Satellite Communications

Timothy Pratt, Jeremy E. Allnutt

• Publisher: Wiley
• Year: 2019
• Print ISBN:
  9781119482178
• eBook ISBN:
  9781119482055
• Edition: 3
• Topic: Physical Sciences
• Subtopic: Mechanics

Extensive revision of the best-selling text on satellite communications — includes new chapters on cubesats, NGSO satellite systems, and Internet access by satellite

There have been many changes in the thirty three years since the first edition of Satellite Communications was published. There has been a complete transition from analog to digital communication systems, withanalog techniques replaced by digital modulation and digital signal processing. While distribution of television programming remains the largest sector of commercial satellite communications, low earth orbit constellations of satellites for Internet access are set to challenge that dominance.

In the third edition, chapters one through three cover topics that are specific to satellites, including orbits, launchers, and spacecraft. Chapters four through seven cover the principles of digital communication systems, radio frequency communications, digital modulation and multiple access techniques, and propagation in the earth's atmosphere, topics that are common to all radio communication systems. Chapters eight through twelve cover applications that include non-geostationary satellite systems, low throughput systems, direct broadcast satellite television, Internet access by satellite, and global navigation satellite systems. The chapter on Internet access by satellite is new to the third edition, and each of the chapters has been extensively revised to include the many changes in the field since the publication of the second edition in 2003. Two appendices have been added that cover digital transmission of analog signals, and antennas.

An invaluable resource for students and professionals alike, this book:

• Focuses on the fundamental theory of satellite communications
• Explains the underlying principles and essential mathematics required to understand the physics and engineering of satellite communications
• Discusses the expansion of satellite communication systems in areas such as direct-broadcast satellite TV, GPS, and internet access
• Introduces the rapidly advancing field of small satellites, referred to as SmallSats or CubeSats
• Provides relevant practice problems based on real-world satellite systems

Satellite Communications is required reading for undergraduate and postgraduate students in satellite communications courses and an authoritative reference for engineers working in communications, systems and networks, and satellite operations and management.

1
Introduction

Two developments in the nineteenth and twentieth century changed the way people lived: the automobile and telecommunications. Prior to the widespread availability of personal automobiles, individuals had to travel on foot, by bicycle, or on horseback. Trains provided faster travel between cities, but most people's lives were centered on their home town and immediate surroundings. A journey of 100 miles was a major expedition for most people, and the easy mobility that we all take for granted in the twenty-first century was unknown. Before the telegraph and telephone came into widespread use, all communication was face to face, or in writing. If you wanted to talk to someone, you had to travel to meet with that person, and travel was slow and arduous. If you wanted to send information, it had to be written down and the papers hand-carried to their destination.

Telecommunication systems have now made it possible to communicate with virtually anyone at any time. Early telegraph and telephone systems used copper wire to carry signals over the earth's surface and across oceans, and high frequency (HF) radio made possible intercontinental telephone links.

The development and installation of optical fibers and optical transmission techniques has greatly increased the capacity of terrestrial and oceanic links. Artificial earth satellites have been used in communications systems for more than 50 years and have become an essential part of the world's telecommunications infrastructure. Satellites allow people to receive hundreds of television channels in their homes, either by receiving direct broadcast satellite television signals, or via cable TV from a satellite distribution center. Virtually all cable TV systems collect their signals from satellites that distribute television programming nationwide. Access to the internet via satellite from areas that are not served by cable is also available, providing many people in rural areas with much faster service than can be achieved over telephone lines.

1.1 Background

The origins of satellite communications can be traced to an article written by Arthur C. Clarke in the British radio magazine Wireless World in 1945 (Clarke 1945). At the time, Clarke was serving in the British Royal Air Force, working on precision approach radar systems that could guide World War II aircraft to a safe landing when the airport was fogged in. He was interested in long distance radio communication and was among the first to propose a practical way to communicate using satellites. He later became famous as the author of 2001: A Space Odyssey, and other science fiction books (Clarke 1968). In 1945, HF radio was the only available method for radio communication over transcontinental distances, and it was not at all reliable. Sun spots and ionospheric disturbances could disrupt HF radio links for days at a time. Telegraph cables had been laid across the oceans as early as the mid-1800s, but cables capable of carrying voice signals across the Atlantic did not begin service until 1953. Clarke suggested that a radio relay satellite in an equatorial orbit with a period of one sidereal day would remain stationary with respect to the earth's surface and make possible long distance radio links. (A sidereal day is the time it takes for the earth to make one complete revolution on its axis. It is 3 minutes 55.91 seconds shorter than a clock day of 24 hours, accounting for the progress of the earth around the sun in 365 days, which adds one additional revolution.)

Clarke's Wireless World paper is available on the internet and makes fascinating reading (Clarke 1945). Solar arrays had not been developed in 1945, so Clarke proposed a solar collector driving a steam engine to generate electrical power; a manned space station was needed to run the complicated systems. In most other respects, Clarke accurately predicted the development of geostationary earth orbit (GEO) satellites for direct broadcast television and data communications using transmitter powers much lower than the kilowatt levels of terrestrial broadcasting, and small parabolic mirrors (dishes) for receiving terminals.

At the time Clarke wrote his paper there were no satellites in orbit nor rockets powerful enough to launch them. But his ideas for what we now know as a geostationary satellite system were not science fiction, as the launch of the Russian satellite Sputnik in 1957 and subsequent GEO satellites was to prove. In 1965 the first geostationary communications satellite, Early Bird, began to provide telephone service across the Atlantic Ocean, fulfilling Clarke's vision of 20 years earlier. Intelsat launched a series of satellites between 1967 and 1969 that provided coverage of the Atlantic, Pacific, and Indian ocean regions, making worldwide coverage by GEO satellite possible, just in time for the Apollo 11 mission that first sent humans to the moon.

