A large science satellite that mapped Earth's gravity, now doomed by the force, is heading back into the atmosphere, officials said on Saturday. Europe's Gravity field and steady-state Ocean Circulation Explorer, or GOCE, was just 99 miles (160 km) above Earth and dropping at a rate of 8 miles (13 km) per day, operations manager Christoph Steiger wrote in a status report posted on the European Space Agency's website.
"Re-entry into the atmosphere (is) probably less than two days away," Steiger said. The 1.2-ton (1,100-kg) satellite was launched in 2009 to map variations in Earth's gravity. Scientists assemble the data into the first detailed global maps of the boundary between the planet's crust and mantle, among other projects.
GOCE ran out of fuel on October 21 and has been steadily losing altitude since, tugged by Earth's gravity. Most of the spacecraft will burn up as it blasts through the atmosphere, but up to 50 fragments - or roughly 25 percent of the satellite - is expected to survive re-entry and end up somewhere on the planet's surface. With two-thirds of Earth covered by water and vast areas of sparsely populated land, the risk to human life and property is considered extremely low, the European Space Agency said.
Due to constant changes in Earth's upper atmosphere, scientists cannot yet predict where and when GOCE will re-enter. The last big satellite to fall back through the atmosphere was Russia's failed Phobos-Grunt Mars probe. The 14-ton (12,700-kg) spacecraft re-entered in January 2012. In 2011, NASA's 6.5-ton (5,900-kg) Upper Atmosphere Research Satellite and Germany's 2.4-ton (2,177-kg) X-ray ROSAT telescope re-entered.
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