NASA bus-sized satellite to crash-land this week

WASHINGTON, September 21, 2011 (AFP) – What goes up must come down. But where?
That’s the big question when it comes to a 20-year-old NASA satellite the size of a tour bus which is careening toward Earth and set to crash-land later this week.

The US Department of Defense and NASA are tracking the six-ton spacecraft, which poses a one-in-3,200 risk of hitting one of the seven billion people on the planet, the US space agency said.

But experts admit they will not know much more until the final 20 or so minutes before it lands, with a predicted re-entry date of Friday, September 23, give or take a day.

“We know it is going to hit somewhere between 57 north latitude and 57 south latitude, which covers most of the inhabited world unfortunately,” said Mark Matney, an orbital debris scientist at the US space agency.

The Upper Atmosphere Research Satellite (UARS) was launched in 1991 to measure the ozone layer, wind and temperature. It was officially decommissioned in 2005.

It is the biggest NASA spacecraft to come back in three decades, after Skylab fell in western Australia in 1979, but Matney said similar-sized pieces of spent rocket and satellite debris fall to Earth rather frequently, given the global presence in