China's Tiangong-1 spacecraft is expected to make its final plunge into the Earth's atmosphere within hours but the exact timing and location are still a mystery.
The European Space Agency expects the landing to happen early on Monday morning. South Korea's National Space Situational Awareness Organisation expects the station to re-enter the atmosphere between 2012 GMT on Sunday to 0412 GMT on Monday.
China has lost communication with the module so there is no way to control the downward flight. Experts are tracking the module as it orbits at an ever-decreasing altitude, however.
Based on the orbit, the space station should come back to Earth somewhere 43 degrees north and 43 degrees south, a range covering most of the US, China, Africa, southern Europe, Australia and South America. Russia, Canada and northern Europe are reportedly out of range.
The risk of Tiangong hitting the UAE or any other populated area is considered very low, however. The chances of any one person being hit by debris are considered less than one in a trillion because most of the anticipated re-entry zone is in the ocean and China has already said it is unlikely that large parts of the station will reach the ground.
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"Given Tiangong-1 has a larger mass and is more robust, as it is pressurised, than many other space objects that return uncontrolled to Earth from space, it is the subject of a number of radar tracking campaigns," said UK Space Agency's chief engineer Richard Crowther.
"The majority of the module can be expected to burn up during re-entry heating, with the greatest probability being that any surviving fragments will fall into the sea," he told BBC News.
The European Space Agency is leading the 13 space agencies following its path around the globe, hoping to forecast the most likely time and place for the laboratory's plunge.
The 10.4-metre-long (34.1-foot) Tiangong-1, or "Heavenly Palace 1" – a space module the size of a bus – was launched in 2011 to practise orbit experiments as part of China's space programme, which aims to place a permanent station in orbit by 2023.
The space lab was originally to be decommissioned in 2013 but its mission was extended. The last crew departed in 2013 and contact with it was cut in 2016.
China's chief space laboratory designer Zhu Zongpeng has denied Tiangong is out of control, but hasn't provided specifics on what, if anything, China is doing to guide the craft's re-entry.