Its inevitable, what goes up must come down. On average there is one large piece of equipment that re-enters our atmosphere every week. Some are controlled and planned decommissioning of satellites after their useful life. They are purposely commanded for re-entry and burn-up in the atmosphere to avoid adding debris to our already crowded space orbits or worse, cause a collision with another satellite creating an enormous field of debris. Other objects that re-enter are left to fall on their own such as discarded rocket bodies and old satellite that ceased to operate long ago or malfunctioned and can no longer be controlled.
This coming March the 8,500kg (18,700lbs) Tiangong-1 Chinese space station is coming back to Earth. Launched in September 2011 and used for two manned missions, it suffered a malfunction and the Chinese have not been in control of it since 2016. The space station has been in a decaying orbit ever since, and now below the 300km altitude where Earth’s atmosphere is causing the space station to slow down due to aerodynamic drag it will soon make its re-entry.
Now there is no need to panic. Most of Earth is ocean, and we’ll probably not see anything let alone have a piece of it land in a city. However as this is a fairly large body, there is a good chance not all pieces will burn up and some may make it to the surface.
This isn’t the first time a space station makes a re-entry. The American Skylab at 77 tons re-entered in 1979, and Russian Mir (120 tons) made its re-entry in 2001.
For the Mir re-entry, Taco Bell even got it onto the re-entry buzz by anchoring a large
target off the Australian coast along the planned re-entry track, and should Mir crash into it there would be free tacos for all Americans. The fast food chain even took out an insurance policy just in case it would happen.
In early January 2018, Tiangong-1 is orbiting at an altitude of around 270-290km (to put that into perspective, ISS is at a 400km orbit) and in a 45 deg orbit, hence the re-entry will be within those latitudes. The green area in the map below is where Tiangong-1 could make a re-entry, and also marks where the re-entry could be observed.
It’s still too early to determine the time and location of potentially crash site, as Earth’s atmosphere is influenced by space weather and swells based on our Sun’s moods, which alters the drag force on the space station. However various space centers and organizations will continue to track the space station the coming weeks to improve the prediction.
You can follow everything at Aerospace.org for up to date information and predictions.
What could the re-entry look like? Below is a video shot by NASA of the Japanese Hayabusa spacecraft during a controlled re-entry on June 13, 2010