NASA’s decommissioned Upper Atmosphere Research Satellite (UARS) hit the Earth last night.

NASA’s Upper Atmosphere Research Satellite UPDATES: “The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite entered the atmosphere over the North Pacific Ocean, off the west coast of the United States. The precise re-entry time and location of any debris impacts are still being determined. NASA is not aware of any reports of injury or property damage.” NASA wrote at 2:37 p.m. EDT (6:37 p.m. UTC).

UPDATE: “Because of the satellite’s orbit, any surviving components of UARS should have landed within a zone between 57 degrees north latitude and 57 degrees south latitude. It is impossible to pinpoint just where in that zone the debris landed, but NASA estimates the debris footprint to be about 500 miles [804.7 kilometers] long.”

UPDATE: “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,” said Nick Johnson, NASA’s chief scientist for orbital debris, at NASA’s Johnson Space Center in Houston. “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.”

UPDATE: “DoD’s Joint Space Operations Center at Vandenberg AFB, CA, has assessed that NASA’s Upper Atmosphere Research Satellite reentered the atmosphere sometime between 0323 and 0509 GMT on 24 September. During this period the satellite passed over Canada, the African continent, and the Pacific, Atlantic and Indian Oceans. The mid-point of that ground-track and a possible reentry location is 31 N latitude and 219 E longitude.”

The $750 million satellite, weighing six tons, first penetrated Earth’s atmosphere somewhere over the Pacific Ocean, but that doesn’t necessarily mean it all fell into the sea, said NASA and the U.S. Air Force’s Joint Space Operations Center.

“NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday [3:23 a.m UTC Saturday], Sept. 23 and 1:09 a.m. EDT [05:09 a.m. UTC Saturday] Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite penetrated the atmosphere over the Pacific Ocean. The precise re-entry time and location are not yet known with certainty,” NASA said.

NASA's satellite "penetrated the atmosphere over the Pacific Ocean". Where the satellite landed is not known precisely yet.

NASA’s earlier calculations had predicted that the former climate research satellite, launched in 1991, would fall over a 500 miles (804.7 kilometers) swath and could include land.

The plummet began over the ocean and there was a lack of reports of people being hit, “gives us a good feeling that no one was hurt,” but officials didn’t know for certain, Steve Cole, NASA spokesman, told The Associated Press.

“In the entire 50-plus-year history of the space program, no person has ever been injured by a piece of re-entering space debris. Keep in mind we have bits of debris re-entering the atmosphere every single day.” said Mark Matney,  orbital debris scientist at NASA.

There were hypotheses on the Internet and Twitter, much of them centered on unconfirmed reports and even video of debris over Alberta, Canada.

That was possible because the last track for the satellite included Canada, starting north of Seattle and then in a large arc north then south, Steve Cole said. The track continued through the Atlantic south toward Africa, but it is hard to belive that satellite got that far if it started falling over the Pacific.

The surviving chunks of the satellite  include titanium fuel tanks, beryllium housing and stainless-steel batteries and wheel rims.

“No consideration ever was given to shooting it down,” NASA said.

The craft contains no fuel and so is not expected to explode on impact, and NASA also said on Twitter that talk of  “flaming space debris” was a “myth“.

“Pieces of UARS landing on earth will not be very hot. Heating stops 36km up, cools after that,” NASA said. The satellite contains nothing radioactive but its metal fragments could be sharp.

The U.S. space agency has warned anyone who comes across what they believe may be the satellite’s debris not to touch it but to contact authorities for assistance.

“Any pieces of UARS found are still the property of the country that made it. You’ll have to give ’em back to U.S.” NASA wrote on Twitter.

 “Should the public come across debris they believe to be from the downed satellite, they should alert the authorities, or the authorities may come after them.” said Robert Pearl, space artifacts expert .

Some lucky sky-watchers in Florida were able to catch a glimpse of the defunct satellite as it circled the Earth before its final descent.

NASA awaits more details from the Air Force, that was responsible for tracking debris, but where the satellite might have fallen, officials could never know precisely.

“Most space debris is in the ocean. It’ll be hard to confirm,” Steve Cole said.

The chart shows the predicted entry of the satellite point, based on data from U.S. Strategic Command.(William Harwood/MacDoppler Pro)

The satellite had 35 feet (10.7 meters) and some 26 fragments of the satellite representing 1,200 pounds (544.31 kilograms) of heavy metal had been expected to fall down. The biggest surviving chunk should be no more than 300 pounds (136 kilograms).

Space law professor Frans von der Dunk from the University of Nebraska-Lincoln told AFP that the US would likely have to pay damages to any country where the debris falls.

“Liability for damage caused by space debris is regulated by a 1972 international treaty that the U.S. has signed on to,”NASA wrote on Twitter.

The Upper Atmosphere Research Satellite is the biggest NASA spacecraft to crash back to Earth, uncontrolled, since the Skylab space station and the Pegasus 2 satellite (1979).

Russia’s 135-ton Mir space station hit the Earth in 2001, but it was a controlled dive into the Pacific.

No one had ever been hit by falling space junk and NASA expected that not to change. NASA put the chances that somebody somewhere on Earth would get hurt at 1-in-3,200, a person’s odds of being struck were estimated at 1-in-22 trillion, since there are 7 billion people on the planet.

The Upper Atmosphere Research Satellite ran out of fuel in 2005, it was built and launched before NASA and other nations started new programs that prevent this type of uncontrolled crashes of satellite.

“It was the first multi-instrumented satellite to observe numerous chemical components of the atmosphere for better understanding of photochemistry. UARS data marked the beginning of many long-term records for key chemicals in the atmosphere. The satellite also provided key data on the amount of light that comes from the sun at ultraviolet and visible wavelengths,” Beth Dickey and Steve Cole wrote.