Nasa and the US Department of Defense are tracking the 35ft spacecraft, the Upper Atmosphere Research Satellite, or (UARS), as it heads towards the planet at five miles per second.
Mark Matney, an orbital debris scientist at NASA, said: “We know it is going to hit somewhere between 57 north latitude and 57 south latitude, which covers most of the inhabited world unfortunately.”
Experts say there is a one-in-3,200 risk of the space junk, which weighs six tons, hitting someone. However, its speed means that there will only be a 20-minute warning before it strikes.
Debris is expected to scatter across a 500-mile area, with the biggest chunk weighing 300lb, the weight of a large refrigerator.Â NASA has warned people not to touch the debris if they come across it because it is likely to have sharp edges.
The anticipated landing area spans cities as far north as Edinburgh and as far south as Cape Horn, on the southern coast of South America. NASA spokespeople have stressed that the risk to human life and property from UARS is small.
They cite the statistic that in 50 years of space exploration no one has ever been hurt by falling space junk, while they claimed that people were much more likely to be fatally struck by lightning.
The latest predictions of the satellites re-entry mean that the U.S. will miss out on the stunning sight of the spacecraft as it re-enters the atmosphere.
A Nasa spokesman said: “Re-entry is expected sometime during the afternoon 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 to 36 hours.”
The predictions came as astrophotographerÂ Thierry Legault in northern France captured video of the satellite. His clip shows the spacecraft appearing as a beaming mass of light as it plummets to Earth.Â To view astrophotographer Thierry Legault’s website, click here.
Mr Legault’s footage of UARS was captured through the lens of his Celestron EdgeHD 14in Schmidt-Cassegrain telescope in Dunkerque, France on September 15 – eight to nine days before its estimated re-entry. Filmed at an altitude of only 250km, the body of the UARS is visible, as are its solar arrays.
Mr Legault told the skywatching website Spaceweather.com: “The satellite appears to be tumbling, perhaps because a collision with satellite debris a few years ago. The variations in brightness are rapid and easily visible to the human eye.”
The biggest piece of space debris to fall from orbit was America’s 75-ton Skylab which hit Earth in 1979. UARS was launched in 1991 to measure the ozone layer, wind and temperature. It was officially decommissioned in 2005.
It is the biggest NASA spacecraft to “come back” in three decades, after Skylab fell in western Australia but Mr Matney said similar-sized pieces of spent rocket and satellite debris fall to Earth about once per year.
US Strategic Command’s Joint Space Operations Center is “keeping everyone – not just NASA but all the federal agencies that deal with public safety issues – informed about where it is and predictions of where it’s coming,” a spokeswoman said.
UARS now itâ€™s one of 370,000 pieces of junk floating in space at speeds of up to 22,000mph. The volume of debris was greatly increased by a 2007 Chinese anti-satellite weapon test and a 2009 crash-in-orbit of two satellites.
The widely criticised Chinese test used a missile to smash an ageing weather satellite into 150,000 pieces of 1cm debris and 3,118 pieces can be tracked by radar on the ground. The UARS is something of a relic – these days, Nasa satellites are designed to be light enough to burn up on re-entry, or to have fuel to fly up into a higher, longer-term orbit. [via The Telegraph (UK), Fox News and The Guardian (UK)]