Satellite communication systems were originally developed to provide long distance telephone service. In the late 1960s, launch vehicles had been developed that could place a 500 kg satellite in geostationary earth orbit, with a capacity of 5000 telephone circuits, marking the start of an era of expansion for telecommunication satellites. Geostationary satellites were soon carrying transoceanic and transcontinental telephone calls. For the first time, live television links could be established across the Atlantic and Pacific oceans to carry news and sporting events. From its early beginnings in the 1960s, revenue earned from satellite communication systems has increased at an average of about 5% every year, and was valued at US$260B in 2016. Growth was rapid in the early 2000s, falling to 2% by 2016 (SIA 2017).

By year 2016, there were a total of 1459 active satellites in orbit with over 500 GEO communication satellites serving every part of the globe. Although television accounts for much of the traffic carried by these satellites, international and regional telephony, data transmission, and internet access are also important. In the populated parts of the world, the geostationary orbit is filled with satellites every two or three degrees, operating in almost every available frequency band. The global positioning system (GPS) uses 24 satellites in medium earth orbit (MEO) to provide worldwide navigation data for automobiles, ships, and aircraft. The worldwide revenue from Global Navigation Satellite Systems (GNSS) installations, mainly in automobiles, was US$74B in 2016 (SIA 2017).

Figure 1.1 shows how the 1459 active satellites in orbit in 2016 were divided by application. Direct broadcast satellite television (DBS-TV) and video distribution services were the dominant uses of satellites, while navigation services made a major contribution. The large number of earth observation satellites were mainly cubesats.

Figure 1.1 Distribution of satellites in orbit in 2016 by application. More than 500 satellites were in geostationary orbit. Communications includes DBS-TV, civil, and military links. Earth observation by small satellites increased quickly between 2014 and 2017 with the introduction of cubesats.

Source: Adapted from data in (SIA 2017).

Figure 1.2 shows the distribution of revenues generated by the worldwide satellite industry, divided by application. As in Figure 1.1, DBS-TV and video distribution generate more than half the revenue.

Figure 1.2 Distribution of global revenue earned from all satellite activity in 2016. Direct broadcast satellite television (DBS-TV) and Global Navigation Satellite Systems (GNSS) dominate with US$183B in revenue out of a total of US$261B.

Source: Adapted from data in (SIA 2017).

GEO satellites have grown steadily in mass, size, lifetime, and cost over the years. Some of the largest satellites launched to date are the KH and Lacrosse surveillance satellites of the US National Reconnaissance Office weighing an estimated 13 600 kg (30 000 lb) (KH-11_Kennen 2017). By 2000, commercial telecommunications satellites weighing 6000 kg with lifetimes of 15 years were being launched into geostationary orbit at a typical cost around US$125M for the satellite and launch. These costs did not change greatly over the following 15 years, although larger satellites with much higher capacity, and higher cost, have also been launched since 2011. The revenue earning capacity of a GEO satellite costing US$125M in orbit must exceed US$20M per year for the venture to be profitable, and must compete with optical fibers in carrying voice, data, and video signals. A single optical fiber can carry 10 Gbps at a single wavelength of light, and 100 Gbps by employing multiple wavelengths, a capacity similar to that of the largest GEO satellites, and optical fibers are never laid singly but always in bundles. The latest trans-Pacific optical fiber cable can transport 60 terabits per second using multiple optical fibers and optical wavelengths, equivalent to the capacity of 50 large GEO satellites in 2018 (The Verge 2017). GEO satellites cannot compete with optical fibers for point to point communications, but have the advantage of broadcasting to millions of receiving terminals simultaneously. Any place within the satellite coverage can be served by simply installing an earth terminal. To do the same with a fiber optic link requires fiber to be laid. Fiber optic transmission systems dominate where there is a requirement for high capacity point-to-point links; GEO satellites succeed best when broadcasting.

The high capacity of both optical fibers and satellites, and the steady move of telecommunications traffic from analog signals to digital has lowered the cost of long distance telephone calls and increased enormously the number of circuits available. In 1960, prior to the advent of satellite communications, the United States had 550 overseas telephone circuits. Calls to Europe cost more than US$1.00 per minute at 1960 prices, and had to be placed through an operator, with delays of many hours being common. By 2016, virtually all international calls could be dialed by the end user, and rates to Europe had dropped to below US$0.02 per minute. To put the reduction in the cost of an international telephone call in perspective, we must remember that incomes have risen significantly over this time period. In the 1950s, the average wage in the United States was US$2.10 per hour, so the average worker would have had to work for 30 minutes to pay for a one minute call to Europe. In 2017, the average wage in the United States was US$26.10 per hour, and required less than 10 second's earnings to pay for the same international call. The United States now has hundreds of thousands of overseas telephone circuits, and video links daily carry live news reports from all over the globe. Texts and emails can be sent over the internet anyw...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• Preface
• About the Authors
• 1 Introduction
• 2 Orbital Mechanics and Launchers
• 3 Satellites
• 4 Satellite Link Design
• 5 Digital Transmission and Error Control
• 6 Modulation and Multiple Access
• 7 Propagation Effects and Their Impact on Satellite-Earth Links
• 8 Low Throughput Systems and Small Satellites
• 9 NGSO Satellite Systems
• 10 Direct Broadcast Satellite Television and Radio
• 11 Satellite Internet
• 12 Satellite Navigation and the Global Positioning System
• Glossary
• Appendix A Decibels in Communications Engineering
• Appendix B Antennas
• Appendix C Complementary Error Function erfc(x) and Q Function Q(z)
• Appendix D Digital Transmission of Analog Signals
• Index
• End User License Agreement