Tomorrow, if all goes as predicted, NASA’s bus-sized Upper Atmospheric Research satellite (UARS) will fall back to Earth in some as yet to be determined location. Now, while NASA does not know exactly where the atmospheric re-entry will take place, the space agency has been able to begin the process of narrowing down the fall zone. So far, North America is out as the satellite is not expected to plunge anywhere over the continent.
So, what about the rest of the world? Short answer: NASA does not know yet.
While it may seem easy to make predictions as to where the UARS will fall, it is not as there are many variables that go into determining exactly where the satellite fall will take place.
First of all, solar activity has a lot to do with when the satellite will re-enter the atmosphere. Because space is, by and large, a vacuum, there is normally no drag on anything in orbit. However, when the Sun blasts energized atoms into space, these tiniest of all the universe’s building blocks can, together, create drag on the satellite like a headwind does to cars on Earth. Result: the UARS will slow down. In fact, it was a recent upsurge in solar activity that led the prediction for re-entry to be moved from Saturday to Friday. To complicate matters, solar activity remains high.
Another consideration: the shape and motion of the satellite. Right now, the UARS is going through an uncontrolled tumble as it orbits the Earth. Traveling at 17,500 mph as it enters the atmosphere, the UARS final destination can, at such speeds, be determined by the angle at which it enters the atmosphere, namely narrow or wide end first. After that, the nature of the breakup can further complicate trying to pin down exactly where the expected 1,200 pounds of debris will land.
Speaking of the risk to people and/or property, it is very, very small, with NASA giving a 1:3,200 chance of being hit by anything from the satellite. To further put one’s mind at ease, consider this: over 2/3 of Earth’s surface is water, which means, that there is a 2 of 3 chance that the remnants of the UARS will splash down harmlessly in some ocean.
In the end, the only way to know whether you live in the 500 mile debris fall zone is to keep an eye on NASA’s UARS page, which is being continuously updated as more information becomes available as the fall nears.
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