. In other words, 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.

BASIC ELEMENTS

Satellite communications are

comprised of 2 main

components:

The Satellite

The Ground Station.

The earth station

Earth station is the common name for every

installation located on the Earth's surface and intended

for communication with one or more satellites.

Earth stations include all devices and installations for

satellite communications: handheld devices for mobile

satellite telephony.

The term Earth station refers to the collection of

equipment that is needed to perform communications

via satellite: the antenna (often a dish) and the

associated equipment (receiver/decoder, transmitter).

The earth station

THE PARTS IN THE SKY

The two main parts in the sky common

to all satellites are called the payload

and the bus.

Payload: transponders, antennas

Bus: physical platform, remote control

THE PAYLOADS

The payload represents all equipment a

satellite needs to do its job. This can include

antennas, cameras, radar and electronics.

The payload is different for every satellite. For

example, the payload for a weather satellite

includes cameras to take pictures of cloud

formations, while the payload for a

communications satellite includes large antennas

to transmit TV or telephone signals to Earth

THE BUS

The bus is the part of the satellite that carries the payload and all its equipment into space. It is the physical platform that holds all the satellite's parts together and that provides electrical power, navigation, control and propulsion to the spacecraft. The bus also contains equipment that allows the satellite to communicate with Earth, a kind of 'remote control'.

ORBITS

There are three types of satellite

communication orbits:-

G.E.O.(Geostationary Earth Orbit)

L.E.O.(Low Earths Orbit)

M.E.O.(Medium Earths Orbit)

ORBITS L .E . O (LOWER

EARTHS ORBITS):

LEO satellites don’t stay in fixed position relative to the surface, and are only visible for 15 to 20 minutes each pass.

G.E.O (GEOSTATIONARY EARTH ORBITS) :

Objects in Geostationary orbit revolve around the earth at the same speed as the earth rotates. This means GEO satellites remain in the same position relative to

the surface of earth.

M.E.O.(Medium Earths Orbit):-MEO satellites are similar to LEO satellites in functionality.

MEO satellites are visible for much longer periods of time than LEO satellites, usually between 2 to 8 hours

BASICS OF SATELLITE COMMUNICATIONS

How do communication satellite works?

Two Stations on Earth want to communicate through

radio broadcast but are too far away to use

conventional means.

The two stations can use a satellite as a relay station

for their communication

One Earth Station sends a transmission to the

satellite. This is called a Uplink.

The satellite Transponder converts the signal and

sends it down to the second earth station. This is called

a Downlink.

WORKING OF SATELLITE COMMUNICATIONS

Types of satellite

Astronomical Satellites:

Astronomical satellites are satellites used for

observation of distant planets, galaxies, and

other outer space objects.

Communications satellites:

Communication Satellites are artificial

satellites stationed in space for the purposes

of telecommunications systems use low

Earth-orbiting satellites.

Earth observation satellites:

Earth observation satellite are satellites specifically

designed to observe Earth from orbit, similar to

reconnaissance satellites but intended for non-military

uses such as environmental monitoring, meteorology,

map making etc.

Navigation satellites:

Navigation Satellite are satellites which use radio signals

transmitted to enable mobile receivers on the ground to

determine their exact location. The relatively clear line of

sight between the satellites and receivers on the ground,

combined with ever-improving electronics, allows

satellite navigation systems to measure location to

accuracies on the order of a few meters in real time

Weather satellitesWeather satellites are satellites that primarily are used to monitor the weather and/or climate of the Earth.Drag-free satellitesDrag – fee satellites are satellites that offers an environment that is as isolated as possible from the forces of nature. A properly designed drag-free-satellite proof mass is uncoupled from the rest of the Universe to a remarkable degree.

Miniaturized SatellitesMiniaturized satellites are satellites of unusually low weights and small sizes. New classifications are used to categorize these satellites: minisatellite (500-200kg), microsatellite (below100kg), nanosatellite (below 10kg).

APPLICATIONS OF SATCOMRadio & TV broadcasting:a. TV satellites deliver hundreds of television channels every day

throughout the world. These satellites are even used to supply television signals to stations for further distribution to the home, or to exchange signals between television studios.

b. The bandwidth required to transmit multiple programmes at the same time can easily be provided using satellites.

Mobile Satellite telephony: Mobile telephony allows the user to make telephone calls and

to transmit and receive data from wherever he/she is located. Digital cellular mobile telephony such as GSM has become a worldwide standard for mobile communications, but its services lack coverage over areas that are sparsely populated or uninhabited(mountains, jungle, sea), because it is not economically viable or practical for the network operators to build antennas there.

Weather forecastinga. With satellites, forecasters can see weather across the whole

globe: the oceans, continents, and poles. Satellites show cloud formations, large weather events such as hurricanes, and other global weather systems.

b. Recent satellite data is very detailed, even to the point of showing states and counties.

Military Applications :Communications satellites are used for military communications applications, such as Global command & Control systems. Examples of military systems that use communication satellites for eg:  the Defens eSatellite Communications System (DSCS).Scientific Research:Scientific research satellites provide us with meteorological information, land survey data , and other different scientific research applications such as earth science, marine science.

ADVANTAGES

The area coverage through satellite transmission is quit large.

The laying & maintenance of intercontinental cable is difficult

and expensive and this is where the satellite provides

alternative.

Satellites can cover large areas of earth. This is particularly

useful sparsely populated areas.

Satellite Costs are independent of distances.

Quality of signal is independent of distances.

DISADVANTAGES

The high investment cost and insurance cost associated

with significant probability of failure.

Launching satellites into orbit is costly.

There is a larger propagation delay in satellite

communication than in terrestrial communication.

CONCLUSION

Satellites remain the best utilization

used for communications due to their

speed and other advantages.

THANK YOU