Satellite collisions 'inevitable',warn space scientists

By Jon Swaine and Stephen Adams in London
Fri, Feb 13, 2009

Space scientists issued a stark warning yesterday over the "inevitable" prospect of more satellites crashing into each other after the first collision between two orbiting devices.

The crash between American and Russian satellites happened 485 miles over Siberia.

Russia's defunct Kosmos-2251, which weighed nearly a ton, and America's half-ton Iridium 33, which was part of the satellite telephone network, were both travelling at 25,200mph.

According to NASA, the Kosmos, which was launched in 1993, was out of control. The Iridium was put into orbit in 1997. British and American tracking stations believe that more than 500 sizeable pieces of debris -- bigger than 4in across -- were created by the crash.

They will add to thousands of fragments already orbiting the Earth.

Scientists gave warning that crashes in space would become more frequent, with Earth's orbit more crowded than ever. About 6,000 satellites have been launched since the USSR sent up Sputnik 1 in 1957 and about 3,000 remain in operation.

The collision risk is increased by the vast quantity of debris now in orbit. Last year, NASA estimated that there were 17,000 pieces of debris bigger than 4in, while the Space Security Index, a monitoring group, said there were more than 300,000 objects measuring between 0.4in and 4in and "billions" of even smaller fragments.

Even tiny objects pose a threat to manned space shuttles because they travel at such high speed.

Mark Matney, an orbital debris scientist at Johnson Space Centre in Houston, said of Tuesday's crash: "We knew this was going to happen eventually. Collisions will become more and more important in the coming decades."

Both the satellites were in a low, crowded orbit, said experts.

Patrick Wood, head of satellites at EADS-Astrium, Europe's biggest space company, said: "While newer satellites are being sent 22,000 miles up, most of the 17,000 space objects are in relatively low orbits, like these satellites were." (© Daily Telegraph, London)

- Jon Swaine and Stephen Adams in London