Some time around midnight eastern time on Sept. 23, a decommissioned NASA satellite fell out of the sky — but nobody knows where.

The Upper Atmosphere Research Satellite, or UARS, was launched in 1991. According to NASA, it was “the first multi-instrumented satellite to observe numerous chemical components of the atmosphere for better understanding of photochemistry.”

NASA powered off UARS in 2005 and for six years it continued to orbit as a piece of space junk, inching closer and closer to Earth.

On Sept. 21 NASA released information that stubborn UARS was finally nearing the atmosphere and should re-enter soon.

The story of the bus-sized, 12,500-pound, out of control satellite instantly made international news.

Most of the satellite was designed to break apart and burn up as it travelled through the atmosphere. But 26 components, weighing a total of 1,200 pounds, were actually expected to hit the surface, the biggest piece of which weighed more than 300 pounds, and would easily be hazardous to any populated area.

“The precise re-entry time and location of debris impacts have not been determined,” said the official NASA report. “During the re-entry period, the satellite passed from the east coast of Africa over the Indian Ocean, then the Pacific Ocean, then across northern Canada, then across the northern Atlantic Ocean, to a point over west Africa.”

Hundreds of photos and videos taken by skywatchers were uploaded to YouTube and Twitter, many gaining popularity overnight and showing some sort of falling debris.

However, the space agency has not confirmed any sightings. On Saturday, NASA chief scientist for orbital debris Nicholas Johnson said that it likely landed in the Pacific, a good distance from the Western coast of the United States and Canada.

“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 Johnson. “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.”

NASA said the odds of anyone being injured by the UARS debris were roughly 1 in 3,200, which is about three times greater than what they consider safe.

Since the launch of UARS, NASA and many other space agencies have implemented guidelines saying that all satellites must have, at most, a one in 10,000 chance of injury on re-entry.

Ted Llewellyn, professor of physics and engineering physics at the University of Saskatchewan, said that the re-entry of an out of control satellite is not all that unusual.

“It’s natural for satellites to drag,” said Llewellyn. “It’s the same with any atmosphere. The thing is basically a bus. What nations try to do now is use remaining fuel to get a dead satellite as high up as possible, so it can stay in orbit forever.”

Professor Llewellyn was actually involved with UARS, having done research using an instrument on the satellite called the Wind Imaging Interferometer, or WINDII. The instrument measured the temperature and wind speed of the atmosphere up to 300 kilometres high.

“It’s the same [as the wind at ground level]. It just blows in different ways.”

Llewellyn also pointed out a few more U of S connections to WINDII. Saskatchewan native Gordon Shepherd, now with York University in Toronto, did extensive work with ground-based interferometers at the U of S during the 1960s alongside Ronald Hilliard, another U of S alum.

At York, Shepherd went on to play an important role in the WINDII project, starting in 1984.

Further, the satellite was partially constructed by SED Systems in the 1980s, an aerospace firm located right here on campus.

As of now, there are roughly 22,000 pieces of space junk in orbit around Earth. However, there has been only one recorded injury due to a satellite re-entering the atmosphere. It happened in 1979 in Western Australia, when a piece of America’s SkyLab space station killed a cow.

With files from Daryl Hofmann/The Sheaf.

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Photo: NASA