The European Space Agency says its GOCE research satellite will crash to Earth on Sunday night or during the day on Monday. It says it cannot predict where the debris will hit. But it claims the small fragments that survive reentry are unlikely to cause any casualties.
GOCE -- which stands for Gravity field and steady-state Ocean Circulation Explorer -- was launched in 2009 to map the Earth's gravitational field. It ran out of fuel last month, ending the mission.
Since then, the satellite has been spiraling steadily downward. Scientists say the 1,100-kilogram (2,425-pound) satellite already has fallen to an altitude of about 105 miles and is coming closer every minute.
Once it reaches an altitude of 50 miles, the satellite will break apart and most of it will burn in the atmosphere.
However, the space agency says about 20 percent of the spacecraft's original mass could survive and reach the ground. That portion, totaling about 200 kilograms (440 pounds) will break up into dozens of small fragments, scattered over a wide area. Scientists have been unable to calculate where or exactly when the debris will hit.
The agency points out that in the history of space flight, no man-made space objects that have re-entered Earth's atmosphere have ever caused injury to humans. It claims people are 250,000 times more likely to win the lottery than to get struck by any debris from the satellite.