July 20, 2007: Last month, the United States became the first nation that had to change the orbit of one of their satellites to avoid the cloud of debris created when China tested an anti-satellite weapon earlier this year. China had launched an anti-satellite system (a KillSat, or Killer Satellite) that destroyed an old Chinese weather satellite, about 850 kilometers up on January 11th. That's at the upper range of where most reconnaissance satellites hang out. The KillSat hit the weather bird, and the result was several million fragments. Most of the pieces are tiny, but at least 817 are truly dangerous (at least four inches long, wide or in diameter). There are many such debris swarms up there, that have to be watched and avoided. But these other debris swarms are the result of accidents. For example, on February 19th, a new swarm was created because of the accidental explosion of a Russian rocket, that put over 1,100 dangerous fragments in orbit. Those two incidents increased the dangerous debris in orbit by about fifteen percent.

The U.S. Terra environmental satellite was in an orbit that indicated a seven percent chance of hitting debris from the Chinese KillSat test. So controllers adjusted Terra's orbit slightly, to reduce the risk to zero.

The IADC (Inter-Agency Space Debris Coordination Committee) is an international organization that coordinates the exchange of information, and space operations, as they relate manmade and natural debris in orbit around the earth. Every year, some of this stuff falls into the atmosphere and burns up, but there are always new accidents, or deliberate operations, that add more junk to the spaceways.