Satellite collision worries scientists

With over 6,000 satellites having been launched since1957 and with half that number no longer working and flying blind, it was only a matter of time that a collision occurred. Yesterday a redundant Russian military satellite struck a telecoms satellite belonging to US company Iridium. The incident took place some 780 km [485 miles] above Siberia destroying both orbiting satellites into thousands of pieces of debris.

The cost to Iridium is of course substantial, but there is further risk to other satellites in the wake of the collision. There are already millions of pieces of so-called space junk floating around the Earth, and each piece poses a risk for the expensive satellites in orbit. The current estimate is that there are over a million bits of debris orbiting the Earth. About 70,000 objects about the size of a postage stamp have been detected between 850 - 1,000 km above the Earth. In all this only around 12,000 manmade objects are tracked, but it is a virtually impossible task to predict when a collision might occur. Even when such a prediction is made it is often difficult to act in time. Although the debris is small the damage inflicted can be devastating. Below altitudes of 2,000 km, the average relative impact speed is 36,000 km/h [21,600 mph]. This incident only highlights the vulnerability of Earth’s high-tech space network of satellites. Major Regina Winchester, of the U.S. Strategic Command, said, "Space is getting pretty crowded. The fact that this hasn't happened before -- maybe we were getting a little bit lucky". That luck may well be running out [BBC / Sky News / CNN].