"A defunct NASA satellite the size of a bus that is expected to fall to Earth on Friday will likely miss North America, NASA said.

The agency's 13,000-pound (5,900 kg) Upper Atmosphere Research Satellite, or UARS, has been slowly tumbling from orbit since its mission ended in 2005. It is expected to re-enter Earth's atmosphere and break apart on Friday."

The UARS satellite played a historic role in investigating the atmospheric chemistry behind the stratospheric ozone hole, and has been replaced by more advanced instruments gathering additional data.

Irene Klotz reports for Reuters September 23, 2011. [2]