A Chinese space station called Tiangong-1 is set to fall to Earth this weekend.
The prototype satellite was launched in 2011, and several astronauts with China's Shenzhou missions visited the station over a two-year period.
Engineers lost their telecommunications link with the satellite in 2016, and it has since been orbiting uncontrolled.
It is now set to reenter the atmosphere - while much of the lab is set to burn up on reentry, debris is likely to reach the surface.
The odds of any debris hitting a populated area are low, and it is most likely to crash into the ocean.
Every week, on average, a substantial, inert satellite drops into our atmosphere and burns up. Monitoring these reentries and warning European civil authorities has become routine work for ESA’s #spacedebris experts #tiangong1 #reentry
Read more: https://t.co/5eBJzT2E67 pic.twitter.com/XI98duU1xV— ESA (@esa) March 30, 2018
While the reentry is likely to create a memorable light show for any astronomers lucky enough to spot it, it is currently challenging to predict when exactly the space station will fall.
Given the uncontrolled nature of Tiangong-1, experts will not be able to predict a precise point or time of reentry until shortly before it happens.
Map showing the area between 42.8 degrees North and 42.8 degrees South latitude (in green), over which Tiangong-1 could reenter. Graph at left shows population density. Credit: ESA CC BY-SA IGO 3.0
Holger Krag, head of ESA’s Space Debris Office, explained: "There will always be an uncertainty of a few hours in all predictions - even just days before the reentry, the uncertainty window can be very large.
"The high speeds of returning satellites mean they can travel thousands of kilometres during that time window, and that makes it very hard to predict a precise location of reentry."
Current forecasts put the reentry window from Saturday night to late Sunday evening, but the ESA warns this 'highly variable'.
Tiangong-1 - which is only a fraction of the size of the International Space Station - is considered a relatively large object to be falling to Earth, but around 50 larger objects have previously had uncontrolled reentries.
