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earth station

 
Dictionary: earth station

n.
An on-ground terminal linked to a spacecraft or satellite by an antenna and associated electronic equipment for the purpose of transmitting or receiving messages, tracking, or control.


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Computer Desktop Encyclopedia: earth station
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A ground-based receiving or transmitting/receiving station in a satellite communications system. The counterpart to the earth station is the satellite in orbit, which is the "space station." Earth stations use dish-shaped antennas, the diameters of which can be under two feet for satellite TV to as large as fifty feet for satellite operators. Antennas for space exploration have diameters reaching a hundred feet.

Multiplex, Modulate and Upconvert

An earth station is generally made up of a multiplexor, a modem, up and downconverters, a high power amplifier (HPA) and a low noise amplifier (LNA). Almost all transmission to satellites is digital, and the digital data streams are combined in a multiplexor and fed to a modem that modulates a carrier frequency in the 50 to 180 MHz range. An upconverter bumps the carrier into the gigahertz range, which goes to the HPA and dish.

Downconvert, Demodulate and Demultiplex

For receiving, the LNA boosts the signals to the downconverter, which lowers the frequency and sends it to the modem. The modem demodulates the carrier, and the digital output goes to the demultiplexing device and then to its destinations. See earth station on board vessel and base station.

Earth Station
Earth stations use dish-shaped antennas to transmit and receive microwave signals to and from satellites.

On Board a Ship
Earth stations on board vessels (ESVs) are used to receive TV, make phone calls and access the Internet while traveling near the coast or on the high seas. Encased in a waterproof container, the ESV must be able to track the satellite with great precision. If the ESV deviates by a half a degree, it must shut down transmission immediately in order to not interfere with other satellites. (Image courtesy of Sea Tel Inc., www.seatel.com)

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Wikipedia: Andover Earth Station
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The immense horn antenna within the radome at Andover Earth Station

Andover Earth Station is a satellite earth station located at Andover (44°37′58.0″N 70°41′57.0″W / 44.63278°N 70.69917°W / 44.63278; -70.69917Coordinates: 44°37′58.0″N 70°41′57.0″W / 44.63278°N 70.69917°W / 44.63278; -70.69917) in the US state of Maine. The location was selected by AT&T in December 1960. The main factors were the topography (set in the Western Maine Mountains), and the radio interference signal level. Other factors included a location in the Northeastern United States to give a short great circle path to Western Europe, it was located close enough to existing transcontinental radio relay television and telephone routes to facilitate interconnection. In addition, the site had to be large enough to accommodate an antenna structure and control building, and if necessary, provide room for expansion.

Land was purchased in January 1961, and construction of the complex began on May 1. Building construction was completed and the equipment was installed in February 1962. The Ground Station was operational in the Spring of 1962. AT&T and Bell Labs initiated, funded, constructed and took the leadership to make this project possible.

The Andover Earth Station was equipped with a giant horn antenna, 7 stories high and weighed 340 tons. To protect it from bad weather, a radome made of Dacron covered the antenna. It was 160 feet (49 m) high, 210 feet (64 m) wide and weighed 30 tons.

Telstar was launched on July 10, 1962 from the Cape Canaveral Air Force Station and went into orbit at 4:46 a.m. The engineers at the Andover Earth Station would have to wait 15 hours for the satellite, travelling at a rate of 5 miles per second (8 km/s), 3,000 miles (4,800 km) above the earth to reach within their "view". The engineers successfully sent a signal to Telstar, which amplified it 10 billion times and relayed it back to Andover.

Eugene F. O'Neill, Telstar Project Director and IEEE Fellow, oversaw the success of this project at Andover. He noted that one of the challenges was pointing an extremely sharp beam very accurately at the satellite. At 7:17 p.m. he announced "We've acquired Telstar!" At 7:31 p.m. an American flag at Andover appeared on the television screen. Then at 7:47 p.m. engineers at Andover received word that the French site, Pleumeur-Bodou, had received the television picture.

External links

The Large radome was torn down and land returned to nature in the mid 1990's

References

  • AIEE Conference Paper, "Engineering considerations in the Selection of Andover, Maine as the Location for the Bell Systems Satellite Ground Station", February 1962.

 
 

 

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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
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Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Andover Earth Station" Read more