Communications Satellite Industry
Communications Satellite Industry
The beginning of the satellite communications era began with the publication of a paper written by Arthur C. Clarke in 1945. The paper described human-tended space stations designed to facilitate communications links for points on Earth. The key to this concept was the placement of space stations in geosynchronous Earth orbit (GEO), a location 35,786 kilometers (22,300 miles) above Earth. Objects in this orbit will revolve about Earth along its equatorial plane at the same rate as the planet rotates. Thus, a satellite or space station in GEO will seem fixed in the sky and will be directly above an observer at the equator. A communications satellite in GEO can "see" about one-third of Earth's surface, so to make global communications possible, three satellites need to be placed in this unique orbit.
Clarke envisioned a space station, rather than a satellite, as a communications outpost because he felt that astronauts would be needed to change vacuum tubes for the receivers and transmitters. However, the concept became extraordinarily complex and expensive when life support, food, and living quarters were factored in. For this reason, and because telephone and television services were perceived as adequate, Clarke's idea was not given much attention. In 1948 the vacuum tube was replaced by longer-lived solid-state transistors, marking the dawn of microelectronics. Humans, it seemed, might not be required to tend space-based communications systems after all. Nonetheless, questions remained: Would there be a demand for communications satellites, and, if so, how would they be placed in orbit?
During the mid-twentieth century, people were generally satisfied with telephone and television service, both of which were transmitted by way of cable and radio towers. However, telephone service overseas was exceptionally bad, and live television could not be received or transmitted over great distances. Properly positioned satellites could provide unobstructed communications for nearly all points on Earth as long as there was a method to put them in orbit.
Shortly after World War II, the United States acquired the expertise of German rocket engineers through a secret mission called Operation Paper-clip. The German rocket program, which produced the world's first true rocket, the V-2,*was highly valuable to the United States. These engineers were sent to New Mexico to work for the army using hundreds of acquired V-2 missiles. Within a decade, the German engineers produced powerfulmissiles called Jupiter, Juno, and Redstone. At the same time, the U.S Air Force was interested in fielding intercontinental ballistic missiles (ICBMs) and was separately developing the Atlas, Thor, and Titan rockets to meet this mission. The navy also had a rocket program and was working on a medium-range missile called Vanguard.
On October 4, 1957, the Soviet Union launched Sputnik I, a satellite whose purpose was to demonstrate Soviet technology. Americans were alarmed and demanded that the government establish a space program to regain prestige. President Dwight Eisenhower, they felt, did not do enough to prevent the United States from lagging behind the Soviets technologically. In truth, Eisenhower had directed the navy to launch a satellite on Vanguard, but the rocket was encountering setbacks. The mission to launch the first American satellite fell to the army, whose Juno instrument was doing remarkably well. The satellite Explorer 1 finally went up on January 31, 1958. Launching satellites was possible, and communications satellite concepts were now seriously being considered.
The First Communications Satellites
On December 18, 1958, the military's Satellite Communications Repeater (SCORE) was launched into low Earth orbit (LEO) by a U.S. Air Force Atlas. SCORE was designed to receive a transmission, record it on tape, and then relay the transmission to another point on Earth within hours. President Eisenhower used the opportunity to demonstrate American technology by transmitting a recorded Christmas greeting to the world, the first time in history a satellite was used for communications.
Recognizing the potential of satellite communications, John Pierce, director of AT&T's Bell Telephone Laboratories, developed projects designed to test various communications satellite concepts. The National Aeronautics and Space Administration (NASA), only two years old, planned to send an inflatable sphere into space for scientific research. Pierce wanted to use the opportunity to reflect signals off the balloon's metallic surface. On August 12, 1960, the sphere, called Echo 1, was successfully launched, and Pierce was encouraged by the reflective signal tests. Because Echo 1 had no electronic hardware, the satellite was described as passive. For communications to be effective, Pierce felt that active satellites were required.
