China Tests Anti-Satellite Weapon
statement by David Wright, co-director of the Global Security Program at the Union of Concerned Scientists
"China's January 11, 2007 test of a kinetic energy anti-satellite (ASAT) weapon apparently destroyed a defunct Chinese satellite by slamming into it.
The Chinese satellite that was destroyed had a mass of 750 kilograms and was orbiting at an altitude of 850 kilometers. The collision would be expected to completely fragment the satellite into millions of pieces of debris: nearly 800 debris fragments of size ten centimeters or larger, nearly 40,000 debris fragments with size between one and ten centimeters, and some 2 million fragments of size one millimeter or larger. At the very high speeds these debris particles would have, particles as small as one millimeter can be very destructive. While shielding on satellites can help protect against small particles, most satellites do not carry such shielding. Moreover, shielding is not effective against debris larger than about one centimeter in size.
"The altitude of this test was of particular concern for two reasons. First, because of the low atmospheric density at that altitude, half of the debris larger than one centimeter would remain in orbit for a decade or longer. Moreover, the orbital region around 900 kilometers is very heavily used by satellites for both civil and military uses, which are threatened by the added debris.
"The Chinese test was similar to the U.S. test of a kinetic energy ASAT weapon that destroyed a U.S. scientific satellite in September 1985, the last time such a test was conducted by any country. The U.S. test took place at 525 kilometers altitude."