Over C by Satellite
Four satellites 22,500 miles above the equator enable the BT Global Challenge Race HQ in Southampton, UK to monitor the fleet 24 hours a day using a state-of-the-art C-Sat communications system that allows the plotting each yacht's progress on computer.  The satellites are positioned over the equator above the East and West Atlantic, Indian and Pacific oceans, with overlapping coverage that ensures communications to and from mobile terminals worldwide. They are provided and maintained by the international Inmarsat organisation, of which BT is a founder member and the UK signatory. The satellites mean that mobile communications equipment known as mobile earth stations can be used at land or sea around the globe. Small vessels such as the BT Global Challenge yachts generally use C-Sat, a store-and-forward messaging and data transfer service using lightweight equipment. The link between the satellites and Race HQ is via BT's earth station in Goonhilly, Cornwall, as well as partner stations at Eik in Norway and Sentosa in Singapore.  The position of each of the yachts is relayed via satellite every six hours in a single text message to Race HQ. The race officers can check positions at any other time by sending a message to trigger a yacht's C-Sat transceiver to give a location accurate to within a few metres, within minutes, or even seconds. Each yacht carries an identical lightweight transceiver and a conical antenna about the size of a vacuum flask. An integral part of C-Sat is the Global Positioning System (GPS) receiver which calculates the yacht's position and feeds it into the transceiver.
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