y about making sure their satellites work but that flying garbage doesn't knock them out of commission. Studies conducted by the National Aeronautics and Space Administration show that a collision with a fragment the size of a marble would do serious damage to a satellite. A 10-centimeter piece would be enough to permanently put the satellite out of order . (5)Collisions with such debris are not rare events ; space shuttles, for example, regularly return to earth with cracked windows and pockmarks presumed to have been caused by encounters with space junk. In July 1996, a French military satellite was destroyed by a fragment from the Pegasus rocket that had carried it into space (4) . The problem is particularly acute for LEO satellites . Lower orbits must pass through the debris from the rockets that carry higher-orbiting satellites farther into space. The lower altitudes are also strewn with pieces of other satellites 130 of which have broken up in space. To make matters worse, as the numbers of satellites taken to the skies increases , the probability of collisions increases, which in turn creates more junk to threaten increasingly crowded orbit paths. Already high insurance premiums for these enterprises will get worse. Figuring out ways to protect satellites and space vehicles from space junk is not an easy task . Shields and insulation material are standard parts of satellites in low earth orbit . Furthermore companies such as Iridium and Globalstar have factored in the risk of space junk by launching extra satellites that can replace disabled ones. This raises the multibillion-dollar price tag of network deployment, but it also protects against downtime, and thus lost revenue. ( 5 )Fig 3 : A prototype of a mobile phone that will be used for communicating through LEOS . ( 5) The Major VendorsLEO proposals have so far been put forward by six different companies ( two of which are discussed in detail ) Iridium , Globastar Od...