Meanwhile, the military was continuing with the tape-recorded communications concept, developing new satellites called Courier. The first one was destroyed when the rocket exploded. Courier 2 was successfully launched on October 4, 1960, but failed after seventeen days of operation. During this time, significant military resources were being allocated to Atlas, Titan, and intelligence satellites, which took priority.
Two years after the Echo 1 experiments, Bell Laboratories created Telstar, an active communications satellite designed to operate in medium Earth orbit (MEO), about 5,000 kilometers (3,107 miles) above Earth's surface. During this time, NASA selected a satellite design from RCA called Relay to test MEO communications but agreed to launch Telstar as soon as it was ready. Telstar 1 was launched on July 10, 1962, and Relay 1 was sent up on December 13 of the same year. Both were successful, and despite Relay 1's greater sophistication, people remembered Telstar's live television broadcasts from the United States to locations in Europe.
Advantages and Disadvantages.
Soon the advantages and disadvantages regarding LEO and MEO communications satellites were being studied. One problem with communications satellites in orbits lower than geosynchronous is the number of satellites required to sustain uninterrupted transmissions. Whereas a single GEO satellite can cover 34 percent of Earth's surface, individual LEO and MEO satellites cover only between 2 and 20 percent. This means that a fleet of satellites, called a "constellation," is required for a communications network.
The major advantage in using LEO and MEO communications satellites is a minimization of latency, or the time delay between a transmitted signal and a response, often called the "echo effect." Even though transmissions travel at the speed of light, a time delay of 0.24 seconds for a round-trip signal through a GEO satellite can make phone calls problematic. Despite this drawback, sending three communications satellites to GEO would save money, and people would not need to wait years for an LEO or MEO constellation to be complete.
Comsat
Shortly after the Soviet Union launched the first human into space,* President John Kennedy wanted a national plan for space exploration and settled on a series of programs that included the famous Apollo missions to the Moon. Less familiar but perhaps more significant for the long term, Congress, with the support of President Kennedy, authorized the establishment of an organization designed to integrate the nation's space-based communications network.
Formed in February 1963 by the Communications Satellite Act of 1962, the Communications Satellite Corporation, or Comsat, was given the task of creating a national communications satellite system in the earliest possible time. Half of Comsat would be publicly traded, and the other half would be purchased by satellite manufacturers. Comsat's first major hurdle was deciding what kind of satellite system it would pursue: LEO, MEO, or GEO. Because Telstar and Relay were successful, these MEO systems seemed the default choice. For uninterrupted communications service, however, about twenty satellites such as Telstar or Relay were needed, costing an estimated $200 million. The president of Comsat, Joseph Charyk, a veteran of satellite engineering programs, was not sure that this was the right way to proceed.
Meanwhile, Hughes Aircraft Company was developing the Syncom series of satellites, each designed to test communications technologies in GEO. The first two satellites were not entirely successful, but Syncom 3, launched on August 19, 1964, achieved a stationary GEO. Charyk was aware of the Syncom project early on and followed its progress closely. Comsat was beginning to realize that a GEO communications satellite network was the most practical in terms of cost. Nevertheless, Comsat asked a variety of companies to study the feasibility of LEO communications constellations in the event that a GEO system was unsuccessful. AT&T and RCA researched the merits of a random system, in which satellites drifted freely without any particular relationship to one another. STL and ITT studied the phased approach, where strings of satellites orbiting at LEO were spaced in such a way to allow for continuous, uninterrupted communications. Comsat finally decided on a GEO system, and on April 6, 1965, it launched Early Bird. This satellite also became a test bed for the latency problem, and methods to suppress the echo effect were successfully employed.
Bandwidth Capacity
During this time, NASA continued to fund research in communications satellite technology, contributing to programs such as Applications Technology Satellites (ATS). Six ATS units were developed and launched, and each was designed to test various technologies related to bandwidth capacity and new components. Of particular importance was bandwidth capacity, the range of frequencies used in a satellite.
