The duo are to face in-orbit challenges, such as the real state of weightlessness

The Shenzhou XI manned spacecraft was scheduled to dock with the Tiangong II space lab in the early hours of Wednesday morning as astronauts start their busy, monthlong schedule, the space authority said.

After nearly two days of spaceflight, the Shenzhou XI will conduct a computer-controlled docking with the space lab. Then the two astronauts - 49-year-old Jing Haipeng and 37-year-old Chen Dong - will enter the lab and start the longest space stay by Chinese astronauts, according to the China Manned Space Agency.