China is planning to conduct its first manual docking between a spacecraft and an orbiting space module Sunday.
Astronauts on the Shenzhou 9 spacecraft will try to dock with the Tiangong 1 lab module without using an automated system.
One of the three is China's first female astronaut, Liu Yang.
The Shenzhou 9 spacecraft was launched June 16 and it docked with the Tiangong 1 module two days later after a successful automatic procedure.
Officials say the attempt at the more challenging manual docking will serve in the construction of a larger space station, which China aims to complete by 2020.
The Tiangong 1 is an experimental module that will only stay in orbit until 2013 and will later be replaced.
Before China, the United states and the Soviet Union accomplished manual docking successfully in the 1960s.
The technique requires great accuracy as it involves two objects placed in the same orbit and revolving around Earth at thousands of kilometers per hour. The craft and the module need to connect very gently to avoid destroying each other.
After the rendezvous, two of the astronauts will move into the space station and perform scientific experiments before returning to Earth. The mission is expected to last 10 days.