POSTED: 11:19 p.m. HST, Oct 22, 2011
LAST UPDATED: 07:01 a.m. HST, Oct 23, 2011
BERLIN >> Scientists were trying to establish how and where exactly a defunct German research satellite returned to the Earth on Sunday, after warning that some parts might survive re-entry and crash at up to 280 mph.
Most parts of the minivan-sized ROSAT scientific research satellite were expected to burn up, but up to 30 fragments weighing a total of 1.87 tons could have crashed.
But there was no immediate solid evidence to determine where exactly the satellite entered the atmosphere, indicating it did not hit a populated area, said Andreas Schuetz, spokesman for the German Aerospace Center.
The center said the satellite entered between 0145 and 0215 GMT Sunday (9:45 p.m. and 4:15 p.m. Saturday Hawaii time) and would have taken only 10 or 15 minutes to hit the ground.
Hours before the re-entry into the atmosphere the center said the satellite was not expected to hit over Europe, Africa or Australia. According to the satellite's predicted path, scientists estimated it could have been above Asia at the time of its re-entry.
Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said the satellite appears to have gone down over Southeast Asia.
Calculations based on data made available to scientists by the U.S. military indicate that it must have crashed somewhere between the Indian Ocean off the coast of Myanmar, further inland in Myanmar or as far inland as China, he said.
McDowell, an astrophysicist who tracks man-made space objects and who worked on one of ROSAT's instruments, said two Chinese cities with millions of inhabitants each, Chongqing and Chengdu, were in the satellite's projected path during the time window in which it must have crashed.
"But if it had come down over a populated area there probably would be reports by now," he told The Associated Press in a telephone interview.
Schuetz said it could take days to determine exactly where pieces of the satellite had fallen.
"I don't think that we'll have a confirmation of any sort today," he said, pointing out that it also took NASA several days to establish where one of its satellites had hit last month.
The 2.69-ton (2.4 m scientific ROSAT satellite was launched in Cape Canaveral, Florida, in 1990 and retired in 1999 after being used for research on black holes and neutron stars and performing the first all-sky survey of X-ray sources with an imaging telescope.
Even in the last days, the satellite still circled the planet every 90 minutes, making it hard to predict where on Earth it would eventually come down.
The largest single fragment of ROSAT that could hit into the earth is the telescope's heavy heat-resistant mirror.
"The impact would be similar to, say, an airliner having dropped an engine," said McDowell. "It would damage whatever it fell on, but it wouldn't have widespread consequences."
A dead NASA satellite fell into the southern Pacific Ocean last month, causing no damage, despite fears it would hit a populated area and cause damage or kill people. Experts believe about two dozen metal pieces from the bus-sized UARS satellite fell over a 500-mile span.
The German space agency put the odds of somebody somewhere on Earth being hurt by its satellite at one 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 were one in 14 trillion, given there are 7 billion people on the planet.
After NASA's UARS was launched in 1991, space agencies adopted new procedures to lessen space junk and satellites falling back to Earth.
NASA has said it has no more large satellites that will fall back to Earth uncontrolled in the next 25 years.
Most big satellites now have propulsion systems that allow a controlled re-entering into the Earth's atmosphere, and better software allows more precise predictions and monitoring, McDowell said.
"We are in a more risk-averse culture now. If you say there is a 1-in-3000 chance that it might hurt someone, in the 1990s a government agency might have said 'that's an acceptable risk,' but in 2010 that's not the case," he said.
The German space agency on ROSAT: http://bit.ly/papMAA