UPDATE: Mystery solved.
NASA said Tuesday that new calculations "show the 20-year-old satellite entered Earth's atmosphere generally above American Samoa. But falling debris as it broke apart didn't start hitting the water for another 300 miles to the northeast, southwest of Christmas Island, just after midnight EDT Saturday," according to the Associated Press.
"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."
UPDATE Monday, Sept. 26: Well, the feared death from above never came, and the large UARS satellite many were worried about didn't make much of a splash on its return to Earth -- at least that anyone can tell.
NASA says that debris from the bus-sized satellite crashed into the surface early Saturday morning (EDT) and that its best guess for the location of impact lies somewhere in the Pacific Ocean. But because the agency doesn't know exactly when the satellite entered the Earth's atmosphere, it can't determine for certain exactly where the wreckage would have landed, Reuters reports.
Analysts say the 13,000 pounds of debris, which would have broken up into many pieces while moving through the atmosphere but was likely still made of large and potentially dangerous chunks, has yet to be reported or found -- and it will likely stay that way for the foreseeable future.
"Because we don't know where the re-entry point actually was, we don't know where the debris field might be," Nicholas Johnson, chief orbital debris scientist at NASA's Johnson Space Center in Houston, told Reuters. "We may never know."
UPDATE Friday, Sept. 23 at 12:37 p.m.: The six-ton satellite falling to Earth isn't moving as fast as NASA originally thought and there is now an ever-so-slight chance it could hit the U.S. after all.
The space agency had predicted a Friday morning or afternoon (EDT) impact, but scientists now say that the 20-year-old climate satellite -- or at least what's left of it after the re-entry burn -- will likely make impact with the Earth's surface either late Friday or early Saturday morning.
NASA says that solar activity is no longer the major factor influencing the satellite's rate of descent. Instead, it has been slowed by an apparent change in its orientation or configuration. While the agency had previously said that the satellite would not be over North America when it crashed, the new speed appears to change the math somewhat. There is now a "low probability" any of the surviving wreckage will land in the U.S., NASA says. While the odds are still in Americans' favor, the agency warns: "the possibility cannot be discounted because of this changing rate of descent."
The New York Times:
The six-ton satellite circles the Earth on a tilted orbit, and as the planet turns each day, different locations pass underneath. The satellite’s orbit on Friday afternoon will not take it over any part of North America, but by Saturday, parts of the United States will again be in its path.
And the Washington Post with a touch more :
On Friday morning, the satellite was only 100 miles up, NASA said. It is steadily losing speed and altitude. When it’s about 42 miles above the surface, it will probably break up as the aluminum frame melts away, said Bill Ailor, an Aerospace Corp. engineer who has been monitoring the satellite.
UPDATE #2/Thurs. 1:07 p.m.: An amateur astronomer in France managed last week to capture images of the 20-year-old satellite during its slow plummet from orbit, the BBC reports.
The images are rather grainy, but they nonetheless appear to show the 6.5-ton satellite rotate as it falls to Earth.
The astronomer, Thierry Legault, recorded the images on Sept. 15 with the help of a 14-inch telescope that he attached to his camera.
You can view the rather grainy footage below, or check out more on Legault's Astrophotography site.
UPDATE #1/Thurs. 9:47 a.m.: Some good news for those Americans who are convinced that the 20-year-old satellite tumbling toward Earth is destined to land squarely on their house: NASA says the space debris won't crash anywhere in North America.
While the space agency can't say for certain where in the world the Upper Atmosphere Research Satellite (UARS) will crash, NASA said that they had narrowed down the impact window to sometime Friday afternoon (Eastern Daylight Time). At that time, the 6.5-ton satellite won't be passing over North America, according to the latest projections.
"It is still too early to predict the time and location of re-entry with any more certainty, but predictions will become more refined in the next 24 to 36 hours," NASA said in a statement early Thursday.
Meanwhile, space observers say that it's not only North Americans who have nothing to fear.
"The UARS reentry hazard is being overhyped," said Don Kessler, a retired NASA senior scientist for orbital debris research, told the Los Angeles Times.
The paper explains:
Calm down, satellite watchers say. Stuff falls from the sky every day; big stuff — larger than 1,000 pounds and thus weighty enough to generate debris that falls to the ground — falls about once a week.
The satellite is expected to partially burn up during reentry, but plenty of space souvenirs will likely survive. Scientists predict the satellite will break into about 100 pieces, with about a quarter of them likely to remain after the re-entry burn. The largest surviving piece could weigh as much as 300 pounds. Given the makeup of the Earth's surface, though, the chunks are most likely to land with a splash.
POST Monday, Sept. 19: A 20-year-old satellite is expected to crash into Earth later this week, and the debris has a roughly 1-in-3,200 chance of hitting a person, NASA officials say. (To be clear: that's the odds that any of the wreckage will hit any of the planet's 7 billion people, not the odds of hitting any specific person.)
NASA’s current projections show that the Upper Atmosphere Research Satellite – or UARS (pronounced: YOU-arz) if you want to sound cool – will finally succumb to the Earth’s gravity in the next several days, with an expected impact on Friday.
But, as the Washington Post explains, even actual rocket scientists can’t say for certain when – or where – impact will occur:
Out-of-control crashing satellites don’t lend themselves to exact estimates even for the precision-minded folks at NASA. The uncertainty about the “when” makes the “where” all the trickier, because a small change in the timing of the reentry translates into thousands of miles of difference in the crash site.
NASA officials have said that the drop zone for the UARS could be anywhere between the latitudes of northern Canada and southern South America, an area that includes pretty much the entire planet. Still, they say that the chances that someone will be injured during the impact is extremely remote and that, most likely, the satellite will land with a splash in a body of water, according to Space.com.
The satellite is expected to partially burn up during reentry, but plenty of space souvenirs will likely survive. Scientists predict the satellite will break into about 100 pieces, with about a quarter of them likely to remain after the re-entry burn. The largest surviving piece could weigh as much as 300 pounds.