Pieces of a retired German satellite hurtling toward theatmosphere may crash to earth this weekend, the German Aerospace Center saidThursday.
Scientists have now honed their initial estimate of when thesatellite would hit from a span of four days to either Saturday or Sunday. Asit nears, they will eventually be able to estimate impact within a window ofabout 10 hours.
Parts of the satellite, which is the size of a minivan, willburn up during re-entry but up to 30 fragments weighing a total of 1.87 tons(1.7 metric tons) could crash into the Earth with a speed of up to 280 mph (450kph).
The satellite orbits the Earth every 90 minutes andscientists can only say that it could hit Earth anywhere along its path,between 53-degrees north and 53-degrees south — a vast swath of territory thatincludes much of the planet outside the poles.
Scientists are no longer able to communicate with the deadGerman satellite ROSAT, which was launched in 1990.
ROSAT was used for research on black holes and neutron starsand performed the first all-sky survey of X-ray sources with an imagingtelescope.
It was initially intended to only be active for 18 monthsbut due to its great scientific success it was retired more than eight yearslater, in 1999 when communications were lost.
Even if the control center still had contact with thesatellite, it has no engines so they would not be able to change itstrajectory.
Scientists are now working on developing new technology thatwould allow for a controlled destruction of satellites in space, or the captureof satellites to prevent them from crashing into the Earth. But it will takemany years for that technology to be implemented, the German Aerospace Center said.
As it stands, satellite debris hits the atmosphere almostevery week, but most burns up upon re-entry and pieces rarely hit the Earth.
The largest single fragment of ROSAT that could hit into theEarth is the telescope's heat-resistant mirror.
The satellite will re-enter the atmosphere at a speed of17,400 mph (28,000 kph).