Space junk coming to a street near you

[DJM83]

http://news.nationalgeographic.com/n...-five-science/

Traci Watson

for National Geographic News

Published September 9, 2011

It's coming from outer space.

Sometime in the next few weeks, pieces of a defunct NASA satellite will rain down on an unlucky patch of Earth.

Precisely where and when the space debris will hit home are not yet known, though the U.S. government will have a better picture of the so-called "debris footprint"—expected to be roughly 500 miles (805 kilometers) long—as the satellite's date with destiny draws near.

The doomed spacecraft, known as the Upper Atmosphere Research Satellite (UARS), was carried aloft by the space shuttle Discovery in 1991 to study Earth's atmosphere.

When the satellite was switched off in 2005, it became another piece of potentially hazardous space junk, so NASA nudged it toward Earth, aiming for a downward trajectory that would cause the craft to burn up in the atmosphere.

Now the satellite itself will become a type of experiment: Can an uncontrolled 6.3-ton object plummet out of orbit without hitting anybody?

At a press briefing Friday, NASA said there's generally little danger of death by space debris. Since the dawn of the Space Age some five decades ago, no human has been killed or even hurt by an artificial object falling from the heavens.

Many space objects experience a carefully controlled demise. Russia's Mir space station, for example, was steered into a remote patch of ocean in 2001. (Related: "Space Station to Fall to Earth—Find Out How and Where.")

But other pieces—old rocket segments jettisoned in orbit and abandoned spacecraft—fall toward Earth unguided. Last year one object a day, on average, made an unshepherded dive into the atmosphere, said NASA's Nick Johnson.

To date nearly 6,000 tons of human-made material have survived the fiery journey through our atmosphere, according to the Aerospace Corporation, a space-research center.