New Satellites for Personal Communications; April 1998; Scientific American Magazine; by Evans; 8 Page(s)

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.

Much of the voice traffic handled by satellites, however, is to countries that have no access to fiber-optic cables, which are the preferred medium for carrying telephone calls. Because large communications satellites are typically put into geosynchronous orbits, where they are roughly 36,000 kilometers (22,300 miles) above the same spot on the earth at all times, it takes a quarter of a second for signals to travel to and from the satellite, delaying the responses received during a conversation. Although not all users find this delay irritating, communications satellites are increasingly being used to carry television signals and data rather than voice traffic.