A German satellite around the size of a car is speeding towards Earth, officials said today, due to re-enter the atmosphere later this month but with little idea where fragments could land.
The x-ray observatory, named ROSAT, is expected to return o Earth between October 20 and 25, travelling at a speed of around 28,000 kilometres per hour, the German Aerospace Centre (DLR) said in a statement.
"The latest studies reveal that it is possible that up to30 individual pieces weighing a total of 1.6 tonnes may reach the surface of the Earth," the DLR said in a statement on its website.
"The time and location of re-entry cannot be predicted precisely," added the agency, citing fluctuations in solar activity for the uncertainty.
The satellite could re-enter the atmosphere three days before or after this range, the DLR said, stressing there was very little danger to humans.
Last month, a bus-sized US satellite that hurtled unpredictably toward Earth crossed over Africa and the northern Atlantic before plunging into the Pacific Ocean off California, NASA said.
There were no sightings or reliable accounts of damage as the six-tonne Upper Atmosphere Research Satellite (UARS) fell from the sky.
German satellite, Earth, ROSAT, German Aerospace Centre
The old research spacecraft was targeted to crash through the atmosphere sometime Friday night or early Saturday, putting Canada and Africa in the potential crosshairs, although most of the satellite should burn up during re-entry. The United States wasn't entirely out of the woods; the possible strike zone skirted Washington state.
"It just doesn't want to come down," said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics.
McDowell said the satellite's delayed demise demonstrates how unreliable predictions can be. That said, "the best guess is that it will still splash in the ocean, just because there's more ocean out there."
Until Friday, increased solar activity was causing the atmosphere to expand and the 35-foot, bus-size satellite to free fall more quickly. But late Friday morning, NASA said the sun was no longer the major factor in the rate of descent and that the satellite's position, shape or both had changed by the time it slipped down to a 100-mile orbit.
"In the last 24 hours, something has happened to the spacecraft," said NASA orbital debris scientist Mark Matney.
On Friday night, NASA said it expected the satellite to come crashing down between 11:45 p.m. and 12:45 a.m. EDT Saturday. It was going to be passing over the Atlantic, Pacific and Indian oceans at that time, as well as Canada and Africa.
"The risk to public safety is very remote," NASA said in a statement.
Any surviving wreckage is expected to be limited to a 500-mile swath.
The Upper Atmosphere Research Satellite, or UARS, will be the biggest NASA spacecraft to crash back to Earth, uncontrolled, since the post-Apollo 75-ton Skylab space station and the more than 10-ton Pegasus 2 satellite, both in 1979.
Russia's 135-ton Mir space station slammed through the atmosphere in 2001, but it was a controlled dive into the Pacific.
Some 26 pieces of the UARS satellite — representing 1,200 pounds of heavy metal — are expected to rain down somewhere. The biggest surviving chunk should be no more than 300 pounds (136 kilograms).
Earthlings can take comfort in the fact that no one has ever been hurt by falling space junk — to anyone's knowledge — and there has been no serious property damage. NASA put the chances that somebody somewhere on Earth would get hurt at 1-in-3,200. But any one person's odds of being struck were estimated at 1-in-22 trillion, given there are 7 billion people on the planet.
"Keep in mind that we have bits of debris re-entering the atmosphere every single day," Matney said in brief remarks broadcast on NASA TV.
In any case, finders definitely aren't keepers.
Any surviving wreckage belongs to NASA, and it is against the law to keep or sell even the smallest piece. There are no toxic chemicals on board, but sharp edges could be dangerous, so the space agency is warning the public to keep hands off and call police.
The $740 million UARS was launched in 1991 from space shuttle Discovery to study the atmosphere and the ozone layer. At the time, the rules weren't as firm for safe satellite disposal; now a spacecraft must be built to burn up upon re-entry or have a motor to propel it into a much higher, long-term orbit.
NASA shut UARS down in 2005 after lowering its orbit to hurry its end. A potential satellite-retrieval mission was ruled out following the 2003 shuttle Columbia disaster, and NASA did not want the satellite hanging around orbit posing a debris hazard.
Space junk is a growing problem in low-Earth orbit. More than 20,000 pieces of debris, at least 4 inches in diameter, are being tracked on a daily basis. These objects pose a serious threat to the International Space Station.
It’s coming but everyone is clueless about its destination. A defunct NASA science satellite is expected to fall back to Earth on Friday, showering debris somewhere on the planet although scientists cannot predict exactly where.
The 6.5-ton bus-sized Upper Atmosphere Research Satellite, or UARS, was carried into orbit during a space shuttle mission in 1991. It operated for 14 years, collecting measurements of ozone and other chemicals in the atmosphere.
Since completing its mission in 2005, UARS has been slowly losing altitude, tugged by Earth's gravity. On Friday, the 35-foot-long, 15-foot diameter (10.6-metres long, 4.5-metres diameter) satellite is expected to plunge into the atmosphere, NASA reported on its website.
On re-entry the satellite is expected to break into over 100 pieces out which 26 may survive the burn and crash onto earth’s surface.
The largest chunk may weigh around 136 kilograms. The satellite's orbit passes over most of the planet, from as far north as northern Canada to the southern part of South America.
However, the debris spread area would be around 805 kilometres, the location of which would be determined by the precise time at which the spacecraft will make the re-entry.
Assuaging fears about its impact on earth, NASA said the chance a piece of UARS debris will strike a person is about one in 3,200. The debris will mostly likely fall into an ocean or land in an uninhabited region of Earth.
Satellites as large as UARS re-enter Earth's atmosphere about once a year.
NASA said there have been no reports of any deaths or injuries to people from falling debris.
A team of Canadian scientists have discovered a "Trojan" asteroid that is caught in a synchronized orbit with the Earth. Many such asteroids have been found near other planets.
We get an explanation from Mike Brown,who is a planetary astronomer at the California Institute of Technology told, It's only been watched for a little bit of time right now and it's on the very intricate dance in front of the Earth. It's not between the Earth and the sun. It's actually in the same orbit as the Earth, so it goes around the sun in one year, just like the Earth goes around the sun in one year. And, on average, it's about the same distance from the sun as the Earth is.
It's close.on average, we overtake its position about every two months. So, in two months from now, we are going to be where it is right now.
The reason it takes so long to see, the reason it has been so long to find one of these things is because, most of the time when we're looking for asteroids or anything else in the solar system, we look out beyond the Earth. We look into the night sky. To find these things that are actually in the same orbit of the Earth, you really have to look in the very early morning or the very, very early evening, as the sky is really quite bright, so no one has found these things up until now.
It stays 60 degrees in front of the Earth as it goes. But it doesn't really stay in that spot. It goes ahead and then comes back behind and then keeps circling around.
And so it's in this position where it's a stable orbit, where it can stay in that place for a long time. But because of the Earth and because of the sun, it keeps on moving it around.
He told, I think they're interesting much more because of their scientific interest. They really are these windows into the very earliest solar system. They are materials that are left over from when the sun and the Earth and the planets formed. And they have been sitting around in space for that past 4.5 billion years.
And if we can find them and study them and figure out where they are and where they have come from, we have learned an awful lot about our very own origins.
This is actually a really good one to have found, because even though it has the same orbit as us, it can never come any closer to us than a certain distance, because it's stuck by the Earth, never or maybe in 20,000 years. We don't know what is going to happen then.
But, for the foreseeable future, it's going to be staying there. We are going to be watching it. It's going to be a really fun dance to watch.
