Communications satellites (often called “comsats”) are one of the most important types of spacecraft. They allow people to communicate by telephone over vast distances and relay television and radio signals to the ground for entertainment purposes.

The possibility of using satellites in orbit to communicate messages to the ground was probably first proposed in an 1869 short story published in the Atlantic Monthly by Edward Everett Hale. The story, called “The Brick Moon,” discussed a human-occupied satellite made of bricks intended as a navigational aid. But it was accidentally launched into orbit while its builders were still aboard. They communicated with the ground by jumping up and down on the surface in sequence to symbolize Morse code to a ground observer watching them through a telescope.

The first actual communications satellite was the Moon. In the 1950s, the U.S. Navy developed a system for bouncing signals off the surface of the Moon to the continental United States from Hawaii and also from the mainland to Hawaii. This system was crude and only worked when the Moon was in the right position, but it demonstrated that objects in orbit around the Earth could aid in communicating over long distances. Later, the United States used the Moon to detect radar signals in the Soviet Union and determine their capabilities.

In 1945, a young British scientist by the name of Arthur C. Clarke proposed placing three satellites in very high geosynchronous Earth orbit (often simply called GEO). Clarke noted that three satellites spaced evenly around the globe in geosynchronous orbit could view the Earth's entire surface and therefore be able to relay communications for the entire planet. Clarke initially envisioned an inhabited space station at this altitude because only humans could replace the worn-out vacuum tubes on board the satellite. Only a few years later the development of the transistor made the idea of geosynchronous communications satellites much more practical because the transistor in place of the vacuum tube was smaller, used less power, and lasted much longer than the older technology.

In December 1958 the U.S. Air Force orbited an entire Atlas rocket equipped with a tape recorder. This spacecraft, designated SCORE (for Signal Communications Orbital Relay Experiment), was primarily a propaganda stunt. But it demonstrated that a satellite could communicate with people around the globe and not simply relay scientific data to government engineers. The first artificial satellite to relay a real-time voice message from the ground to space and then back was a mylar-covered balloon named Echo-1. AT&T scientist John Pierce had suggested using it for bouncing signals as the Navy had done with the Moon. Echo-1 was launched on August 12, 1960.

Soon after, in October 1960, the U.S. Air Force launched Courier 1B, which was a low-Earth-orbit satellite that could receive and re-transmit signals. It had solar and battery power but could only transmit a little information at a time and was therefore impractical for regular communications.

At this time, telephone conversations across the oceans were sent through huge undersea copper cables. These cables were expensive to put in place and maintain and satellites represented a potentially cheaper way to accomplish the same task. In particular, communications giant American Telephone and Telegraph (AT&T) wanted to develop them, but White House officials feared that AT&T could gain a monopoly in this new field. In 1962, after a raucous debate in Congress, President John F. Kennedy signed the Communications Satellite Act of 1962 that created the Communications Satellite Corporation (Comsat).

On July 10, 1962, the National Aeronautics and Space Administration (NASA) launched an experimental satellite built by AT&T called Telstar. The satellite had a perigee (the point in an orbit closest to the Earth) of 570 miles (917 kilometers). At such an orbit, a fleet of 12 to15 satellites would be needed for an operational system. Telstar looked like a beach ball covered with solar cells and was primarily an experimental satellite. It was used to relay television signals from France to the United States in addition to telephone transmissions. It proved that satellite communications was not only practical but also had broad commercial applications.

Once satellites began flying in 1957, many space engineers recognized that GEO, or “Clarke orbit” as it was sometimes called, was the best place to put a communications satellite. The U.S. Air Force and Army even started work on an ambitious military communications satellite called Advent, which would have operated in geosynchronous orbit. The problem was that early rockets lacked the power to put satellites into these distant orbits and bigger rockets, particularly with higher-powered upper stages, were needed to make such satellites practical.

In 1963, Hughes Aircraft, using both its own and NASA funds, developed Syncom, a communications satellite for operating in geosynchronous orbit. Syncom 1 suffered a propulsion failure and never reached proper orbit. But Syncom 2, launched in December 1963, proved that a communications satellite could operate successfully in geosynchronous orbit. Syncom 3 was even more successful, and the U.S. Department of Defense also used it for experiments. Comsat hired Hughes to build an updated version of Syncom popularly known as “Early Bird.” It weighed only 85 pounds (39 kilograms) and was launched in April 1965, becoming the first operational commercial comsat.

