??????????????????According to the announcement of China Manned Space Agency(CMSA),at 5 am, Apr.2,2018, Tiangong-1 stayed at an average altitude of about 138.8 km (perigee: 136.0 km; apogee: 141.6 km; inclination:42.70°). The estimated reentry time is at 8:49 am (the earliest time is at 8:11 am and the latest time is at 9:33 am ), 2 April, Beijing time. The reentry center is located at 19.4°W and 10.2°S.??????????????????