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The geo-stationary Inmarsat-satellites
Inmarsat operates four geo-stationary satellites which cover about 97% of the earth's surface. Only the polar caps cannot be reached due to the low elevation angles (<5o). The Inmarsat satellites serve mainly as voice (Inmarsat A/B/M) and data communication (Inmarsat C/D). Since 1996 newly launched satellites are equipped additionally with transponders with GPS-similar signals to increase redundancy in modern navigations systems.
In addition to commercial communication channels there are also transponders for emergency calls installed in Inmarsat satellites (Inmarsat-E). The 1,6-GHz-EPIRBs operate via these transponders. The picture below shows the satellite coverage.
Only one satellite is required for satisfactory operation and three of the four satellites can be reached from Europe at any time. This guarantees that a distress call is forwarded without delay and minimizes the probability of data loss during transmission.
Many more informations are available at the Inmarsat homepage.
The table gives an overview on satellite availability .
|Atlantic West||Atlantic East||Indian Ocean||Pacific Ocean|
54 o West
15.5 o West
64 o East
178 o East
|Redundant-Satellit in hot-standby
55 o West
17 o West
65 o East
175 o East
|The picture shows LES Goonhilly in England and was kindly provided by Chris Wortham.|