Satellite phone
From Wikipedia, the free encyclopedia
A satellite telephone, satellite phone, or satphone is a mobile phone that communicates directly with orbiting communications satellites. Depending on the architecture of a particular system, coverage may include the entire Earth, or only specific regions.
The mobile equipment, also known as a terminal or earth station, varies widely. A satellite phone handset has a size and weight comparable to that of a late 1980s or early 1990s mobile phone, but with a large retractable antenna. These are popular on expeditions into remote areas where terrestrial cellular service is unavailable.
A fixed installation, such as used shipboard, may include large, rugged, rack-mounted electronics, and a steerable microwave antenna on the mast that automatically tracks the overhead satellites.
Satellite phones are usually issued with numbers in a special country calling code. For example, Inmarsat satellite phones are issued with codes +870 through +874, while Iridium satellite phones are issued with codes +881 6 and +881 7. Some satellite phones are issued with ordinary phone numbers, such as Globalstar satellite phones issued with U.S. telephone numbers.
[edit] Geostationary services
Some satellite phones use satellites in geostationary orbit. These systems can maintain near-continuous global coverage with only three or four satellites, reducing the launch costs. The major satellite system in civilian use is Inmarsat.
The disadvantage of geostationary satellite systems is that because the satellite is so far away (approx. 22,000 miles), a comparatively large antenna system is required for signal transmission and reception. The physical phone system must therefore be quite large compared to current terretrial mobile phones. They are similar in size to terrestrial mobile phones of the past.
One serious disadvantage of satellite phones is that the handheld units need a clear view of the sky. Thus they will not work inside buildings, cars or boats, regardless of where they are made out to work in tv-shows and movies. External antennas are required for these uses.
[edit] Low Earth orbit
LEO telephones utilizes LEO (low Earth orbit) satellite technology. The advantages include providing worldwide wireless coverage with no gaps. Newer satellite phones tend to be LEOs. LEO satellites orbit the earth at high speed, low altitude orbits with an orbital time of 70–90 minutes, an altitude of 640 to 1120 kilometres (400 to 700 miles), and provide coverage cells. Since the satellites are not geosynchronous, they must fly complete orbits and thus further guarantee complete coverage over every area by at least one satellite at all times. Blimps are being considered as an alternative to satellites.
The two deployed LEO satellite systems are Iridium and Globalstar. Customer numbers for both systems never matched the levels required to fund the large number of satellite launch costs, and both went into bankruptcy. They are now operated by new owners who bought the assets for a fraction of their original cost.
There are several models of satellite phones available.
[edit] Satellite phones in popular culture
In the movie Jurassic Park III, Paul Kirby lends his satellite phone (Globalstar handset) to mercenary M.B. Nash during after a plane crash on Isla Sorna. A Spinosaurus eats Nash and the phone is later found in its feces. The satellite phone was also used many times on the show Relic Hunter. The main character, Sydney Fox, would use it to communicate back home when she found interesting relics. Also such phones are said to be difficult to trace which makes them a popular favorite for criminals.
Phones both identified as Satellite Phones and those that appear to be Satellite Phones are often used on the television drama 24. Similar phones appear in the action film Miami Vice. The Satellite Phone is also used in the film-based video game Scarface: The World is Yours.de:Satellitentelefon et:Satellittelefon ja:衛星電話 fi:Satelliittipuhelin sv:Satellittelefon
