Spacecraft operators usually plan for decommissioned space stations to re-enter the atmosphere over a remote location in the ocean. That ensures falling debris not burned away during re-entry won’t cause any harm or significant damage on impact.
Xinhua reported that China will continue to monitor Tiangong-1, “strengthen early warning for possible collision with objects” and, if necessary, release internationally a forecast of where it will be falling. This indicates some level of uncertainty about where the space lab will fall, as The Washington Post points out.
Jonathan McDowell, an astrophysicist with the Harvard-Smithsonian Center for Astrophysics, told the Guardian that the announcement suggested that the station was out of China’s control.
“You can’t really steer these things,” McDowell told the newspaper. “Even a couple of days before it reenters we probably won’t know better than six or seven hours, plus or minus, when it’s going to come down. Not knowing when it’s going to come down translates as not knowing where it’s going to come down.”
Although most of the space station will burn as it reenters the atmosphere, some denser parts would still crash on Earth, McDowell said.
“There will be lumps of about [220 pounds] or so, still enough to give you a nasty wallop if it hit you,” he said, adding that the debris probably wouldn’t cause widespread damage.
Article source: http://www.huffingtonpost.com/2016/09/22/chinese-space-station-crash-on-earth-2017_n_12150118.html?utm_hp_ref=hawaii&ir=Hawaii