A six-tonne NASA satellite that is on course to crash back to Earth on Friday is not expected to hit North America, the US space agency said in its latest update.
"Re-entry is expected sometime during the afternoon of September 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period," NASA said in an update this afternoon.
"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."
All but 26 pieces of the Upper Atmosphere Research Satellite (UARS) are expected to burn up on re-entry into Earth's atmosphere.
The surviving chunks will include titanium fuel tanks, beryllium housing and stainless steel batteries and wheel rims.
NASA said the parts may weigh as little as 1kg or as much as 158kgs.
Orbital debris scientists say the pieces will fall somewhere between 57 north latitude and 57 south latitude, which covers most of the populated world. The debris footprint is expected to span 800kms.
The 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 in 1979.
Astronomy Ireland said earlier this week that the satellite will pass over Ireland from west to southeast.
It said: "If the satellite re-enters the atmosphere over Ireland, it is likely to deposit debris along a path from Galway/Limerick/North Clare to Waterford/Wexford.
"Regions further away from this strip are unlikely to be affected should UARS re-enter over the country."
Chairman of Astronomy Ireland David Moore said: "Any re-entry over Ireland will take place in the early hours of the morning, with the exact time changing each day.
"On entry, the satellite will disintegrate as a result of friction and light up spectacularly in the sky, not unlike a fireball or very bright meteor."
NASA has stressed that the risk to human life and property from UARS is small, adding that in 50 years of space exploration no one has ever been confirmed hurt by falling space debris.
There is a one in 3,200 chance that someone, somewhere in the world will be hit, according to NASA.
More frequent updates are scheduled for 12, six and two hours before it lands.
