If Iridium works as planned, clients will be able to make voice, data, fax, and pager transmissions from anywhere, to anywhere - a European hotel, the summit of Mount Everest, or aboard a ship in the middle of the Black Sea. The service targets business travelers, mobile workers, and those who reside in areas not served by land-based networks. Getting to the brink of launching this type of service is no small feat for any project. Odyssey aimed to deploy a constellation of satellites 5,580 miles above Earth to deliver fixed and mobile voice and data at a cost to the consumer of roughly 65 to 95 cents per minute. The system was intended to augment earthbound communications networks by connecting to various local loops as well as far-reaching territories.
Iridium is a more complex and ambitious project.
It will use both the terrestrial communications network through gateways it has constructed in 11 countries as well as intersatellite connections to send calls through the stratosphere. This latter task is a complex relay in which one satellite hands off its load to another when the first satellite approaches the horizon for a given coverage area. It's a feat never before attempted, let alone accomplished. The transfer requires a piece of the radio spectrum beyond what all satellite systems use. All satellite communications systems require two distinct avenues for transmissions between the heavens and Earth, and these are commonly called uplink and downlink frequencies.