NASA said the satellite fell back to Earth between 8:23 p.m. and 10:09 p.m. PT. Experts at the El Segundo tracking center said people in the Los Angeles area were able to see the satellite around 7:40 p.m.
The satellite passed over the Atlantic, Pacific and Indian oceans, as well as Canada, Africa and Australia. However as of 12:30 a.m. Saturday, they have not confirmed the precise re-entry time and location.
"There is a tremendous amount of uncertainty in the analysis to tell us the exact impact point," said space debris expert Randy Kendall. "It is either flying over an ocean or sparsely populated areas. So we can't get a visual confirmation and we have to wait for strategic command to get a tracking update to tell us."
The research satellite, which is roughly the size of a small school bus, disintegrated as it made its way back into the Earth's atmosphere.
But 26 pieces were expected to rain down somewhere. Those pieces weighed anywhere between a few pounds to 300 pounds, according to Kendall.
/*NASA*/ said the chances of someone in the world getting hit by a falling satellite's debris are 1 in 3,200. But the odds of you personally getting hit are 1 in 21 trillion.
The satellite was launched on the back of the shuttle Discovery and has been orbiting Earth for 20 years. It will be the biggest NASA spacecraft to crash back to Earth, uncontrolled, since the post-Apollo 75-ton Skylab space station and the more than10-ton Pegasus 2 satellite, both in 1979.
This may not be the last time something like this happens. There are 20,000 pieces of space junk that the Air Force is currently tracking.
The Associated Press contributed to this report.