Almost 20 years to the day after it was launched into space to collect data on Earth's atmosphere and interactions with the sun, NASA's Upper Atmosphere Research Satellite is coming back home--in pieces--and there's a higher than normal chance one of them will hit someone.
But before you run to grab your diamond and titanium alloy umbrella that I know you have somewhere in the back of the hall closet for just such an occasion, it's important to note that there's only a 1 in 21 trillion chance that a piece of the space junk will hit you specifically, according to an AP report. A NASA scientist apparently told the AP that there is a 1 in 3,200 chance that a piece of the satellite will hit someone on Earth, which is much higher than the 1 in 10,000 threshold NASA has adopted as an acceptable risk. That rule was put in place after the UARS satellite was launched in 1991.
CNET attempted to confirm the figure, but NASA's East Coast media headquarters is closed for the day. We've reached out through other channels, but did not immediately receive a response. I called U.S. Strategic Command at Vandenberg Air Force Base in California, which also houses the Joint Space Operations Center that "works around the clock detecting, identifying, and tracking all manmade objects in Earth orbit, including space junk," according to a NASA release.
A communications officer there told me that she believed NASA had worked with another agency to come up with a risk model for the UARS re-entry. NASA often uses software called--in typical NASA naming style--ORSAT, for Object Re-entry Survival Analysis Tool, to figure these sorts of things out.