Scientists say there is a small chance debris from a satellite due to crash to Earth this weekend could land in Australia.
NASA's Upper Atmosphere Research Satellite (UARS), which weighs more than five tonnes, is expected to re-enter the Earth's atmosphere at 1058 AEST on Saturday.
The US-based Centre for Orbital and Re-entry Debris Studies estimates that re-entry could occur up to seven hours before or after this time.
The satellite's flight path includes several passes over Australia.
The Australian Space News website said the satellite poses a negligible threat to life and property on Earth.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"Most of the satellite will burn up on re-entry, with perhaps as many as 26 stronger or harder small pieces surviving to reach the surface," editor Jonathan Nally said in a statement.
"But with the majority of the Earth comprising oceans or uninhabited (or very sparsely populated) remote regions, the chances are overwhelming that any pieces of UARS that survive re-entry will fall harmlessly and never be seen again."
The UARS was launched in September 1991 and was decommissioned in December 2005.
After the satellite's productive days were over, NASA deliberately placed it into an orbit about 200 kilometres lower than its operational orbit.
"This was done to accelerate its eventual demise and means it is re-entering the atmosphere 20 years earlier than it would otherwise have done," explains Mr Nally.
"This was a very responsible thing to do. The longer a spacecraft stays in orbit, the more chance it has of being hit by other orbital debris, leading to a destructive breakup and therefore more bits of debris."
Debris from SkyLab, another satellite which plunged to Earth, was scattered over parts of Western Australia in 1979. Skylab weighed about 77 tonnes, many times more than the UARS.
Dr Alice Gorman of the Department of Archaeology at Flinders University in Adelaide said the re-entry of the UARS brings back memories of Skylab 32 years ago.
"There is the same exaggeration of the hazard through the media, public anxiety as the advance warning allows for speculation, and a lack of understanding of what the risks actually are," Dr Gorman said in a statement.
"Should it land in Australia, we might expect the same rush for souvenirs as we saw with Skylab, as anything that has been in space has a special meaning on Earth."
