The Iridium Network:

Proliferation of mobile phones is already a fact, but worldwide mobile telephone communication has become possible only with the advent of the Iridium Network. The network is a joint venture between US organizations Motorola and Lockheed Martin Corporation, and the Russian Krunichev State Research Space Centre. The first satellites were launched towards the end of last year; when fully operational, the network will embrace 66 satellites in various orbits around the earth at a height of some 780 kilometres (470 miles). This fairly low orbit is dictated by the relatively low power of mobile phones.