Communications Satellite Technology

Summary

Communications satellite technology has evolved from its first applications in the 1950s to become a part of most people's daily lives and thereby producing billions of dollars in yearly sales. Communications satellites were initially used to help relay television and radio signals to remote areas of the world and to aid navigation. Weather forecasts routinely make use of images transmitted from communications satellites. Telephone transmissions over long distances, including fax, cellular phones, pagers, and wireless technology, are all examples of the increasingly large impact that communications satellite technology continues to have on daily, routine communications.

Definition and Basic Principles

Sputnik 1, launched on October 4, 1957, by the Soviet Union, was the first artificial satellite. It used radio transmission to collect data regarding the distribution of radio signals within the ionosphere in order to measure density in the atmosphere. In addition to space satellites, the most common artificial satellites are the satellites used for communication, weather, navigation, and research. These artificial satellites travel around the Earth because of human action, and they depend on computer systems to function. A rocket is used to launch these artificial satellites so that they will have enough speed to be accelerated into the most common types of circular orbits, which require speeds of about 27,000 kilometers per hour. Some satellites, especially those that are to be used at locations far removed from the Earth's equator, require elliptical-shaped orbits instead, and their acceleration speeds are 30,000 kilometers per hour. If a launching rocket applies too much energy to an artificial satellite, the satellite may acquire enough energy to reach its escape velocity of 40,000 kilometers per hour and break free from the Earth's gravity. It is important that the satellite be able to maintain a constant high speed. If the speed is too low, gravity may cause the satellite to fall back down to the Earth's surface. There are also natural satellites that travel without human intervention, such as the Moon.

Background and History

In 1945, science fiction writer Arthur C. Clarke first described the concept of satellites being used for the mass distribution of television programs in his article “Extra-Terrestrial Relays,” published in Wireless World. John Pierce, who worked at Bell Telephone Laboratories, further expanded on the idea of using satellites to repeat and relay television channels, radio signals, and telephone calls in his article “Orbital Radio Relays,” published in the April 1955, issue of Jet Propulsion. The first transatlantic telephone cable was opened by AT&T in 1956. The first transatlantic call was made in 1927, but it traveled via radio waves. The cable vastly improved the signal quality. The Soviet Union launched Sputnik 1, the first satellite, in 1957, which began the Space Race between the Soviet Union and the United States. The Communications Satellite Act of 1962 was passed by the United States Congress to regulate and assist the developing communications satellite industry. The first American television satellite transmission was made on July 10, 1962, five years into the Space Race, with the National Space and Aeronautics Administration's (NASA) launch of the world's first communications satellite, AT&T's Telstar.

The many new communications satellites followed, with names such as Relay, Syncom, Early Bird, Anik, Westar, Satcom, and Marisat. Since the 1970s, communications satellites have allowed remote parts of the world to receive television and radio, primarily for entertainment purposes. Technology advances have continued to evolve and now use these satellites to facilitate mobile phone communication and high-speed Internet applications.

How It Works

Communications satellites orbit the Earth and use microwave radio relay technology to facilitate communication for television, radio, mobile phones, weather forecasting, and navigation applications by receiving signals within the six-gigahertz (GHz) frequency range and then relaying these signals at frequencies within the four-GHz range. Generally there are two components required for a communications satellite. One is the satellite itself, sometimes called the space segment, which consists of the satellite and its telemetry controls, the fuel system, and the transponder. The other key component is the ground station, which transmits baseband signals to the satellite via uplinking and receives signals from the satellite via downlinking.

These communications satellites are suspended around the Earth in different types of orbits, depending on the communication requirements.

Geostationary Orbits.Geostationary orbits are most often used for communications and weather satellites because this type of orbit has permanent latitude at zero degrees, which is above the Earth's equator, and only longitudinal values vary. The result is that satellites within this type of orbital can use a fixed antenna that is pointed toward one location in the sky. Observers on the ground view these types of satellites as motionless because their orbit exactly matches the Earth's rotational period. Numerically, this movement equates to an orbital velocity of 1.91 miles per second, or a period of 23.9 hours. Because this type of orbit was first publicized by the science fiction writer Arthur C. Clarke in the 1940s, it is sometimes called a Clarke orbit. Systems that use geostationary satellites to provide images for meteorological applications include the Indian National Satellite System (INSAT), the European Organisation for the Exploitation of Meteorological Satellites' (EUMETSAT) Meteosat, and the United States' Geostationary Operational Environmental Satellites (GOES). These geostationary meteorological satellites provide the images for daily weather forecasts.

Molniya Orbits. Molniya orbits have been important primarily in the Soviet Union because they require less energy to maintain in the area's high latitudes. These high latitudes cause low grazing angles, which indicate angles of incidence for a beam of electromagnetic energy as it approaches the surface of the Earth. The angle of incidence specifically measures the deviation of this approach of energy from a straight line. As a result, geostationary satellites would orbit too low to the Earth's surface and their signals would have significant interference. Because of Russia's high latitudes, Molniya orbits are more energy efficient than geostationary orbits. The word Molniya comes from the Russian word for “lightning,” and these orbits have a period of twelve hours, instead of the twenty-four hours characteristic of geostationary orbits. Molniya orbits have a large amount of incline, with an angle of incidence of about 63 degrees.

