The National Aeronautics and Space Administration's dead six-tonne satellite fell to the Earth early on Saturday morning, starting its fiery death plunge somewhere over the vast Pacific Ocean.
Details were still sketchy, but the United States Air Force's Joint Space Operations Centre and NASA say that the bus-sized satellite first penetrated the Earth's atmosphere somewhere over the Pacific Ocean. That doesn't necessarily mean it all fell into the sea. NASA's calculations had predicted that the former climate research satellite would fall over a 500-mile (800 km) area.
The two government agencies say the 35-foot satellite fell sometime between 1.23 a.m. (GMT) and 5.09 a.m. (GMT). NASA said it didn't know the precise time or location yet.
Some 26 pieces of the satellite representing 1,200 pounds (550 kg) of heavy metal were expected to rain down somewhere. The biggest surviving chunk should be no more than 300 pounds (135 kg).
The Upper Atmosphere Research Satellite (UARS) is the biggest NASA spacecraft to crash back to Earth, uncontrolled, since the Skylab space station and the Pegasus 2 satellite, both in 1979.
Russia's 135-tonne Mir space station slammed through the atmosphere in 2001, but it was a controlled dive into the Pacific.
Before UARS fell, no one had ever been hit by falling space junk and NASA expected that not to change.
NASA put the chances that somebody somewhere on Earth would get hurt at 1 in 3,200.
But any one person's odds of being struck were estimated at 1-in-22 trillion, given there are 7 billion people on the planet.
