Satellite Communication

ABSTRACT

A satellite is defined as a natural space body orbiting around the other natural space body. As for example, moon is the satellite of earth and earth is the satellite of sun. Nowadays the artificial spacecrafts are named satellites as well, because they are launched by a rocket to the space and are kept there by gravitational force revolving around the earth similarly as planets can orbit around the other planets. Satellites are highly specialized wireless receivers/transmitters, which main function is to relay the radio frequency waves and the encoded information in them from one corner of the world to another. The main aim of this work is to discuss satellite communication in details.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• PROBLEM STATEMENT
• AIM AND OBJECTIVE OF THE PROJECT
• ADVANTAGES OF SATELLITE COMMUNICATION
• DISADVANTAGES OF SATELLITE COMMUNICATION
• APPLICATIONS OF SATELLITE COMMUNICATION
• PROBLEM OF SATELLITE COMMUNICATION

CHAPTER TWO

LITERATURE REVIEW

• HISTORICAL BACKGROUND OF SATELLITE COMMUNICATION
• EARLY ACTIVE AND PASSIVE SATELLITE EXPERIMENTS
• SATELLITE ORBITS
• SATELLITE COMMUNICATION SERVICES

CHAPTER THREE

• COMPONENTS OF A SATELLITE
• SATELLITE COMMUNICATION BLOCK DIAGRAM
• NEED FOR SATELLITE COMMUNICATION
• WORKING PRINCIPLE OF SATELLITE COMMUNICATIONS
• OPERATION LIMIT OF SATELLITE
• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

Satellite communication is the method of transporting information from one place to another using a communication satellite in orbit around the Earth. Satellite communication, in telecommunications, is the use of artificial satellites to provide communication links between various points on Earth. Satellite communications play a vital role in the global telecommunications system (Labrador, 2016).

Communications satellites are used for television, telephone, radio, internet, and military applications. Most communications satellites are in geostationary orbit 22,236 miles (35,785 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite (Labrador, 2016).

The high frequency radio waves used for telecommunications links travel by line of sight and so are obstructed by the curve of the Earth. The purpose of communications satellites is to relay the signal around the curve of the Earth allowing communication between widely separated geographical points (Asif Siddiqi, 2017). Communications satellites use a wide range of radio and microwave frequencies. To avoid signal interference, international organizations have regulations for which frequency ranges or “bands” certain organizations are allowed to use. This allocation of bands minimizes the risk of signal interference (Arthur C, 2015).

Satellite has the ability to receive signals from Earth and to retransmit those signals back with the use of a transponder—an integrated receiver and transmitter of radio signals. A satellite has to withstand the shock of being accelerated during launch up to the orbital velocity of 28,100 km (17,500 miles) an hour and a hostile space environment where it can be subject to radiation and extreme temperatures for its projected operational life, which can last up to 20 years.

A satellite in geostationary orbit can deviate up to a degree every year from north to south or east to west of its location because of the gravitational pull of the Moon and Sun. A satellite has thrusters that are fired occasionally to make adjustments in its position. The maintenance of a satellite’s orbital position is called “station keeping,” and the corrections made by using the satellite’s thrusters are called “attitude control.” A satellite’s life span is determined by the amount of fuel it has to power these thrusters. Once the fuel runs out, the satellite eventually drifts into space and out of operation, becoming space debris.

A satellite in orbit has to operate continuously over its entire life span. It needs internal power to be able to operate its electronic systems and communications payload. The main source of power is sunlight, which is harnessed by the satellite’s solar panels. A satellite also has batteries on board to provide power when the Sun is blocked by Earth. The batteries are recharged by the excess current generated by the solar panels when there is sunlight.

Satellites operate in extreme temperatures from −150 °C (−238 °F) to 150 °C (300 °F) and may be subject to radiation in space. Satellite components that can be exposed to radiation are shielded with aluminium and other radiation-resistant material. A satellite’s thermal system protects its sensitive electronic and mechanical components and maintains it in its optimum functioning temperature to ensure its continuous operation. A satellite’s thermal system also protects sensitive satellite components from the extreme changes in temperature by activation of cooling mechanisms when it gets too hot or heating systems when it gets too cold.

1.2                                                  PROBLEM STATEMENT

The need for satellite communication becomes evident when we want to transmit the signal to far off places, where the Earth’s curvature comes into play. This obstruction is overcome by putting communication satellites in space to transmit the signals across the curvature.

1.3                                     AIM AND OBJECTIVE OF THE STUDY

Communication satellites are designed to relay several, or more usually many, signals simultaneously. In some cases there may be a separate transponder for each carrier; this is typical of broadcasting satellites and of satellites used for distributing television signals to terrestrial broadcasting stations. The main aim of this work is to discuss satellite communication in details.

1.4                         ADVANTAGES OF SATELLITE COMMUNICATION

The following are the advantages of satellite communication:

• Installments of circuits are easy.
• The elasticity of these circuits is excellent.
• With the help of satellite communication, every corner of the earth can be covered.
• The user fully controls the network.

1.5                      DISADVANTAGES OF SATELLITE COMMUNICATION

The following are the disadvantages of satellite communication:

• Initial expenditure is expensive.
• There are chances of blockage of frequencies.
• Propagation and interference.

1.6                         APPLICATIONS OF SATELLITE COMMUNICATION

• Telephone
• Television
• Digital cinema
• Radio broadcasting
• Amateur radio
• Internet access
• Military
• Disaster Management

1.7                             PROBLEM OF SATELLITE COMMUNICATION

Launching a satellite into space requires a very powerful multistage rocket to propel it into the right orbit. And also, the cost of launching a satellite is quite expensive and based on weight. To meet these challenges, satellites must be small and made of lightweight and durable materials. They must operate at a very high reliability of more than 99.9 percent in the vacuum of space with no prospect of maintenance or repair.