Pieces of a retired German satellite hurtling toward the atmosphere may crash to Earth this weekend, the German Aerospace Centre has said.
Scientists have honed their initial estimate of when the satellite would hit, from a span of four days to either Saturday or Sunday.
Parts of the satellite, which is the size of a minibus, will burn up during re-entry but up to 30 fragments weighing a total of 1.87 tons could crash into the Earth at up to 280mph.
The satellite orbits the Earth every 90 minutes, and scientists can only say that it could hit Earth anywhere along its path, between 53 degrees north and 53 degrees south - a vast swathe of territory that includes much of the planet outside the poles.
Another defunct satellite fell to Earth at the end of last month. The six-ton Upper Atmosphere Research Satellite was the biggest Nasa spacecraft to tumble out of orbit, uncontrolled, in 32 years.