lls to satellites .This makes phone calls in remote areas, were there is no network terrestrial coverage impossible . Although GEOS still transmit significant amounts of international telephone traffic, extensions of terrestrial telephone networks have the big market share. Nearly 60% of GEOS capacity is now used for television and video services . ( 2 p 56-57 )The solution : bring the satellites closer to earth. New companies are spending billions of dollars to launch constellations of low earth-orbiting satellites (LEOS) that will offer digital voice and data services on a global basis. There are currently six proposed LEO systems, two of which are scheduled to start commercial operations by late next year. Fig 1 : A LEO in comparison to a GEO LEOS and their advantagesLEO satellites are small communications transceivers , much smaller and lighter than GEOS .They are put in continuous motion at heights of 500-1200 miles above the earth .(Check Fig 1 ) LEOS can provide 100 percent geographic coverage, but unlike GEOS , LEO systems require less power for messages to reach their orbiting satellites , making it possible for specialised portable phones to transmit signals directly to the satellites . This makes phone calls independent of land based servers ; allowing people to be reached anywhere in the world .( Fig 2 ) Furthermore , less power requirements translate into lower service and equipment costs for users. ( 3 p. 27 ) Fig 2 : Satellites in low orbit transmitting signals to potential receivers ( 5) A major problem facing LEOS On the other hand LEO systems face a serious problem . Over 35 million bits of debris primarily pieces of old satellites, launch vehicles and solid rocket fuel currently orbit the earth, at speeds of up to seven kilometers per second. In comparison, a bullet fired from a high-speed rifle travels at only 0.8 kilometers per second. This forces LEO companies such as Iridium and Globalstar to worry not onl...
