Here we go again: Another dead satellite heading our way

The German x-ray satellite ROSAT

WASHINGTON - As the immortal Yogi Berra is said to have observed, it's deja vu "all over again." A fitting phrase given today's news that in late in October, or early in November, a German astronomy satellite is set to plunge uncontrolled back to Earth.

This comes just days after the 20-year-old Upper Atmosphere Research Satellite known by its acronym UARS, entered Earth's atmosphere and plunged into the southern Pacific Ocean, bringing to a close a weeks-long drama annotated by increasingly worried guesswork by sundry astronomers who had little idea whether this 6.5-ton hunk of metal the size of a school bus would land on someone's head.

While slightly smaller than UARS - the craft weighs 2 ½ tons - the German satellite is expected to have more pieces that survive re-entry. The German ROSAT satellite, designed to study high-energy radiation was launched in 1990 and died in 1998. (The name is an abbreviation of the word Rontgensatellit. In German X-rays are called Rontgenstrahlen.) The German space agency figures 30 pieces weighing less than 2 tons will survive re-entry. Debris may include sharp mirror shards.

The German space agency puts the odds of somebody somewhere on Earth being hurt by its satellite at 1-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 1-in-14 trillion, given there are 7 billion people on the planet.

Fortunate stroke for NASA

If the Germans are as lucky as NASA, it will be an easy day at the office. NASA's satellite fell into what might be the ideal spot, about as far from large land masses as you can get, U.S. space officials said Tuesday. Indeed, new U.S. Air Force calculations put the 6-ton satellite's death plunge early Saturday thousands of miles from northwestern North America, where there were reports of sightings. Instead, it plunged into areas where remote islands dot a vast ocean.

NASA says those new calculations show the generally above American Samoa. But falling debris as it broke apart did not start hitting the water for another 300 miles to the northeast, southwest of Christmas Island, just after midnight EDT Saturday. Experts believe about two dozen metal pieces from the bus-sized satellite fell over a 500-mile (800 kilometer) span.

"It's a relatively uninhabited portion of the world, very remote," NASA orbital debris scientist Mark Matney said. "This is certainly a good spot in terms of risk." Scientists who track space junk couldn't be happier with the result.

"That's the way it should be. I think that's perfect," said Bill Ailor, director of the Center for Orbital and Reentry Debris Studies at the Aerospace Corp. "It's just as good as it gets."

Satellite has fallen to Earth, NASA says
CBS News: Bill Harwood's Space Place blog
NASA: UARS updates

On Saturday, scientists said it was possible some pieces could have reached northwestern Canada and claims of sightings in Canada spread on the Internet. But NASA said Tuesday that new calculations show it landed several minutes earlier than they thought, changing the debris field to an entirely different hemisphere.

"It just shows you the difference that 10 or 15 minutes can make," said Harvard University astrophysicist Jonathan McDowell, who tracks man-made space objects. On Saturday, he noted, "We were talking about, `Wow, did it hit Seattle?"'

NASA won't say how it knows the climate research satellite came in earlier, referring questions to the U.S. Air Force space operations center. Air Force spokeswoman Julie Ziegenhorn said better computer model reconstruction after the satellite fell helped pinpoint where the satellite - called the Upper Atmosphere Research Satellite returned to Earth - returned to Earth

After UARS was launched in 1991, NASA and other space agencies adopted new procedures to lessen space junk and satellites falling back to Earth. So NASA has no more satellites as large as this one that will fall back to Earth uncontrolled in the next 25 years, according to NASA orbital debris chief scientist Nicholas Johnson.