 From the beginning of the Space Age, Earth’s periphery has been increasingly encumbered by all kinds of debris, primarily concentrated in Low Earth Orbit (less than 2000 km in altitude, where the International Space Station is orbiting) or Geostationary Orbit (35,786 km in altitude). Many of these objects are spent rocket stages or satellites that have broken up in orbit. If they collide with another orbiting object, say a functioning satellite, they can cause massive damage, or even destroy it. This is what happened on February 10, 2009, when the U.S. satellite Iridium-33 exploded upon impact with the abandoned Russian satellite Cosmos-2251. The financial consequences of these collisions are enormous, particularly for insurance companies involved in the space sector; a sum currently estimated at $20 billion to insure existing satellites.
Cases such as this one are bound to increase in number. Even in the immensity of outer space, the increasing density of human-generated waste is becoming a problem. It’s expanding exponentially, because each collision generates in turn several thousand more fragments, which, although smaller, are no less dangerous than a large, abandoned satellite. NASA, which tracks 16,000 of these objects, can only monitor the largest ones (greater than 10 cm in diameter) – but at these incredible speeds even a simple paint chip can seriously damage a solar panel or the window on a shuttle. To avoid the largest objects before they get critically close, the International Space Station must constantly alter its orbit. It managed to do this again just recently, on January 29, 2012.
Last year the Swiss Re insurance company published a study showing that every year, there is a nearly one in 10,000 chance that a 10 m2 satellite traveling in a sun-synchronous (600-1,000 km) orbit will collide with a piece of space debris larger than 1 cm.