NASA satellite to crash land this week

A 20-year-old NASA satellite the size of a bus is heading towards Earth and is set to crash land later this week.

The US Department of Defence and NASA are tracking the six-tonne 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, 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.

Astronomy Ireland has said the satellite will pass over Ireland from west to southeast.

It said: "If the satellite re-enters the atmosphere over Ireland, it is likely to deposit debris along a path from Galway/Limerick/North Clare to Waterford/Wexford.

"Regions further away from this strip are unlikely to be affected should UARS re-enter over the country."

Chairman of Astronomy Ireland David Moore said: "Any re-entry over Ireland will take place in the early hours of the morning, with the exact time changing each day.

"On entry, the satellite will disintegrate as a result of friction and light up spectacularly in the sky, not unlike a fireball or very bright meteor."

NASA has stressed that the risk to human life and property from UARS is small.

In 50 years of space exploration no one has ever been hurt by falling space debris, while it is much more likely that a person will be killed by lightning, Mr Matney said.

UARS reached the end of its useful life in 2005, and NASA used up the satellite's remaining fuel to lower its orbit so it would come back to Earth sooner.

If the US space agency had not done so, the satellite still would have made an uncontrolled return at some point, possibly 20 years or more down the line, Mr Matney said.

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