Satellite communications providers were particularly interested in boosting the capacity of transponders used for telephone conversations and television broadcasts. A telephone call, for example, uses about 5 kilohertz of bandwidth. A satellite with 50 kilohertz of bandwidth can handle ten calls simultaneously. Early satellites could only handle about thirty calls at one time and were easily overwhelmed. Research continued to improve the capacity problems, and digital technologies have significantly increased the number of simultaneous calls. Satellite engineers also designed antennas that did not interfere with systems orbiting nearby and recommended adequate separation between satellites to prevent signals from interfering.
Becoming Global
After the establishment of Comsat, efforts were under way to approach the international community about setting up a global communications satellite network. Comsat dispatched several key people, along with U.S. State Department officials, to a dozen nations interested in the communications satellite market. In 1964, Intelsat was formed, and it started operations using part of the new Early Bird satellite launched in 1965. Comprised originally of twelve members, Intelsat is an organization that owns and operates global communications networks providing voice, video, and data services. Intelsat collects investment capital from its members and makes a profit from the sale or lease of satellite services. In 2000, Intelsat had 143 member countries and signatories, with Comsat still representing the United States.
Other international communications satellite organizations have since formed, such as Eutelsat, a cooperative formed in 1977 providing regional communications services for Europe. France, England, and Germany established the European Space Research Organization (ESRO) and the European Launch Development Organization (ELDO) shortly after the launch of an experimental communications satellite called Symphonie in 1967. ESRO was responsible for research, development, construction, and operation of payloads and ELDO handled launch activities. Because of management and system integration concerns, ESRO and ELDO merged to form the European Space Agency in 1974. Three years later, the Conference of European Posts and Telecommunications (CEPT) approved the formation of Eutelsat, which by 2000 had nearly fifty members.
Comsat was also asked to assist in the development of a regional communications satellite organization for southwestern Asia, northern Africa, and areas of southern Asia. Comsat agreed and was contracted to develop and build what later became known as Arabsat. Inmarsat, founded in 1982, is another international organization providing global communications services to seagoing vessels and oil platforms.
The Soviet Union, recognizing the benefits of a global communications satellite network, was not interested in a GEO system because of the country's northern location. A GEO system comprised of three satellites would miss parts of the Soviet Union. The Soviets developed an ingenious solution by launching communications satellites into highly elliptical orbits. The orbit consisted of a very close and fast approach over the Southern Hemisphere while tracing a slow and lengthy arc over the Soviet mainland. In 1965 the Soviet Union launched its first communications satellite as part of an ongoing system called Molniya, a name also assigned to the unusual orbit it occupies.
The Soviet Union, despite being approached by representatives of Comsat and the State Department to join Intelsat, declined membership and initiated a regional network in 1971 called Intersputnik. Intersputnik was successful during the following decades with its Gorizont, Express, and Gals satellites but experienced funding difficulties after the collapse of the Soviet Union in 1991. In the 1990s, however, Intersputnik was revitalized with a membership of twenty-three nations and the recent introduction of a new series of satellites, the Express-A.
Back to LEO?
In the early 1990s, LEO communications satellite constellations were revisited. Microelectronics was allowing for smaller satellites with greater capacities, and the launch industry was stronger than it was thirty years earlier. Two companies that pursued this concept were Iridium and Teledesic.
Iridium's plan was to loft about 100 satellites into several LEOs to provide uninterrupted cell phone and pager services anywhere on Earth. Iridium became the first company to provide these services on November 1, 1998. Sixty-six Iridium satellites, all built by Motorola, were launched in the late 1990s. Unfortunately, Iridium filed for bankruptcy in 1999.*
Despite the anticipated effect of Iridium's 1999 bankruptcy on the market, Teledesic, a company planning to provide computer networking, wireless Internet access, interactive media, and voice and video services, will use LEO satellites developed and built by Motorola. Founded by Craig McCaw and Microsoft founder Bill Gates with $9 billion in 1990, Teledesic also experienced financial troubles but by 2000 was prepared to tap into part of the market originally pursued by Iridium. With Lockheed Martin contracted to provide launch services for all 288 satellites plus spares, Teledesic plans to be operational in 2005.
