A huge, dead satellite tumbling to Earth is falling slower than expected, and may now plummet down somewhere over the United States tonight or early Saturday, despite forecasts that it would miss North America entirely, NASA officials now say.

(Update Sept 23rd) “The satellite’s orientation or configuration apparently has changed, and that is now slowing its descent,” NASA officials wrote in a morning status update today. “There is a low probability any debris that survives re-entry will land in the United States, but the possibility cannot be discounted because of this changing rate of descent.”


Late Wednesday (Sept. 21), NASA predicted that the UARS satellite would not be over North Americawhen it finally plunged down to the Earth’s surface. That scenario has changed now that the 20-year-old satellite’s descent has slowed, the agency said.
But where the UARS spacecraft will fall still remains anyone’s guess. NASA orbital debris experts have said the satellite could fall anywhere between the latitudes of Northern Canada and Southern South America, a region of Earth that encompasses much of the planet.
“It is still too early to predict the time and location of re-entry with any certainty, but predictions will become more refined in the next 12 to 18 hours,” NASA officials wrote in the latest update.
Latest NASA Update (Sept. 22):   “As of 9:30 p.m. EDT Sept. 22, 2011, the orbit of UARS was 110 mi by 115 mi (175 km by 185 km). Re-entry is possible sometime during the afternoon or early evening of Sept. 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period. 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 hours.”

(Space.Com) For the latest news about NASA’s UARS spacecraft fall, visit: Falling NASA Satellite: Complete Coverage of UARS Spacecraft’s Fiery Demise.  A NASA satellite the size of a school bus is just hours away from taking a fiery plunge into Earth’s atmosphere and could set off a dazzling display when it does … if anyone is able to see it.
NASA’s 6 ½-ton Upper Atmosphere Research Satellite is due to fall somewhere on Earth Friday (Sept. 23), though exactly where and when remains a mystery.  As to when UARS is destined to come down, the best estimates right now seem to be focusing on an interval roughly 18 hours long, running from midday Friday to early Saturday.  Ted Molczan, the moderator of the SeeSat Internet mailing list, utilized six sets of orbital elements obtained from the U.S. Strategic Command to derive a possible window for re-entry.  His calculations suggest that UARS could re-enter anytime from Sept. 23 at 1432 GMT (10:32 a.m. EDT) to Sept. 24 at 0648 GMT (2:48 a.m. EDT).

Another SeeSat member, Harro Zimmer of Berlin, Germany, predicts Friday at 2004 GMT (4:04 p.m. EDT) plus or minus five hours, and descending on 19.1 degrees north, 128.5 degrees east  ?over the West Pacific near the northwest coast of Japan.
Interestingly, if UARS is somehow still in orbit Friday evening, it is predicted to make up to three southwest-to-northeast passes over parts of North America. [Related: How to Spot Satellites]  NASA says Tracking and Impact Prediction messages (“TIPs”) will be prepared and released to the general public two days, one day, 12 hours, six hours and two hours ahead of the UARS re-entry. But even two hours before re-entry, the average time uncertainty amounts to 25 minutes for nearly circular orbits.
This works out to plus or minus 12,000 miles (19,300 km) on the Earth.
Keep in mind that only the track during the final revolution over the Earth can be forecast, and not the exact geographical location of the satellite’s burn-up. Unpredictable tumbling of any space vehicle as it collides with the denser air can alter the drag forces acting upon it or produce an aerodynamic lift that can deflect it from its projected path.
If you happened to be lucky enough to be within viewing range of a satellite that is re-entering the atmosphere, the sight, put simply, would amount to a short-lived but spectacular fireworks display. Unlike a fireball meteor, whose flight across the sky might take no more than a few seconds, a re-entering satellite’s path usually lasts much longer.

As the satellite descends to an altitude of about 50 miles (80 kilometers), friction with the atmosphere is converted to light and heat. As it moves on a relatively slow – one could almost use the adjective “majestic” – flight across the sky, what is usually seen is a long trail of light and sparks that can take on virtually every color of the rainbow. [Photos of NASA’s Huge Falling Satellite UARS]
Small chunks of the satellite may be seen to break off and trail behind the main body. (NASA expects up to 26 pieces from UARS to survive re-entry and reach the ground.) If the re-entry occurs at night, it could light up the sky with a brilliance that easily rivals the full moon. Even if it occurs during the daytime, the satellite’s fiery passage across the sky could be readily seen.
Notes veteran satellite watcher Kevin Fetter: “A nice sized [satellite] with a uncontrolled re-entry. What a nice light show it should put on, if the decay occurs where people can see it.”
LOS ANGELES (AP) — While North America appears to be off the hook, scientists are scrambling to pinpoint exactly where and when a dead NASA climate satellite will plummet back to Earth on Friday.
The 6-ton, bus-sized satellite is expected to break into more than a hundred pieces as it plunges through the atmosphere, most of it burning up.
But if you’re hoping for a glimpse, the odds are slim. Most sightings occur by chance because the re-entry path can’t be predicted early enough to alert people, said Canadian Ted Molczan, who tracks satellites for a hobby.
In all his years of monitoring, Molczan has witnessed only one tumble back to Earth – the 2004 return of a Russian communications satellite.
It “looked like a brilliant star with a long glowing tail,” he said in an email.
The best guess so far is that the 20-year-old Upper Atmosphere Research Satellite will hit sometime Friday afternoon or early evening, Eastern time. The latest calculations indicate it will not be over the United States, Canada and Mexico during that time.
Until Thursday, every continent but Antarctic was a potential target. Predicting where and when the freefalling satellite will land is an imprecise science, but officials should be able to narrow it down a few hours ahead.
While most of the satellite pieces will disintegrate, 26 large metal chunks – the largest about 300 pounds – are expected to survive, hit and scatter somewhere on the planet. With nearly three-quarters of the world covered in water, chances are that it will be a splashdown.

If the re-entry is visible, “it’ll look like a long-lived meteor,” said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
Since the dawn of the Space Age, no one has been injured by falling space debris. The only confirmed case of a person being hit by space junk was in 1997 when Lottie Williams of Tulsa, Okla., was grazed in the shoulder by a small bit of debris from a discarded piece of a Delta rocket.  (continue reading)