Low Earth Orbits. Low earth orbit (LEO) refers to a satellite orbiting between 140 and 970 kilometers above the Earth's surface. The periods are short, only about ninety minutes, which means that several of them are necessary to provide the type of uninterrupted communication characteristic of geostationary orbits, which have twenty-four-hour periods. Although a larger number of LEOs are needed, they have lower launching costs and require less energy for signal transmission because of how close to the Earth they orbit.

Applications and Products

DISH Network and Direct Broadcast Satellites. DISH Network is a type of direct broadcast satellite (DBS) network that communicates using small dishes that have a diameter of only 18 to 24 inches to provide access to television channels. This DBS service is available in several countries through many commercial direct-to-home providers, including DIRECTV in the United States, Freesat and Sky in the United Kingdom, and Bell TV in Canada. These satellites transmit using the upper portion of the microwave Kμ band, which has a range of between 10.95 and 14.5 GHz. This range is divided based on the geographic regions requiring transmissions. Law enforcement also uses the frequencies of the electromagnetic spectrum to detect traffic-speed violators.

Fixed Service Satellites. Besides the DBS services, the other type of communication satellite is called a fixed service satellite (FSS), which is useful for cable television channel reception, distance learning applications for universities, videoconferencing applications for businesses, and local television stations for live shots during the news broadcasts. Fixed service satellites use the lower frequencies of the Kμ bands and the C band for transmission. All of these frequencies are within the microwave region of the electromagnetic spectrum. The frequency range for the C band is about 4 to 8 GHz, and generally the C band functions better when moisture is present, making it especially useful for weather communication.

Intercontinental Telephone Service. Traditional landline telephone calls are relayed to an Earth station via the public switched telephone network (PSTN). Calls are then forwarded to a geostationary satellite to allow intercontinental phone communication. Fiber-optic technology is decreasing the dependence on satellites for this type of communication.

Iridium Satellite Phones. Iridium Communications is one of the world's largest mobile satellite communications companies. Satellites are useful for mobile phones when regular mobile phones have poor reception. These phones depend only on open sky for access to an orbiting satellite, making them very useful for ships on the open ocean for navigational purposes. Iridium manufactures several types of satellite phones, including the Iridium Extreme and Iridium 9555, and models that have water resistance, e-mail, and USB data ports. Iridium faces competition from two other satellite phone companies: Immarsat and Globalstar.

Satellite Trucks and Portable Satellites. Trucks equipped with electrical generators to provide the power for an attached satellite have found applications for mobile transmission of news, especially after natural disasters. Some of these portable satellites use the C-band frequency for the transmission of information via the uplink process, which requires rather large antennas, whereas other portable satellites were developed in the 1980s to use the Ku band for transmission of information.

Global Positioning System (GPS).GPS makes use of communications satellite technology for navigational purposes. The GPS was first developed by the government for military applications but has become widely used in civilian applications in products such as cars and mobile phones.

Careers and Course Work

Careers working with communications satellite technology can be found primarily in the radio, television, and mobile phone industries. Specifically, these careers involve working with the wired telecommunications services that often include direct-to-home satellite television distributors as well as the newer wireless telecommunications carriers that provide mobile telephone, Internet, satellite radio, and navigational services. Universities such as Ohio University and the University of Louisiana offer degree courses in satellite communications. Government organizations also need employees who are trained in working with communications satellite technology for weather forecasting and other environmental applications as well as communication of data between public-safety officials.

The highest salaries are earned by those with a bachelor's degree in avionics technology, computer engineering, computer science, computer information systems, electrical engineering, electronics engineering, physics, or telecommunications technology, although a degree in television broadcast technology can also lead to lucrative career after obtaining several years of on-the-job-training. The work environments for those with these types of degrees are primarily office and technology, with more than 14 percent of the workers working more than 40 hours per week. Although the telecommunications and communications technology industries are expected to continue to grow faster than many other industries, the actual job growth is expected to be less than other high-growth industries because of computer optimization. Those without a bachelor's degree are the most at-risk, as their jobs also can involve lifting and climbing around electrical wires outdoors in a variety of weather and locations. The National Coalition for Telecommunications Education and Learning (NACTEL), the Communications Workers of America (CWA), and the Society of Cable Telecommunications Engineers (SCTE) are sources of detailed career information for anyone interested in communications satellite technology.

Social Context and Future Prospects

Advances in satellite technology have accompanied the rapid evolution of computer technology to such an extent that some experts describe this media revolution as an actual convergence of all media (television, motion pictures, printed news, Internet, and mobile phone communications). In 1979, Nicholas Negroponte of the Massachusetts Institute of Technology began giving lectures describing this future convergence of all forms of media. As of the twenty-first century, this convergence seems to be nearly complete. Television shows can be viewed on the Internet, as can news from cable television news stations such as CNN, Fox, and MSNBC. Hyperlinks provide digital connections between information that can be accessed from almost anywhere in the world instantly because of communication satellite technology. The result is that there is a twenty-four-hour news cycle, and the effects are sometimes positive but can also be negative if the wrong information is broadcast. The instantaneous transmission of political and social unrest by communications satellite technology can lead to further actions, as shown by the 2011 Arab Spring protests in Egypt, Iran, Yemen, Libya, and Bahrain.

Advancements in technologies such as cloud computing, 5G (fifth generation of cellular networks), and artificial intelligence (AI) have significantly improved efficiency and competence. Measures are also being taken to provide wide-ranging and expandable 5G wireless broadband in the US countryside for better connectivity. The 5G Internet of things (IoT) market size was around US$2.6 billion in 2021 and was expected to increase in the future.

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