Thursday, September 22, 2011

UARS: Big Satellite, Little Reason for Worry

NASA's UARS satellite will probably fall back to Earth tomorrow.

The Upper Atmospheric Research Satellite (UARS) has been in the news a lot as of late, not for anything it's discovered, but for what it will soon be doing: making an uncontrolled plunge through Earth's atmosphere and, in all probability, surviving the complete descent in the form of 26 components weighing a combined total of nearly 1,200 pounds. The kicker: NASA has no idea where the500 mile stretch of debris will land until about 2 hours before the satellite's death plunge begins.

For people not familiar with space exploration, there is obviously a bit of concern as, after all, over 1,000 pounds of satellite parts will rain back down to Earth. Needless to say, if it were to hit someone or something, chances are that a part of the UARS would do a lot of damage. So, is there reason for one to worry?

According to NASA, not really.

In the 50+ years of the space age, no one has ever been hit by part of a falling satellite and no piece of property has ever sustained serious damage from such a fall, which should be cause for comfort as some really big things have come back down to Earth in an uncontrolled manner all the way from orbit.

It was way back in 1979 that the granddaddy of all uncontrolled satellite re-entries took place: the fall of the Skylab space station.

Launched in 1973 aboard a modified Saturn V rocket, Skylab was the first true space station in the modern sense of the word (the Russians launched a couple of tiny ones previously, but these were essentially one-man campers in orbit). Far bigger than anything ever put into orbit before, Skylab was, at its time, in the vanguard of space exploration and the proving ground for the long-dreamed of scenario of building cities in space. Crewed by 3 teams of astronauts throughout the mid 70s, the Skylab missions grew ever-longer in duration as astronauts set new space endurance records for each day they were aboard.

Finally, though, in the late 70s, NASA decided to change direction and move onto the space shuttle program, which promised a fast, economical, and safe way into space. Its mission complete, a permanently-vacated Skylab floated around in orbit, a cosmic ghost town, until 1979 when the fuel keeping the satellite aloft by way of small rocket bursts was depleted, thus dooming Skylab to a fiery destruction in Earth's atmosphere.

Problem: despite putting millions upon millions of dollars into Skylab and its design, NASA apparently never gave any thought as to what would happen when the satellite fell from orbit.

Result: a worldwide frenzy.

As soon as it was announced that parts of Skylab would survive the complete descent to Earth's surface, people reacted in all sorts of ways. Naturally, most of the reaction was worry about being hit by falling Skylab parts. On the other hand, some enterprising individuals resolved to try and grab pieces of the fallen space station and then put them up for sale. In what was the biggest publicity stunt of the whole Skylab fall affair, the San Francisco Examiner offered a $10,000 bounty for the first verifiable piece of Skylab brought to their office (the prize went to an Australian).

In the end, though, the worry was for nothing as even something as large as Skylab, which shed a ton of debris on its way down, didn't produce a trail of destruction in its wake. The same could be said for the space shuttle Columbia, which broke apart on re-entry in 2003, killing all 7 astronauts aboard. The shuttle debris was so thick that it produced a very strong signal on Texas weather radars. Still, despite the vast amount of debris that fell to Earth, no one was hit and no property damaged.

Now, this is not saying that someone/something couldn't be hit by a piece of the UARS but, if past history is an indication, the chances of getting hit by a satellite part (NASA goes with 1:3,200 odds) are very, very small, as should be the reason for worry.

For more on UARS
NASA's UARS Update Page
North America out of the danger Zone
FEMA Braces for the Worst
Amazing Video of UARS Tumbling

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