German X-ray space telescope falls back to Earth (UPDATED)

Editor's note...
  • Posted at 07:23 PM EDT, 10/21/11: Germany monitors path of falling X-ray satellite
  • Updated at 02:10 AM EDT, 10/22/11: Updated U.S. STRATCOM entry prediction
  • Updated at 11:45 PM EDT, 10/22/11: Satellite re-entry confirmed by German Aerospace Center
CBS News

Just one month after a decommissioned NASA science satellite fell to Earth, an out-of-service German space telescope plunged back into the atmosphere Saturday, according to the German Aerospace Center. Experts predicted much of the spacecraft's heat-resistant 1.7-ton X-ray mirror and carbon composite support structure would survive re-entry to hit the ground somewhere between 53 degrees north and south latitude, somewhere between the latitude of northern Europe and the tip of South America. But there was no immediate word on precisely where the satellite came down or whether any debris made it to the surface.

The nested mirrors at the heart of the ROSAT X-ray telescope. (Credit: German Aerospace Center)
Given the size of the planet, the vast oceans under the orbital track and low population density in remote areas, experts said the odds of a single individual somewhere in the world being injured were roughly 1-in-2000.

An artist's depiction of the Roentgen Satellite, or ROSAT, in orbit. (Credit: German Aerospace Center)
"Based on the latest studies, it is thought possible that up to 30 individual debris items with a total mass of up to 1.6 tons might reach the surface of the Earth," DLR, the German Aerospace Center, said in a web posting last week.

"The X-ray optical system, with its mirrors and a mechanical support structure made of carbon-fibre reinforced composite -- or at least a part of it -- could be the heaviest single component to reach the ground. In the event of fragments reaching the surface of Earth, they could be traveling at speeds of up to (280 miles) per hour."

U.S. Strategic Command radar tracking indicated the Roentgen Satellite, or ROSAT would re-enter the atmosphere late Saturday. At 10:45 p.m. EDT (GMT-4), the German Aerospace Center reported that ROSAT re-entered between 9:45 p.m. and 10:15 p.m.

"On Sunday, 23 October 2011, between 1:45 UTC (3:45 CEST) and 2:15 UTC (4:15 CEST) the German ROentgen SATellite ROSAT has re-entered Earth's atmosphere," DLR reported on its web site. "There is currently no confirmation if pieces of debris have reached Earth's surface."

Re-entry of NASA's 6.3-ton Upper Atmosphere Research Satellite, or UARS, generated headlines around the world after NASA space debris experts predicted up to 30 pieces of wreckage, the most massive tipping the scales at around 330 pounds, would survive atmospheric friction to hit the ground.

As it turned out, UARS fell harmlessly back to Earth over the Pacific Ocean Sept. 24. It is not known how much debris actually made it to the surface.

The 5,348-pound ROSAT, launched by NASA from Cape Canaveral, Fla., in 1990, ended its mission in 1999. It was not equipped with maneuvering thrusters and engineers had no way to control, or target, it's re-entry.

Even so, the likelihood of a injury or property damage "is extremely low," DLR said. Odds of 1-in-2000 mean that "one person is predicted to be injured for every 2000 de-orbit events of this kind."

U.S. STRATCOM tracks thousands of objects in low-Earth orbit, ranging in size from about four inches across to the football field-size 900,000-pound International Space Station.

Mark Matney, an orbital debris researcher at NASA's Johnson Space Center in Houston, said on average, one "tracked object" re-enters the atmosphere every day. Small satellites and rocket bodies re-enter once a week and large objects, such as UARS, fall to Earth about once a year.

"To our knowledge," he said, "there's never been an injury or significant property damage."