Communications satellites, or comsats, are artificial devices used for communication links. They provide a variety of communication needs, including television broadcasting and communication with ships and aircraft. Comsats operate in different orbital patterns, with geostationary satellites being widely used for television broadcasting. They have become popular for broadband transmissions and are used in military communications. Comsats are considered one of the most influential technologies of the 20th century.
A communications satellite, or comsat, is an artificial space-orbiting device used to create communication links. Using advanced radio transmission technology and different orbital patterns, comsats provide a variety of communication needs, including television broadcasting and communication with ships and aircraft. A communications satellite is especially useful where terrestrial cables are inconvenient or impossible to use.
The first communications satellite, Sputnik 1, was launched in 1957 by the Soviet Union. Not to be outdone in the space race, the United States responded in 1958 with the launch of Project SCORE which was used to broadcast a recorded Christmas greeting around the world from President Eisenhower. The first privately sponsored communications satellite, Telstar, was launched in 1962 as a joint project between AT&T, Bell Telephone, NASA, the British General Post Office and the French National Post Office. Telstar was placed in an elliptical orbit and was the first direct relay communications satellite.
Comsats operate in a variety of orbital patterns, each with different advantages. Geostationary satellites orbit the planet once a day, centered on the Earth’s equator. The launch of Satcom 1 in 1975 led to the widespread use of geostationary comsats for television broadcasting. Low-Earth-orbit satellites, mostly used for satellite phones in remote regions, operate from about 248km above the earth and circle the globe once every 400 minutes. The Molinya orbiting comsats are a Soviet modification of the geostationary system and are used in television broadcasting and radio communications, particularly in high-latitude areas.
Recently, communication satellites have become popular in the use of broadband transmissions. In 2004, XM and Sirius satellite radio stations were introduced to the public. Beginning in the late 20th century, broadband internet was transmitted using a comsat network. This technology is especially useful in remote or hard-to-access regions where it is sometimes impossible to get dial-up connections.
Two types of communications satellite are often used in television broadcasting. Direct Broadcast Satellites (DBS) are used to transmit TV to home satellite dishes, as seen with North American companies DirecTV and Dish Network and United Kingdom (UK) company BSkyB. In the 21st century, India, Germany and the UK have started work on free TV stations using DBS technology.
Fixed Service Satellites (FSS) are also used for TV broadcasting, but more frequently to send information from a parent organization to local network affiliates or to show live events. FSS comsats are also used to broadcast lessons between schools and universities, called “distance learning. This type of communications satellite requires a much larger antenna to perform well and has largely been overtaken by the popularity of DBS systems.
Comsats have become an important element of military communications around the world. The US military is now heavily reliant on the Global Command and Control System (GCCS). This comsat system is highly secure and used as a method of communication between US bases, theaters of action and headquarters of military branches. The GCCS is also believed to be vital in US intelligence gathering.
After computers, communications satellites are considered by many to be the most influential technology of the 20th century. With ever-expanding applications of satellite capabilities, the sky is now littered with hundreds of comsats, often visible in the night sky. Most experts agree that it is no exaggeration to say that most communications in the 20th century are conducted over satellite communications networks.
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