BEIJING - A manual docking will be conducted between Shenzhou IX?spacecraft and the orbiting Tiangong-1 lab module around noon Sunday, according to a spokesperson of China's manned space program.

Since Shenzhou IX?and Tiangong-1 successfully conducted an automatic docking and astronauts entered the Tiangong-1 module on June 18, both the spacecraft and the module have been operating normally and the three astronauts were in good condition, said the spokesperson.

All scientific tests have been conducted without any glitches and a manned conjoint flight has been realized, according to the spokesperson.

Compared with the automated docking, the upcoming manual docking will be more challenging in terms of orbit control, said Xie Jianfeng, a space scientist with the Beijing Aerospace Control Center.

Scientists have to get prepared to cope with changes in space environment, although space environment has been forecasted to be relatively calm around noon Sunday, he said.

According to Xie, changes in space environment had exerted "greater than expected" impact on orbit control of Shenzhou IX?on June 17, the second day after it lifted off from a launch center in Northwest China's Gobi Desert.

China's first unmanned space docking was completed successful last year with the docking of the Shenzhou?VIII?spacecraft and the Tiangong-1.