On September 29, 2011, China launched its first experimental space station called Tiangong-1 (“Heavenly Palace”). During its operational lifetime of two years, the space station was visited by three Shenzhou spacecraft, demonstrating three successful dockings, first two unmanned missions in November 2011 (Shenzhou 8) and June 2012 (Shenzhou 9), followed by one manned mission in June 2013 (Shenzhou 10).
The space station is of cylindrical shape with a length of 10.4 m and an overall diameter of up to 3.4 m. There are two solar panels attached with a total cross-section of approximately 35 m². The station consists of two sections: a service module (for power generation, attitude/orbit control, telecommunications, etc.), and a pressurized habitat equipped with the docking system. The total mass of the space station is in the order of 8.5 metric tons.
The original plans were to deorbit Tiangong-1 in 2013, leading to a controlled re-entry over uninhabited areas of the Earth in order to avoid an undue risk to people on the ground caused by surviving fragments. Instead, the orbit of Tiangong-1 was regularly raised during the last three years. The last re-orbit maneuver was executed in December 2015.
On March 23, 2016, the Manned Space Engineering Office of China announced that Tiangong-1 had ceased operations. This will potentially lead to an uncontrolled re-entry in the second half of 2017, if no controlled re-entry maneuver is performed until about mid of 2017.
The size, mass, and materials of Tiangong-1 make a complete demise during re-entry impossible. Up to 40% of dry mass is expected to survive (>3 metric tons). The casualty risk is currently estimated to be in the order of 1:1,000, which is ten times higher than the risk limit considered as acceptable on international level.