Satellites Again

The total number of satellites ever launched is about 2000. The operation of satellite networks, Iridium in particular, is described. Iridium has 66 satellites in orbit, enabling it to send messages from any point on Earth to any other point. Satellites past their useful life are disposed of in graveyard orbits. Geostationary satellites do not move relative to the Earth but being far away have the disadvantage of delaying the signal they process. Low Earth orbits have no noticeable delay but each one is available for relaying information for no more than 15 minutes. There was a disaster when launching one of the satellites when all three astronauts died instantly. Another notable accident was a collision between two satellites. No human life was lost but it resulted in debris that has since posed further threats to orbiting satellites.