New Satellites for Personal Communications

The first telephone message was transmitted in 1876 from one room in Alexander Graham Bell's house to another. In 1965, with the launch of the first communications satellite, telephone messages could betransmitted globally from space. Multibillion-dollar  projects now underway could make it possible to reach someone from anywhere on earth using a handheld device similar to today's cellular telephone. This Scientific American article explores recent efforts to bring cellular telephony and internet access to people around the globe by developing fleets of new communications satellites.    Since the first commercial model was launched into orbit in 1965, the communications satellite has become a linchpin of global communications. From modest beginnings- that first satellite could handle only 240 voice circuits at a time- the technology has blossomed to the extent that satellites now carry about one third of the voice traffic between countries and essentially all the television signals between countries.     With their relatively number of satellites, the two-earth-orbit proposals would be the most expensive to deploy. Indeed, Teledesic probably remains the most advanced of all the systems being proposed and, with 288 satellites, is likely to prove rather costly. Teledesic intends to orbit the satellites at an altitude of 1,400 kilometers; the need for so many satellites was dictated partly by that orbit and partly to mitigate rain fading.(for  the latter, the service area of each satellites is to be limited to a fairly narrow cone.)