earth station


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earth station

[′ərth ‚stā·shən]
(communications)
A facility with a land-based antenna used to transmit and receive information to and from a communications satellite.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

earth station

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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References in periodicals archive ?
The cost of a micro earth station communication network is closely related to the characteristics and quantity of data to be transferred.
The 18 streams are processed for transmission to an earth station. Data streams with rates higher than 200 Mbit/s must be separated into two or more streams for transmission to the Earth, while channels with lower data rates may be combined with other streams.
In other words, where a transmitting earth station is placed could cause interference with already in-place terrestrial microwave systems.
The ability to set up short-term, transmitting earth stations even in crowded microwave environments has created a significant industry in temporary satellite uplinks.
A hotel can buy its earth station outright or lease it as part of a total communications service that includes in-room entertainment programming and videoconferencing services.
In addition, Comsat says it's planning to build an earth station at the facility, for operation next year, following FCC approval.
The commission tentatively concluded that individual ownership and operation of earth station operating with the Intelsat system would permit barriers to build their own stations as marketplace forces dictate, providing users with additional choices, while reducing earth station rates.
The basic transmit/receive earth station consists of the following subsystems: antenna subsystem; low-noise amplifier subsystem; downlink subsystem; uplink subsystem; and earth station controller (optional).
Globalstar Canada is a partnership between Canadian Satellite Communications, Loral Space & Communications and Vodafone Airtouch Plc for the provision of Globalstar's satellite services to subscribers through earth station gateways in Ontario and Alberta.
New and simpler earth station designs, based on offset feed and phased array devices, as well as improved manufacturing techniques, new materials and continued breakthroughs in solid-state electronics have made lower costs possible.