Defunct NASA satellite falling back to Earth this week

NASA said on Monday that it expects a defunct science satellite to re-enter Earth's atmosphere on Friday.

The Upper Atmosphere Research Satellite, or UARS, has been inoperative for almost six years. Reuters reports that UARS was put in orbit during a space shuttle mission in 1991, and it collected measurements of ozone and other chemicals in the atmosphere for the next 14 years. Since 2005, it has slowly been losing altitude due to Earth's gravity.

"Although the spacecraft will break into pieces during re-entry, not all of it will burn up in the atmosphere," NASA said in a blog post. "The risk to public safety or property is extremely small, and safety is NASA's top priority. Since the beginning of the Space Age in the late-1950s, there have been no confirmed reports of an injury resulting from re-entering space objects. Nor is there a record of significant property damage resulting from a satellite re-entry."

According to Reuters, scientists expect up to 26 pieces of UARS, weighing a combined 1,100 pounds, to survive re-entry. NASA put the chances of debris hitting a person at one in 3,200. The debris will most likely land in an ocean or in an uninhabited land area.

It is not possible to predict just where the debris will land. But because the satellite's orbit, NASA estimates the debris footprint will be about 500 miles long. As of Monday afternoon, UARS was in a 130 mile by 143 mile orbit around the planet. Re-entry could also happen Thursday or Saturday.

On the off chance that you come across a piece of UARS, NASA has some advice.

"If you find something you think may be a piece of UARS, do not touch it," the agency said in a blog post. "Contact a local law enforcement official for assistance"