By Allan Hall
Last updated at 6:29 PM on 10th October 2011
Earth has been told to brace for a possible satellite collision as an orbiting telescope weighing nearly three tons has spun out of control and is plummeting homewards.
ROSAT, a German X-ray telescope built with British and American technology, has been orbiting the Earth since 1990 and has provided invaluable data on stars. But they lost contact with it in 1999.
It is now predicted to re-enter Earth’s atmosphere at the end of this month.
The German Aerospace Center has warned that 30 ‘individual pieces weighing a total of 1.6 tons may reach the surface of the Earth’.
ROSAT’s heat-resistant mirror in particular may not burn up upon re-entry and falling debris may include razor-sharp shards.
However Professor Heiner Klinkrad of the European Space Agency assured: ‘Until now in the more than 50-years of space history not a single person has been harmed [by pieces of falling satellites].’
ROSAT was launched on June 1, 1990, from U.S. launch site Cape Canaveral for what was originally intended as an 18-month mission.
It actually operated for more than eight years, finally shutting down on February 12, 1999. It is now expected to hit the Earth at some point between now and December.
Odds are long of anyone being hurt, but emergency services in Germany are practicing drills to deal with debris injuries just in case – although there is no evidence that it will land there as opposed to anywhere else.
Last month the German space agency estimated that ROSAT has a 1-in-2000 chance of hitting someone – higher than the 1-in-3,200 odds Nasa gave for UARS, the last satellite to fall to Earth.
But any one individual’s odds of being struck are 1-in-14trillion.
Heiner Klinkrad, head of the Space Debris Office at the European Space Agency, said in a webcast posted on the German Aerospace Center’s website: ‘It is not possible to accurately predict ROSAT’s re-entry.
‘The uncertainty will decrease as the moment of re-entry approaches.
‘It will not be possible to make any kind of reliable forecast about where the satellite will actually come down until about one or two hours before the fact.’
Last month, Nasa’s six-ton, bus-sized Upper Atmospheric Research Satellite made its final fiery plunge into the Earth’s atmosphere.
Americans had been warned that the 20-year-old orbiter could cause injuries and damage to property as it dropped about two dozen pieces of debris on to Earth weighting up to 300lbs.
The satellite was far smaller than the 135-ton Russian space station Mir, which fell to Earth in 2001 or the 100-ton Skylab that fell in 1979.
So far this year, two large Russian rocket stages have also fallen to earth without inflicting any injury.
Mir fell into the South Pacific, while Skylab hit the Indian Ocean and parts of sparsely populated western Australia. Because two-thirds of the Earth is ocean, space debris usually hits water.
Nasa urged anyone who finds a piece of the UARS satellite not to touch i