By Ralph Ellis, CNN
updated 3:50 PM EST, Thu November 7, 2013
(CNN) -- A European satellite that ran out of fuel will start falling in the next few days, and fragments of the disintegrating 2,000-pound spacecraft are expected to strike the Earth's surface.
Nobody knows where or when the fragments will hit, but the European Space Agency has said the parts are likely to fall into the ocean or unpopulated areas. Potential spots will be narrowed down closer to re-entry, ESA said on its website.
Re-entry probably will occur Sunday or Monday, Rune Floberghagen, mission manager for the Gravity Field and Steady-State Ocean Explorer, better known as GOCE, told the New York Times.
GOCE was launched in 2009 to map variations in the Earth's gravity in 3D, provide ocean circulation patterns and make other measurements.
ESA's website said the satellite "became the first seismometer in orbit" in March 2011 when it detected sound waves from the earthquake that struck Japan.
GOCE was expected to fall much earlier but fuel consumption was less than expected. In August, the satellite's altitude was lowered to about 139 miles, lowest of any research satellites, to improve the accuracy of the information being gathered, ESA's website said.
GOCE ran out of fuel October 21. On November 4, ESA's website said the satellite was orbiting the Earth at 119 miles and the rate of descent would increase significantly in coming days.