Mobile satellite systems.

Satellite communication is a technique which has been used in telemedicine, often for educational purposes. Almost all of the work has concerned the use of fixed satellite terminals. Mobile satellite services (MSS) provide two-way voice and data communication from hand-held terminals, where the final link to the subscriber is by satellite. A number of new MSS systems are expected to become operational by 2001, providing either regional or global coverage. The most well developed proposals are Globalstar, ICO, Iridium and Odyssey. All the proposed systems use non-geostationary satellites. The MSS systems will allow international travellers to make and receive calls using a unique telephone number for their handset anywhere in the world where the service has been authorized by the local regulatory authorities. Data and fax services will also be available. By 2002 the proposed MSS systems might serve a million subscribers in Western Europe, although this is less than 1% of the expected number of mobile phone users. To recoup the development costs, the price of MSS airtime is expected to be high compared with existing mobile phones.