By 1998 satellite communications services included telephone, television, radio, and data processing, and totaled about $65.9 billion in revenues, or almost 7 percent of the total telecommunications industry. During that year, about 215 communications satellites were in GEO and 187 in LEO.
see also Clarke, Arthur C. (volume 1); Communications, Future Needs in (volume 4); Ground Infrastructure (volume 1); Satellite Industry (volume 1).
Phil Smith
Bibliography
Alper, Joel, and Joseph N. Pelton, eds. The Intelsat Global Satellite System. New York:American Institute of Aeronautics and Astronautics, 1984.
Brown, Martin P., ed. Compendium of Communication and Broadcast Satellites. New York: Institute of Electrical and Electronics Engineers, 1981.
Caprara, Giovanni. The Complete Encyclopedia of Space Satellites. New York: Portland House, 1986.
Clarke, Arthur C. "Extraterrestrial Relays: Can Rocket Stations Give World-wideRadio Coverage?" Wireless World, October (1945):305-308.
Hickman, William. Talking Moons: The Story of Communications Satellites. New York:World Publishing Company, 1970.
Launius, Roger D. NASA: A History of the U.S. Civil Space Program. Malabar, FL:Krieger Publishing, 1994.
McLucas, John L. Space Commerce. Cambridge, MA: Harvard University Press, 1991.
Sellers, Jerry Jon. Understanding Space: An Introduction to Astronautics. New York: Mc-Graw-Hill, 1994.
Walter, William J. Space Age. New York: Random House, 1992.
*In 1944 and 1945, the Nazis launched V-2 ballistic missiles toward England, but the assault came too late to turn the war in Germany's favor.
*On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first human in space, making a one-orbit, ninety-minute flight around Earth.
*In 2000 Iridium Satellite LLC purchased the Iridium satellite system and began selling satellite phone service at much lower prices than its predecessor, Iridium.
Communication Satellites
COMMUNICATION SATELLITES
COMMUNICATION SATELLITES. Artificial communication satellites can relay television, radio, and telephone communication between any two places on the globe and from space to other objects in space or on earth. The military, commercial companies, and amateurs from over twenty nations have hundreds of communication satellites orbiting the earth. This has been accomplished in a mere forty-five years.
The origin of artificial communications satellites began over a century ago with Guglielmo Marconi's electric waves transmission in 1896. The possibilities for satellites improved gradually with advances in short wave communication and radar in the 1930s, and with the possibilities of rocket flight after Robert H. Goddard's rocket demonstration in the 1920s. In 1945, British scientist and science fiction author Arthur C. Clarke published an article in which he predicted the launching of orbital rockets that would relay radio signals to earth. At last, on 4 October 1957, the Soviet Union launched Sputnik I, the first artificial satellite. Clarke's seemingly far-fetched prediction had come true in about ten years. It took over fifty years from the early possibilities to the first satellite, but the next forty-five years saw tremendous and rapid technical advancement and proliferation of worldwide satellite communication.
Early Communication Satellites
The United States entered the Space Age when it launched the Explorer 1 satellite in January 1958. At the end of 1958, an Atlas B rocket launched a SCORE communications satellite, which contained two radio receivers, two transmitters, and two tape recorders. It broadcast a taped Christmas greeting from President Dwight D. Eisenhower. Then, in August 1960, the National Aeronautics and Space Administration (NASA) launched Echo 1, a giant, ten-story Mylar balloon reflector that relayed voice signals. It was so bright it could be seen by the naked eye. Echo 1 launched the American satellite communication era.
