NASA has confirmed that its defunct 20-year-old Upper Atmosphere Research Satellite (UARS) fell to Earth in a remote part of the Pacific Ocean, and, most likely, no one witnessed the much-anticipated re-entry of its orbital debris.
It took a few days of detective work and calculations, but the U.S. space agency NASA has narrowed down the time and place UARS plummeted back to Earth.
Nick Johnson, chief scientist for orbital debris at NASA's Johnson Space Center in Texas, said the space agency is "very, very confident" that UARS re-entered the Earth's atmosphere at 0400 UTC September 24. He said it was in the general vicinity of Christmas Island, over a broad, remote expanse of ocean in the Southern Hemisphere, far from any major land mass. NASA says the debris could have fallen over an 800-kilometer area, generally northeast of the spot where it first hit the atmosphere.
"Because the re-entry of the UARS satellite took place over the mid-Pacific Ocean, it's unlikely that anyone actually observed the re-entry," Johnson. "We have not yet received any reports from passengers on airplanes, or passengers on naval vessels in the area or any of the small islands in the vicinity that would indicate anybody observed the debris."
NASA narrowed down when and where UARS re-entered by noting what space surveillance sensors around the world did not observe.
"One of the ways that we determine that a satellite has re-entered is by looking at sensors that have failed to detect a satellite which is predicted to come by," added Johnson. "So we looked for a number of sensors very soon after the 0400 hour GMT [UTC] and found that no sensors in the U.S. space surveillance network were able to observe the satellite after that time."
A total of 26 metal pieces of UARS, a bus-sized satellite, were expected to survive the fiery re-entry.