Look out below! Dead satellite could fall anywhere from Hudson Bay to Argentina

NASA is predicting that a dead satellite, once used to measure ozone levels, will fall to earth sometime late Friday or early Saturday morning.

The satellite is now slowing its descent, according to the latest NASA update. But it is still too early to predict the time and or the location of the re-entry of the Upper Atmosphere Research Satellite (UARS) with any certainty.

Solar activity is no longer a major factor in the satellite’s rate of descent, the NASA website states. The satellite’s orientation or configuration apparently has changed, and that is now slowing its descent.

It is unlikely that any debris that survives re-entry will land in the United States, but the possibility cannot be discounted because of this changing rate of descent, the NASA website stated.

Much will depend on “solar flux and the spacecraft’s orientation as the orbit decays,” Beth Dickey, a spokeswoman for NASA, said in an email to the Star. And both keep changing.

Equally difficult to predict is where the debris from the satellite will land, she said. But NASA officials have some clues.

Because the satellite’s orbit is inclined 57 degrees toward the equator, NASA scientists believe it will fall somewhere between 57 degrees North latitude and 57 degrees South latitude, she said. That would be a band around the Earth running roughly from the middle of Hudson Bay to the southern tip of Argentina — or most of the inhabitable area of the planet.

NASA officials say they will be able to pinpoint a more exact location — give or take some 10,000 kilometres — within two hours of the satellite’s re-entry.

“It’s potentially like a big orange school bus, travelling seven kilometres per second,” said Michel Doyon, manager of flight operations for Satellite Operations at the Canadian Space Agency, in an interview with the Star.

Although much of the satellite will burn up as it re-enters the atmosphere, about 500 kilograms will survive and crash to the Earth, including a portion of the satellite’s main chassis, Doyon said.

But Dickey said there is no reason for anyone to panic.

“Re-entries happen fairly frequently and there have been no reported injuries to date (that is, in the entire history of the Space Age),” she writes.

According to NASA, almost 400 catalogued objects — about 75 tonnes of spacecraft and rocket bodies — have re-entered the Earth’s atmosphere in an uncontrolled manner.

The risk of human injury from the UARS debris is one in 3,200, said Dickey.

“The risk of a specific individual being hurt by UARS debris is minuscule — one in trillions,” she said.

UARS was launched in 1991 from the space shuttle. It was the first multi-instrumented satellite to observe the chemical makeup of the atmosphere, focusing on ozone levels.

UARS data was designed to address many of the serious questions arising over ozone depletion and climate change. And it was helped in its mission by a Canadian-French instrument known as WINDII — more properly known as a wind imaging interferometer, Doyon said.

Designed at the Centre of Research in Earth and Space Science at York University, it was only expected to last 18 months but the instrument ended up working for 10 years.

“It’s a good made-in-Canada instrument,” he joked.

Its role was to study how wind travelled around the earth from 80 to 300 kilometres above ground.

“It provided an enormous quantity of information for scientists to model climate change and global warming,” Doyon said.

UARS — which is 10.7 metres long and 4.5 metres wide and weighs 5.4 tonnes — was designed to last only three years, but it remained in commission until December 2005.

If NASA had left UARS in orbit, it would have become a “huge piece of space junk orbiting the earth,” said Doyon. “And it could have harmed active new satellites and created more debris and more problems.”

In the coming decade, three more satellites will make uncontrolled entries into the Earth’s atmosphere. The next one is expected in April 2014.

NASA estimates 26 pieces of UARS will survive re-entry. There’s nothing toxic on the spacecraft, but the agency is still asking people to stay away from any debris. The reasons: the pieces may have sharp edges that could cut someone, and they are property of the U.S. government.

September 23, 2011 Post Under News update - Read More

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