The Evolution of Satellite Communications

views updated

The Evolution of Satellite Communications

Overview

After the Chinese designed the first rockets, they used the "fire arrows" to repel Mongol invaders. Those early defenders would be amazed to discover the hundreds of satellites launched into orbit around Earth using technologies that developed from their invention. With the launch of the first man-made Earth satellite, Sputnik 1, in 1957, the world began considering the vast possibilities to be found in the "space" above the planet's surface. Satellites rapidly evolved from Sputnik's simplistic beeping radio transmitters to the sophisticated communications relay stations orbiting Earth in the 1990s, revolutionizing the way mankind experienced the world.

Background

Around 300 b.c. the Chinese invented gunpowder, which was later packed into bamboo tubes to make a primitive firecracker. By 1232, when the Chinese defended their lands from Mongol invaders during the battle of Kai-Keng, an inventive native had decided to add the firecracker to an arrow, in essence creating the first bottle rocket. Ballistic weapons became commonplace in war, but rocket science didn't really emerge until the turn of the century in America. In the early 1900s American Robert H. Goddard (1882-1945) began experimenting with rocket propulsion—he received his first two U.S. patents in 1914 for a liquid-fueled rocket engine and a two or three-stage solid fuel rocket. In a technical report for the Smithsonian in 1920, Goddard outlined how a rocket might reach the moon, causing an uproar in the scientific community, who labeled him a crackpot. (His report, however, became the foundation for the early rocket program of the German army, which made further advancements in rocket science during the Second World War.) Goddard's rocketry research led to 200 patents, including important advances in liquid fuel and guidance systems. He was the first to launch a scientific payload—in 1929 he sent up a barometer and a camera. Goddard's discoveries paved the way for the modern rocket technology that would launch the first man-made satellites into space.

In October 1945 British physicist (and science fiction author) Arthur C. Clarke (1917- ) published an article in Wireless World that described a system of manned satellites in orbit above Earth that would distribute global communications through a "relay" service. Clarke predicted that these satellites, in orbit above the equator at an altitude of 22,300 miles (36,000 km), would revolve around Earth in 24 hours, appearing motionless from the surface. While Clarke was by no means the first to theorize about a fixed orbit for satellites, his concept had a great influence on their technological development. Future satellite scientists would term Clarke's hypothesis "geostationary" orbit, and the ring 22,300 miles above Earth's surface became known as the "Clarke belt" (also called the "Clarke orbit").

In the decade following the publication of Clarke's article, satellite research was influenced by several significant scientific advancements. The Cold War between America and the Soviet Union brought about long-range, high-powered rocketry, including intercontinental ballistic missiles (ICBMs). The first solar cells were developed; these would eventually be used to power satellites. The invention of the transistor made possible the miniaturized electronic components necessary for lightweight space objects and also ushered in the age of the high-speed digital computer, which would be used to calculate and track satellite orbits. All of these scientific advances served to kick off the race into space. On October 4, 1957, the Soviet Union set an historic landmark with the launch of the first Earth-orbiting satellite, Sputnik 1, a 184-pound sphere about the size of a basketball. It was sent into space as part of the International Geophysical Year (IGY) research project.

Though limited (it only flew for 92 days) in success, Sputnik 1 spurred scientists and engineers to design more sophisticated satellites. In January 1958 the United States managed, after two failed attempts, to launch its first IGY satellite, Explorer 1, which was instrumental in the discovery of Earth's radiation belts. In July 1958 the U.S. Congress passed the National Aeronautics and Space Act, which created the National Aeronautics and Space Administration (NASA) and served to jump-start U.S. space science and exploration. (NASA's first communications satellite, Echo 1, a passive communication device, was launched in August 1960.) Before the end of 1958 the world's first "active" communication satellite, SCORE (Signal Communication by Orbiting Relay Equipment), was launched by the U.S. Air Force. It transmitted a pre-recorded Christmas message from President Dwight D. Eisenhower (1890-1969) and lasted 12 days. Because it did not receive and retransmit a signal from Earth, SCORE was not a truly active communications satellite. In 1960 the U.S. Department of Defense launched Courier, the world's first fully active communications satellite. Courier, also the first solar-powered communications satellite, received and retransmitted signals, but it only functioned for 17 days.

Impact

The proven success of the early satellites stimulated a surge in private sector interest in communications satellites. By 1960 officials with AT&T had filed with the Federal Communications Commission (FCC) for authorization to launch an experimental satellite, catching the U.S. government with no policy in place to govern such requests. As a result, competitive contracts were awarded by NASA to RCA (for a medium orbit active communications satellite), AT&T (for its own medium orbit satellite), and Hughes Aircraft Company (for a high-orbit satellite). In July 1962 NASA launched the world's first private sector communications satellite, AT&T's Telstar, which transmitted the first live transatlantic telecast on July 10. Voice, television, facsimile, and data were transmitted between the U.S. and various sites in Europe. Telstar opened space to commercial users, sparking a communications revolution.