At that time, there were two principal viewpoints toward satellite relay. One side favored the Echo passive satellite system, artificial "moons" that would reflect electromagnetic energy. The other view favored active satellites, which would carry their own equipment for reception and transmission. Courier 1B, launched in October 1960 shortly after Echo 1, was the first active transmitter and used solar cells and not chemical batteries for power. Telstar 1, the first commercial satellite, was built by AT&T and launched by NASA in 1962. It provided direct television transmission between the United States and Japan and Europe and proved the superiority of active satellite communication, as well as the capability of commercial satellites (COMSATS) to provide multi channel, wideband transmission.
Satellites receive signals from a ground station, amplify them, and then transmit them at a different frequency to another station. Most ground stations have huge antennas to receive transmissions. Smaller antennas than used in years past have been placed closer to the user, such as on top of a building. By using frequencies allocated solely to a satellite, rather than going through the earth microwave stations, communications are much faster. This allows for teleconferencing and for computer to computer communications.
International Communications
In 1962, President John F. Kennedy signed legislation to create the Communications Satellite Corporation to represent the United States in a worldwide satellite system. In 1964, under United Nations auspices, the International Telecommunications Satellite Consortium (Intelsat) was formed. From then on, communication satellites had synchronous, high-altitude, elliptical orbits, which improved communications. The Intelsat 1 (Early Bird) was launched in 1965 for transatlantic communication service. It could transmit 240 simultaneous telephone calls or one color television channel between North America and Europe.
By 1970, the Intelsat 4s provided 4,000 voice circuits each; by 1990, each satellite could carry over 24,000 circuits. As of 2002, there were 19 Intelsats in orbit, as well as many other competing satellite communications systems in the United States and Europe. Intelsats can communicate with each other and with other satellite systems as well. For instance, Intelsats and the Russian satellites provide the hotline between Washington, D.C., and Moscow.
Development in communication satellites systems results from many sources. The first ham, or amateur, radio satellites were launched in 1961. By 1991, thirty-nine amateur communications satellites had been launched, many sent free as ballast on government rockets. As of 2002, there were six countries that owned their own communications satellites for domestic telephone service and some twenty-four countries that leased from the Intelsat systems for domestic service. Commercial satellites have been developed by some twenty countries and provide many communications services. Television programs can be transmitted internationally by beaming off satellites. Satellites also relay programs to cable television systems and homes equipped with dish antennas, until recently only a possibility for sophisticated military use.
New Technology
One new technique of the 1990s is called frequency reuse, which expands the capabilities of satellites in several ways. It allows satellites to communicate with a number of ground stations using the same frequency. The beam widths can be adjusted to cover different-sized areas—from as large as the United States to as small as a single small state. Additionally, two stations far enough apart can receive different messages transmitted on the same frequency. Also, satellite antennas have been designed to transmit several beams of different sizes in different directions.
The satellite communications systems of NASA, called Tracking and Data Relay Satellites (TDRS), which began in 1983, provide links between space shuttles and ground control. By 1990 one TDRS satellite could relay all the data in a twenty-four volume encyclopedia in five seconds. The new TDRS converts solar energy to electricity and uses antennas to transmit up to 300 million bits of information per second per radio channel. The latest versions allow communication between spacecrafts, between a shuttle and a space station, or with the Hubble Space Telescope.
There is also now a mobile telecommunications network which provides data digital links and telephone and fax communication between ships or with airplanes on international flights. Ships can also use two satellites at two different locations for navigation purposes. Laser beams, operating in the blue-green wavelength which penetrates water, have been used for communication between satellites and submarines.
In the early 2000s, developments in satellites use networks of small satellites in low earth orbit (1,200 miles or less above the earth) to provide global telephone communications. The special telephones used allow access to regular telephone networks from anywhere on the globe, creating a true "global village."
BIBLIOGRAPHY
Curtis, Anthony R. ed. Space Almanac. Houston: Gulf Publishing Co., 1992.
McGraw Hill Encyclopedia of Space. West Germany: Editions Rombaldi, 1967.
Diane NagelPalmer