Huge Tumbling Satellite Could Fall to Earth Over US Tonight or Saturday, NASA Says (UPDATED)

A huge, dead satellite tumbling to Earth is falling slower than expected, and may now plummet down somewhere over the United States tonight or early Saturday, despite forecasts that it would miss North America entirely, NASA officials now say.

The 6 1/2-ton Upper Atmosphere Research Satellite (UARS) was expected to fall to Earth sometime this afternoon (Sept. 23), but changes in the school bus-size satellite's motion may push it to early Saturday, according to NASA's latest observations of the spacecraft.

"The satellite's orientation or configuration apparently has changed, and that is now slowing its descent," NASA officials wrote in a morning status update today. "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."

NASA expects about 26 large pieces of the UARS spacecraft to survive re-entry through Earth's atmosphere and reach the planet's surface. The biggest piece should weigh about 300 pounds. The spacecraft is the largest NASA satellite to fall from space uncontrolled since 1979.

Update:
http://www.space.com/13098-nasa-falling-satellite-uars-ocean-crash-site.html

NASA Pinpoints Pacific Ocean Grave of Fallen UARS Satellite

NASA and the military have pinned down exactly where and when a huge dead climate satellite fell to Earth on Saturday (Sept. 24).

The defunct Upper Atmospheric Research Satellite (UARS) re-entered the atmosphere at 12:01 a.m. EDT (0401 GMT) on Saturday, falling into the Pacific at 14.1 degrees south latitude and 189.8 degrees east longitude (170.2 west longitude), according to the Joint Space Operations Center at Vandenberg Air Force Base in California. NASA announced the new details today (Sept. 27).

These details close the case on NASA’s 6 1/2-ton UARS satellite, which was launched on a space shuttle in 1991 to study Earth’s ozone layer. The satellite was decommissioned in 2005, and has been slowly losing altitude since.

“Six years after the end of its productive scientific life, UARS broke into pieces during re-entry, and most of it up burned in the atmosphere,” NASA wrote in a final status update. “Twenty-six satellite components, weighing a total of about 1,200 pounds, could have survived the fiery re-entry and reach the surface of Earth.”

UARS’ final entry point places it in a “broad, remote ocean area in the Southern Hemisphere, far from any major land mass,” according to the NASA statement.

UARS debris could have scattered between 300 miles and 800 miles downrange, or generally northeast of the re-entry point.

“NASA is not aware of any possible debris sightings from this geographic area,” officials wrote.

Just after the UARS spacecraft’s plunge into the Pacific, NASA officials said it was likely the satellite was at the bottom of the ocean, but the exact location and time of its re-entry might never be known. But today, NASA announced that it had identified the satellite’s re-entry point.

NASA originally announced that UARS would fall back to Earth in an “uncontrolled re-entry” in late September or early October, and later refined the prediction down to the day. But no one could predict ahead of time exactly where or when the spacecraft would fall, because its trajectory depended on radiation from the sun and other varying conditions.

Even after the satellite came down, NASA could merely confirm that it had re-entered, most likely within 20 minutes of 12:16 a.m. EDT (0416 GMT), and probably over the Pacific Ocean. “We extend our appreciation to the Joint Space Operations Center for monitoring UARS not only this past week but also throughout its entire 20 years on orbit,” Nick Johnson, NASA’s chief scientist for orbital debris, at NASA’s Johnson Space Center in Houston, said in a statement. “This was not an easy re-entry to predict because of the natural forces acting on the satellite as its orbit decayed. Space-faring nations around the world also were monitoring the satellite’s descent in the last two hours and all the predictions were well within the range estimated by JSpOC.”

But other satellites will continue to fall. Late in October, or early in November, a German astronomy satellite is set to plunge uncontrolled back to Earth. While slightly smaller than UARS, the German satellite is expected to have more pieces survive re-entry, said McDowell, who worked on one of the instruments for it.

The German ROSAT satellite was launched in 1990, died in 1998, and weighs 2 1/2 tons. The German space agency figures 30 pieces weighing less than 2 tons will survive re-entry. Debris may include sharp mirror shards.

The German space agency puts the odds of somebody somewhere on Earth being hurt by its satellite at 1-in-2,000 — a slightly higher level of risk than was calculated for the NASA satellite. But any one individual’s odds of being struck are 1-in-14 trillion, given there are 7 billion people on the planet.

http://www.nwcn.com/home/?fId=130666...&fDomain=10202

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