In concert with the private sector, NASA launched Relay 1, built by RCA, in December 1962. Relay was the first satellite deployed with backup systems in case of system failure, and its transmission of telephone and television signals to Europe, South America, and Japan gave the first demonstration of the possibilities of true global communications via satellite. (Because of its low orbit, however, Relay could only provide real-time communications for short periods, a problem that spurred research and development into higher orbiting satellites, looking towards finally realizing Arthur C. Clarke's hypothesis, the geostationary orbit.) NASA turned to their contract with Hughes and, in February 1963, launched Syncom, the first satellite to achieve geosynchronous orbit. Shortly afterward, Syncom suffered electrical equipment failure, and Syncom II was launched to takes its place. By 1964 Syncom III, the most famous satellite in the series, had been launched and used to transmit the Olympic games live from Tokyo.

The success of the NASA-Hughes satellites presaged the most significant event in modern satellite evolution—the launch of the first commercial communications satellite, Early Bird, in April 1965 by Comsat, the Communications Satellite Corporation. Just twenty years shy of the anniversary of Arthur C. Clarke's momentous article on satellite possibilities, global communications satellites became a reality with the launch of Early Bird into geosynchronous orbit over the Atlantic Ocean, providing the first continuous satellite communications link. Its siblings, Intelsat II and III, provided further links to complete the first global network, which in 1969 allowed over one half billion people to watch Apollo 11 land on the Moon on July 20. Such live global telecasts along with international telephone transmissions became the foundation of global satellite communications.

While global communications evolved, domestic satellite systems were also learning from the experiences of the Soviet Union, which had launched the world's first domestic system, called Molniya, in 1965. By the early 1970s both Canada and the United States began to develop domestic satellite networks of their own. In Canada the first North American domestic communications satellite, Anik, was launched in November 1972. The first U.S. domestic communications satellite was Western Union's Westar, launched in April 1974. Early on, the North American satellites were used primarily for long-distance telephone and data communications. Then, in 1975, an American pay TV service announced it would begin using a satellite to provide its broadcasts to cable TV stations nationwide. On September 30, 1975, Home Box Office, Inc., went on the air, delivering live coverage of a world championship boxing match. Very quickly, other services joined HBO in leasing spots onboard satellites, fueling an explosion in the development of thousands of U.S. cable TV systems.

These early commercial satellite applications—international telephone, television, cable television, and data networks—were dwarfed by growth in the industry in the late twentieth century. Beginning in 1976 with the launch of Marisat, the first communications system to provide mobile services (to the U.S. Navy and other maritime customers), global communications grew exponentially as new technologies were introduced. Three of the most significant advances—cellular telephones, direct broadcast satellite television, and the Internet—incited rapid progress in the development of low earth orbit (LEO) satellites. Hundreds of sophisticated LEOs were deployed, providing high-speed digital communications to even the most isolated regions around the world. From Iridium's hand-held global satellite telephones, first activated in November 1998, to the direct broadcast satellite technology of DirecTV, launched in 1994, to the Wireless Web service, introduced to digital telephone customers in 1999, low earth orbiting satellites brought the world closer together.

Satellite technology delivered e-mail, telemedicine, teleschooling, and telecommuting to the masses—from China to the United States to coldest Antarctica—permitting the continuous exchange of video, audio, and data information between distant locations around the earth. In the 1990s the near instant transmission of live news, sports, entertainment, and data brought the whole world to each of its inhabitants. Historic events such as the end of the Cold War (personified by the collapse of the Berlin Wall), the Gulf War, and the conflict in Kosovo were visible on world televisions as they occurred, affecting global opinion as well as the events themselves. From Sputnik in 1957 to the smallest low orbit device spinning out to space in 1999, satellites had changed the way the world lived and worked.

ANN T. MARSDEN

Further Reading

Books

Fthenakis, Emanuel. Manual of Satellite Communications New York: McGraw-Hill, 1984.

Hudson, Heather E. Communication Satellites: Their Development and Impact. New York: The Free Press, 1990.

Long, Mark. 1985 World Satellite Almanac: The CompleteGuide to Satellite Transmission & Technology. Boise, ID: CommTek Publishing Company, 1985.

Martin, James. Communications Satellite Systems. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1978.

Internet Sites

Whalen, David J. "Communications Satellites: Making the Global Village Possible. http://www.hq.nasa.gov/office/pao/History/satcomhistory.html

About this article

The Evolution of Satellite Communications

Updated About encyclopedia.com content Print Article Share Article

NEARBY TERMS

The Evolution of Satellite Communications