By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - A European satellite that spent four years mapping Earth's gravity ran out of fuel on Monday and will plunge back into the atmosphere in about two weeks, officials said.
The Gravity field and steady-state Ocean Circulation Explorer, or GOCE, had been operating about 139 miles above Earth - lower than any other science satellite - to map variations in the planet's gravity.
"We have obtained the most accurate gravity data ever available to scientists," Volker Liebig, the European Space Agency's Earth observation programs director, said in a statement. "The outcome is fantastic."
With its onboard supply of xenon fuel depleted, GOCE will re-enter the atmosphere in about two weeks, the European Space Agency said on its website on Monday.
Most of the 1.2-ton (1,100-kg) satellite will burn up during its fiery descent. But up to 50 or so fragments - 25 percent of the spacecraft's mass - are likely to hit the ground or splash into an ocean.
"When and where these parts might land cannot yet be predicted, but the affected area will be narrowed down closer to the time of re-entry," the space agency said.
The uncertainty is due to constant changes in the upper atmosphere, which is strongly influenced by solar activity.
The agency will periodically update re-entry predictions and issue warning to populations if necessary, officials said.
With two-thirds of the planet covered by water and vast areas sparsely populated, the risk to human life or property is considered extremely low, they said.
In September 2011, NASA's 6.5-ton (5,900-kg) Upper Atmosphere Research Satellite plunged back to Earth, followed a month later by Germany's X-ray ROSAT telescope. Russia's failed 14-ton (12,700-kg) Phobos-Grunt Mars probe re-entered the atmosphere in January 2012.
NASA said that over the past 50 years, an average of one tracked piece of orbital debris fell back to Earth each day.
"No serious injury or significant property damage caused by re-entering debris has been confirmed," NASA said.
(Editing by Kevin Gray and Xavier Briand)