On January 11, 2007, the People's Republic of China tested an anti-satellite (ASAT) weapon and destroyed its own Fengyun-1C meteorological satellite [5].
The incident was the largest fragmentation event in the history of manned space operations and the debris from it accounts for more than 25% of all cataloged objects in Low Earth Orbit (LEO) [6]. Large fragmentation events have a significant impact on the total number of orbiting debris and have been on the rise for the last 50 years [7]. The Fengyun-1C fragmentation event created a dramatic increase in total orbital objects during 2007, and as of January 2009, there were 2,378 Fengyun-1C fragments larger than 5 cm being tracked by the U.S. Space Surveillance Network. The total number of fragments larger than 1 cm created by the ASAT test was estimated to be greater than 150,000 [8].
If there is greater than a 1 in 10,000 chance of collision, the shuttle will maneuver away from the incoming object [9]. Similarly to NASA, mission planners for the International Space Station (ISS) rely heavily on the Space Surveillance Network to continually monitor orbital debris and determine if there is a threat to the human inhabitants on board. Like the Shuttle, the ISS can maneuver away from objects larger than 10 cm. To protect the astronauts from smaller debris, the station is the heaviest shielded vehicle ever launched into orbit and can withstand particle impacts of up to 1 cm in diameter [11]. However, the gap between survivable 1 cm objects and tracked 10 cm objects is of big concern to manned missions. With an average relative velocity of 10 km/s between two objects in LEO, an impact with anything larger than 1 cm would be catastrophic to a manned space mission [9]. With no way to avoid these intermediate-sized objects, an international focus on debris mitigation is vital to keeping space safe for future manned missions.
After a fragmentation event, the debris is cast into orbits with different periods and inclination angles, and each orbit changes orientation at a different rate. Over time the orbits begin to spread out because of the variance in nodal regression rate. In the case of the Fengyun 1-C anti-satellite weapons test, since the debris was distributed across such a wide range of altitudes and orbital periods, the precession rates caused the fragments to envelope the globe and create a shell of orbiting debris in a short period of time, roughly 12 months [14]. Within one year, the orbital debris had almost completely encircled the Earth, clearly indicating the worldwide risk posed by fragmentation events.
Due to the nature of objects in Low Earth Orbit, one countrys orbital pollution contaminates space for the entire international community. Unlike geostationary orbit, where a satellite stays positioned directly above a single point on the Earths surface, the shorter periods of satellites in LEO result in them outpacing the Earths rotation. With all low orbiting objects encircling the entire globe, there is no way to only clear up the sky above a certain country.