How many unused satellites are still floating above Earth?

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  vishal730
  Oct 20, 2011

  Satellites have approximate lifespan and according to the Federal Communications Commission when the end of its lifespan is near, satellites that are orbiting the earth at a height lower than 36,000 kilometers need to be programmed or navigated to a higher plane of about 300 kilometers from its original height. In addition, these satellites nearing their end of life should be deactivated by discharging its batteries or removing active gases. This is to ensure continued safety and prevent collision with other satellites. In some cases when collision and subsequent explosion actually happens, more space debris are created and these are added to the thousand of objects that space agencies monitor.

  Some lower-altitude satellites, however, are left in orbit or brought down to a lower altitude that will ensure it will come back to earth in about 25 years time. Space surveillance systems keep track of all these satellites and space debris to ensure we have sufficient warning in case any of these fall back to earth.

  According to wired magazine (http://www.wired.com/magazine/tag/space-surveillance-network/), in 2010, there are about 3,700 unused satellites that are still in space compared to only about 1,000 which are active. Add to this more than 15,000 space debris that are out there that sparks growing concerns to possible dangerous collisions.