Russian and US satellites collide

February 13, 2009 The civilian communications satellite  and the defunct  military communications satellite   over  on Tuesday, according to. The satellites, each weighing in excess of 1,000 pounds, and traveling at approximately 17,500 miles per hour, collided 491 miles above the earth.

The Iridium satellite was launched in 1997, and the Russian satellite was a model. The American satellite is expected to be replaced within the coming month as Iridium will maneuver one of its in-orbit satellites to replace the lost unit.

Although the first such satellite crash in space, such an event has been long predicted. Nicholas Johnson, chief scientist of at the  stated, "We knew this was going to happen eventually and this is it — this was the big one."

While the and the  are at minimal risk, the event does raise concerns that the debris cloud could collide with other satellites in the region, triggering an exponentially growing series of collisions and debris known as an.

The of the  office is tracking the debris. The result of plotting analysis will be posted to a public website.