deorbited in 2013, [10]  and replaced over the following decade by the larger  Tiangong-2 and  Tiangong-3  modules. Tiangong-1 is expected to be visited by three  Shenzhou  missions during its two-year operational lifetime. The first of these, the unmanned Shenzhou 8 , successfully docked with the module in November 2011, [11] [12]