UPDATE: Military tracking 6.5 ton piece of NASA space junk tumbling toward Earth

NASA’s de-orbiting satellite expected to hit Earth’s atmosphere today, track still unknown

nasa uars
The US Strategic Command's Joint Space Operations Center is tracking the 6.5 ton NASA Upper Atmosphere Research Satellite, or UARS that is expected to break up and pass through the Earth's atmosphere today.

If the satellite doesn't incinerate when it enters Earth's atmosphere, NASA officials expect to see 25 or 26 pieces of debris from the craft with the biggest piece is estimated to weigh 300 pounds, the Air Force says.

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NASA's most recent update on the break-up of UARS says (UPDATED): "As of 10:30 a.m. EDT on Sept. 23, 2011, the orbit of UARS was 100 miles by 105 miles (160 km by 170 km). Re-entry is expected late Friday, Sept. 23, or early Saturday, Sept. 24, Eastern Daylight Time. Solar activity is no longer the major factor in the satellite's rate of descent. The satellite's orientation or configuration apparently has changed, and that is now slowing its descent. There is a low probability any debris that survives re-entry will land in the United States, but the possibility cannot be discounted because of this changing rate of descent. It is still too early to predict the time and location of re-entry with any certainty, but predictions will become more refined in the next 12 to 18 hours."

No model exists to analyze or predict where the debris will fall, because there's no way to predict how the object will break up upon re-entry. So to get the best possible assessment, the Joint Space Operations Center started issuing reports to NASA four days before the expected re-entry, reporting more regularly as the satellite gets closer to Earth, the Air Force said

"The center will advise NASA when the satellite is two hours out from re-entering the Earth's atmosphere, give or take 15 minutes," said Air Force Maj. Michael Duncan, deputy chief of space situational awareness at the center in a statement. "Those 15 minutes could mean the difference of 7,000 miles [in distance] and where it penetrates the Earth's atmosphere."

Something of this size happens about once every year, but about once a week the center has an object that's usually a rocket body or something larger that's re-entering the Earth, the Air Force said.  The center, part of the Joint Functional Component Command for Space at Vandenberg Air Force Base, is responsible for tracking 22,000 objects -- mostly space junk.

NASA is confident the disintegration won't hit people or anything else. "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."

NASA's UARS satellite was launched in 1991 from the Space Shuttle and as the first multi-instrumented satellite to observe numerous chemical make-up of the atmosphere with a goal of better understanding atmospheric photochemistry, NASA stated.

Follow Michael Cooney on Twitter: nwwlayer8  

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