Over the next decade, various companies produced bigger comsats to operate in geosynchronous orbit, with Hughes dominating the field. All of these early satellites spun around a long axis (called spin stabilization) to remain stable. In 1974 Fairchild Space and Electronics Company and Ford Aerospace built ATS-6 for NASA. This was the first 3-axis stabilized geosynchronous communications satellite, meaning that it used a special system of gyroscopes to remain pointed in a specific direction (or attitude). The benefit of this design was that the satellite could carry large solar panels to provide more power. The satellite had a huge 9.14-meter parabolic antenna. Ford Aerospace eventually developed Intelsat-5, the first commercial 3-axis stabilized satellite.

When Arthur C. Clarke had proposed placing communications satellites in geosynchronous orbit, he thought that three evenly spaced satellites could cover most of the world. The reality is that GEO satellites cannot transmit well to northern regions because their signals have to go through too much atmosphere. This was particularly a problem for the Soviet Union (and Russia today) because so much of its landmass was located far north. In 1965 the Soviet Union launched its Molniya (which means “Lightning”) communications satellite into a highly elliptical orbit (HEO) that carried it high over the northern hemisphere where it appears to hang in the sky for the majority of its orbit. Russia still uses this technique as well as a system of small satellites that record transmissions at one point and relay them when they fly over the destination. France and West Germany fielded the first European communications satellite, the Symphonie 3-axis stabilized satellite in December 1974. Japan, Italy and other countries also followed, although they were slow to develop a commercial satellite manufacturing industry.

During the 1970s, Hughes, Ford, and a few other manufacturers built larger and more powerful comsats. Hughes' drum-shaped Intelsat IV series represented an important milestone because of its increased power, and served as the basis for a series of highly classified relay satellites for American KH-11 spy satellites. Starting in the early 1980s, Hughes developed a slightly bigger satellite named the HS-376, which is still built today at the rate of approximately one a year. The company also built a truly massive series of “spinners” known as the Intelsat VI. In the mid-1980s Hughes introduced its large 3-axis stabilized satellite the HS-601. By the late 1990s, it introduced the even larger HS-701. In 2000, Hughes Satellite Communications was purchased by Boeing and continues to be a major manufacturer of commercial and military communications satellites. Today Space Systems/Loral and Lockheed Martin are also major competitors in the comsat field. Although several European companies like Alcatel, Matra Marconi, and Aerospatiale build comsats, the industry is dominated by U.S. firms.

As more and more comsats began to take up positions in geosynchronous orbit, comsat designers and operators were presented with the problem of their satellite signals interfering with each other. This required careful international regulation and meant that satellites were assigned specific spots. Geosynchronous “real estate” thus became an important issue for operators and manufacturers and was one reason for the development of ever larger comsats able to pack more transmission capability into a single satellite.

Starting in the late 1980s, several companies began considering placing satellites in low Earth orbit (LEO) and using them for communicating with small, hand-held receivers. The first such system was operated by a consortium named Iridium, and went into operation in the late 1990s. Other companies such as Globalstar and Teledesic followed and this fueled a brief boom in the rocket industry. But their systems required many satellites with sophisticated equipment for relaying signals from one satellite to another and they had to compete with both cell phones and fiber optic cables. None of these companies was successful and they all went out of business; only Iridium managed to emerge successfully from bankruptcy.

--Dwayne Day

Sources and Further Reading:

Butrica, Andrew J. Beyond the Ionosphere: Fifty Years of Satellite Communication. NASA SP-4217. Washington, D.C.: National Aeronautics and Space Administration, 1997.

Hale, Edward E. “The Brick Moon,” in Logsdon, John M., et al, eds. Exploring the Unknown, Vol. I. NASA SP-4407. Washington, D.C.: National Aeronautics and Space Administration, 1996.

Martin, Donald H. Communication Satellites, Fourth Edition. El Segundo, Cal.: The Aerospace Press and the American Institute of Aeronautics and Astronautics, 2000.

Pelton, Joseph N. “The History of Satellite Communications,” in Logsdon, John M., et al, eds. Exploring the Unknown, Vol. III. NASA SP-4407. Washington, D.C.: National Aeronautics and Space Administration, 1998.

Smith, Delbert D. Communication via Satellite: A Vision in Retrospect. Boston: A.W. Sijthoff, 1976.

Whalen, David J. The Origins of Satellite Communications, 1945-1965. Washington, D.C.: Smithsonian Institution Press, 2002.

Alcatel Space: Space Solutions for Civil and Military Applications.”http://www.alcatel.com/space/

Glover, Daniel. “NASA Experimental Communications Satellites.” http://roland.lerc.nasa.gov/~dglover/sat/satcom2.html

“Iridium Satellite Solutions.” http://www.iridium.com

Lockheed Martin Corporation. http://www.lockheed-martin.com

Matra Marconi Space.http://www.ukspace.com/profiles/matmarsp.htm

“Space and Communications.” http://www.boeing.com/history/boeing/planning.html

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