Scientists were trying to establish how and where a defunct research satellite returned to the Earth Sunday, after warning that some parts might survive re-entry and crash at up to 280 mph.
There was no immediate solid evidence to determine above which continent or country the ROSAT scientific research satellite entered the atmosphere, said Andreas Schuetz, spokesman for the German Aerospace Center.
Most parts of the minivan-sized German satellite were expected to burn up, but up to 30 fragments weighing a total of 1.87 tons could have hit the planet.
Citing officials, Space.com reported that ROSAT slammed into Earth's atmosphere sometime between 9:45 p.m. and 10:15 p.m. ET on Saturday.
Scientists were no longer able to communicate with the dead satellite and it must have traveled about 12,500 miles in the final 30 minutes before entering the atmosphere, Schuetz said.
Schuetz said it could take days to determine exactly where pieces of the satellite had fallen, but that the agency had not received any reports that it had hit any populated areas.
"We have no such information," he said Sunday.
Based on ROSAT's orbital path, these fragments could be scattered along a swath of the planet about 50 miles wide, German aerospace officials have said.
Scientists said hours before the re-entry into the atmosphere that the satellite was not expected to hit over Europe, Africa or Australia. According to a precalculated path it could have been above Asia, possibly China, at the time of its re-entry, but Schuetz said he could not confirm that.
The 2.69-ton scientific ROSAT satellite was launched in 1990 to study X-ray radiation from stars, comets, supernovas, nebulas and black holes, among other things. The satellite was originally designed for an 18-month mission, but it far outlived its projected lifespan. [Photos of Doomed ROSAT Satellite]
It retired in 1999 after performing the first all-sky survey of X-ray sources with an imaging telescope.
The largest single fragment of ROSAT that could hit into the earth is the telescope's heat-resistant mirror.
During its mission, the satellite orbited about 370 miles above the Earth's surface, but since its decommissioning it has lost altitude, circling at a distance of only 205 miles above ground in June for example, the agency said.
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.
Mission controllers initially estimated that ROSAT could fall to Earth in November, but increased solar activity caused the satellite's orbit to decay faster than originally expected. As the sun's activity ramps up, it heats up and expands the atmosphere, which creates more drag on satellites in orbit.
'Catch them' ROSAT's fall from space shone a spotlight on the growing problem of debris in space.
"One option is we want to be able to catch uncontrolled satellites in the future," Jan Woerner, head of the executive board of the German Aerospace Center, told Space.com. "We're working on such a mission to catch them, depending on their state, and have a controlled re-entry or send them to a graveyard, in order to prevent this situation in the future."
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 satellite fell over a 500-mile span.
The German space agency puts 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 are one in 14 trillion, given there are 7 billion people on the planet.