Earth station

From Wikipedia, the free encyclopedia

An earth station or ground station is the surface-based (terrestrial) end of a communications link to an object in outer space. The space end of the link is occasionally referred to as a space station (though that term often implies a human-inhabited complex).

An Earth Station with several antennas

The majority of earth stations are used to communicate with communications satellites, and are called satellite earth stations or teleports, but others are used to communicate with space probes, and manned spacecraft. Where the communications link is used mainly to carry telemetry or must follow a satellite not in geostationary orbit, the earth station is often referred to as a tracking station.

Examples of earth stations include:

1 Communications
2 Teleports
3 Cultural References
4 References
5 External links

[edit] Communications

A satellite earth station is a communications facility with a microwave radio transmitting and receiving antenna and required receiving and transmitting equipment for communicating with satellites (also known as space stations).

In the satellite communications industry there are international standards agreed through the International Telecommunications Union (ITU) Radiocommunication Sector (ITU-R, formerly the CCIR) and de facto standards set by Intelsat for satellite earth stations of differing capabilities. They are known as 'Intelsat Earth Station Standards' or 'IESS'. A major defining property is not the size of the 'dish', but the overall antenna gain achieved by the system and the geometry of its sidelobes. In general, however, larger dishes give higher gains. The different types of Intelsat satellite earth station are designated by the word 'Standard' followed by a letter:

Standard A - nominal G/T: 35.0 dB/K, 4 & 6 GHz bands C band

Dish diameter usually >26 metres (older), approx 15 metres (newer)

Standard B - nominal G/T: 31.7 dB/K, 4 & 6 GHz bands C band

Dish diameter typically 11-13 metres

Standard C - nominal G/T: 37.0 dB/K, 11 & 14 and/or 12 & 14 GHz bands K_u band
Standard E-1 - nominal G/T: 25.0 dB/K, 11 & 14 and/or 12 & 14 GHz bands K_u band

Dish diameter 3.05±0.65 metres (K_u-band)

Standard E-2 - nominal G/T: 29.0 dB/K, 11 & 14 and/or 12 & 14 GHz bands K_u band

Dish diameter 5.0±1.3 metres (K_u-band)

Standard E-3 - nominal G/T: 34.0 dB/K, 11 & 14 and/or 12 & 14 GHz bands K_u band
Standard F-1 - nominal G/T: 22.7 dB/K, 4 & 6 GHz bands C band

Dish diameter 4.3±0.6 metres (C-band)

Standard F-2 - nominal G/T: 27.0 dB/K, 4 & 6 GHz bands C band

Dish diameter 6.3 metres (C-band)

Standard F-3 - nominal G/T: 29.0 dB/K, 4 & 6 GHz bands C band

Dish diameter 7.3 metres (C-band)

Standard G - no defined G/T

Dish diameter 4.1±3.2 metres (C-band), 3.6±2.7 metres (K_u-band)

Standard H-2 - nominal G/T: 15.1 dB/K, 4 & 6 GHz bands C band

Dish diameter 2.12±0.32 metres (C-band)

Standard H-3 - nominal G/T: 18.3 dB/K, 4 & 6 GHz bands C band

Dish diameter 2.42±0.02 metres (C-band)

Standard H-4 - nominal G/T: 22.1 dB/K, 4 & 6 GHz bands C band
Standard K-2 - nominal G/T: 19.8 dB/K, 11 & 14 and/or 12 & 14 GHz bands K_u band

Dish diameter 1.5±0.3 metres (K_u-band)

Standard K-3 - nominal G/T: 23.3 dB/K, 11 & 14 and/or 12 & 14 GHz bands K_u band

Dish diameter 2.1±0.3 metres (K_u-band)

Standard M

Note that satellite earth stations need not be fixed in position. Some terminals may be ship-borne, or vehicle-borne, and others are man-portable, although used only when stationary. These may better be formally termed Mobile Earth Stations, Aircraft Earth Stations or Ship Earth Stations according to Article 1 of the Radio Regulations.

Note also that the uplink (earth station to satellite) frequency is usually the higher frequency listed. See Ku- and C BAND SATELLITES UPLINK, DOWNLINK and TRANSLATION FREQUENCIES. Miteq, New York. Retrieved on 2006-09-11..

Other large industry organisations include INMARSAT and EUTELSAT, each with its own preferred antenna designs.

[edit] Teleports

A teleport is a communication facility designed to communicate with commercial satellites in orbit around the earth. In addition, a teleport facility provides satellite transmission and reception services to multiple satellites or clients, or both.

Teleports were originally constructed during the middle to latter part the decade that began in 1960 by the companies that constructed, launched and operated commercial and government communication satellites.

The main tasks of the teleport are:

Raising programs to the satellite.
Reception of signals from the satellite for control of signal presence at the satellite and its quality.
Providing permanent capacity for work of the satellite channel.

Some teleport facilities offer global coverage through the Intelsat, Eutelsat, Arabsat, Nilesat, Thaicom, Telstarand Amos satellites. C, Ku and Ka band teleport services are often provided.

A teleport can uplink taped programs like video press releases, or live teleconferences. Studios and teleproduction facilities are connected directly to the uplink via microwave or optical fiber. A signal contribution through a satellite is also possible. In this case the teleport provides "turnaround" service, which means that the channel is received from one satellite and re-transmitted on another satellite.

[edit] Cultural References

In the finale of Jeff Wayne's Musical Version of The War of the Worlds the anonymous NASA technician from Pasadena refers to a number of tracking stations in an effort to make contact with the rest of the Earth, supposedly invaded by the second wave of Martian attack. The stations referred to are Bermuda, Houston, DSS-43 Canberra and DSS-63 Madrid.