Satellites Destroyed in Orbital Collision - WSJ.com

"The Russian craft was being monitored by Pentagon organizations that keep track of space debris in order to prevent in-orbit collisions from damaging or destroying both commercial and government satellites. The National Aeronautics and Space Administration and the Pentagon track more than 10,000 separate pieces of high-speed debris, some barely a few inches in size.

Pentagon officials will face a barrage of questions about how they missed such an impending collision with an intact satellite, according to Tim Farrar, a satellite consultant familiar with Iridium. Commercial satellites are 'routinely repositioned to avoid potential collision with smaller pieces of debris,' said Mr. Farrar."