Some 530 million people in North America are in the clear.
NASA and Air Force officials tracking the impending, uncontrolled atmospheric reentry of a 6.5-ton U.S. science satellite say the spacecraft will not be passing over the U.S., Canada or Central America when it makes a destructive plunge back toward Earth on Friday afternoon.
However, debris could fall anywhere else in areas that stretch from 57 degrees north latitude to 57 degrees south latitude -- roughly from northern Siberia to southern South America. NASA and the Air Force will not know exactly where until the fall toward Earth begins.
Decommissioned in late 2005, the Upper Atmosphere Research Satellite was deployed by astronauts aboard shuttle Discovery in September 1991. Analysts expect about 26 parts weighing a total of 1,200 pounds to survive reentry and hit the surface of Earth.
Odds of a single person being struck by falling debris: 1 in 3,200.
ABOUT THE IMAGE: Click to enlarge the NASA image of the UARS on the end of shuttle Discovery's robot arm before it was deployed in September 1991.