NASA's Upper Atmosphere Research Satellite (UARS) will fall to Earth sometime during late September or early October, NASA told reporters today in a teleconference. Atmospheric changes that take place on a daily basis making it impossible to predict exactly where or when it will come down with any real accuracy even as close as two hours prior to the re-entry.
Satellites the size of UARS, on average fall to Earth about once every year and are the subject of detailed break-up analyses by NASA scientists. In this case, NASA expects that UARS will break up in such a way that 26 pieces will strike the ground at speeds ranging from tens of miles per hour to hundreds of miles per hour, according to Nick Johnson of NASA's Orbital Debris Program. In fact, said Johnson, NASA has calculated the odds of any piece of the debris striking a person as 1 in 3200. A number which he says is very, very low and is simply based on the area of possible landfall and global population density.
The re-entry of UARS should be very visible even if it occurs in daylight said Johnson. However, it will b impossible to give enough advance information about where it will re-enter to advise people where and when to look for it. Based on the amount of water versus the amount of land in possible impact field, it is most likely that it will take place out over an ocean and may only be incidentally visible to passing aircraft or ocean vessels.
UARS made a number of important scientific observations over its 14 year effective lifespan including detailed measurement of Earth's atmosphere and of solar radiation. Since 2005, other satellites have replaced its full suite of observational capabilities.
Factbox:
* UARS was built in the 1980's and launched in 1991 at a total cost of $750 million.
* Intact, UARS masses 5.7 metric tons and completely fills the cargo bay of a space shuttle.
* Without NASA intervention, UARS would have remained in orbit until 2025, but its orbital decay was intentionally accelerated by using up all remaining onboard maneuvering propellants in 2005 when it had exhausted its scientific usefulness.
* UARS was the first satellite to record solar flux data over and entire 11 year solar cycle.
* The largest piece of UARS expected to reach the ground masses a little over 300 pounds.
* Other than being struck by fallen debris, NASA says, the biggest risk from the debris is a person getting cut by sharp edges if they try to handle the debris after is has landed. There are absolutely no toxic materials on board, according to Paul Hertz of NASA's Science Mission Directorate.
* All pieces of UARS remain the property of the U.S. government and their location should be made known to local law enforcement officials. Possession or sale of any of the debris by private individuals in the United States is illegal and subject to prosecution.
* In a typical year, 400 pieces of tracked man-made debris re-enters Earth's atmosphere.
* One piece of man-made space debris survives to reach the ground, on average, each week.
* In 2010, approximately 75 metric tons of man-made space debris fell from orbit Earth.
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Brad Sylvester writes about the space program for the Yahoo! Contributor Network. Watching the Apollo missions through the static on a small black and white television sparked a lifelong interest in the space sciences for him. Since then, he has spent 40 years watching improvements in the technologies of space travel and our understanding of the universe.
