China's Tiangong space station is scheduled to be completed before the end of this year and will become a massive spacecraft stack with a combined weight of nearly 100 metric tons, according to a program leader.

Zhou Jianping, chief designer of the nation's manned space program, said the assembly phase of the Tiangong program will begin in May and will involve the launch of two astronaut crews, two space labs and two cargo ships.

Zhou made the remarks on Friday afternoon at the Great Hall of the People in Beijing before the opening of the fifth session of the 13th National Committee of the Chinese People's Political Consultative Conference.

The scientist is a member of the CPPCC National Committee, the top political advisory body in China.

"We will send six astronauts in the Shenzhou XIV and XV mission crews. The Shenzhou XIV crew will be responsible for monitoring the docking between the Tianhe core module and the two space labs and then configuring the two labs," he said.

"The Shenzhou XV crew will fly to the station around year's end to meet their Shenzhou XIV peers and that will be an exciting moment that all of us are eager to see."

Upon Tiangong's completion, it will consist of three major components－a core module linked with two large space labs, two Shenzhou spacecraft and one cargo ship, weighing around 100 tons.

A total of six astronauts will stay inside the station, the largest space-based infrastructure China has ever built, for a certain period of time before the Shenzhou XIV crew return to Earth, according to Zhou.

He said the Tiangong station will be a platform for scientific experiments and technology demonstrations in a wide range of research fields like biology, materials science and micro-gravity hydrodynamics.

China launched the first, and central, component of its Tiangong station－the Tianhe core module－in April and sent the Shenzhou XII crew to stay inside it from mid-June to mid-September.

The 22.5-ton, three-section module is now occupied by the Shenzhou XIII crew－Major General Zhai Zhigang, Senior Colonel Wang Yaping and Senior Colonel Ye Guangfu－who arrived at the station in mid-October and are scheduled to stay there for six months.

In their first spacewalk in November, Wang became China's first female spacewalker.

She performed extravehicular operations that lasted six and a half hours together with mission commander Zhai.

"The Shenzhou XIII crew have traveled in space for 140 days. They are doing well and have fulfilled all of the tasks we gave them. They will return to Earth in mid-April," Zhou said.