It’s a scenario that space analysts have forecasted for years: With thousands of satellites in orbit, sooner or later two had to collide.

As first reported by CBS News, a defunct Russian communication satellite known as Cosmos 2251 collided on Tuesday with one of 66 satellites in the Iridium constellation, which is used for satellite telephones. Within 12 hours, the US Strategic Command, which tracks space objects, had seen over 600 pieces of debris created by the collision.

That’s not surprising considering these satellites weighed around 700 kg each and were travelling at 7.5 kilometres per second (a rifle bullet, by comparison, travels at around 1 kilometre per second). An analysis by David Wright, of the Union of Concerned Scientists, estimates that the number of debris pieces could easily stretch into the millions, with over a thousand posing a very real threat to other satellites.

Why didn’t anyone see it coming? Well apparently, calculations of collision scenarios (known as conjunction in the biz) are presently only performed on the most valuable of space objects, such as the shuttle and space station. ESA also does conjunction analysis for its operational satellites.

Coverage

Orbital Collision Was The Worst Ever – Aviation Week

U.S., Russian satellites collide in orbit – MSNBC

Image: Iridium satellite