BEIJING (AP) — Three Chinese astronauts docked to their country’s space station early Wednesday, where they will overlap for several days with the three-member crew already on board and expand the facility to its maximum size.

The docking with Tiangong Station occurred at 5:42 a.m. Wednesday (4:42 p.m. Tuesday ET), about six and a half hours after the Shenzhou-15 spacecraft lifted off on a Long March carrier rocket. -2F from the Jiuquan Satellite Launch Center on Tuesday night.

The six-month mission, commanded by Fei Junlong and crewed by Deng Qingming and Zhang Lu, will be the last in the station’s construction phase, according to the China Manned Space Agency. The third and final station module docked with the station a month ago, one of the latest steps in China’s effort to maintain a constant manned presence in orbit.

An image of the Shenzhou-15 and Shenzhou-14 crews in space on Wednesday.Guo Zhongzhen/Xinhua via AP

The Shenzhou-15 crew will spend several days working with the existing 3-member Tiangong crew, who will then return to Earth after their six-month mission.

Fei, 57, is a veteran of the four-day Shenzhou-6 mission in 2005, the second time China sent a human into space. Deng and Zhang are making their first space flights.

The station has now been expanded to its full size, with three modules and three attached spacecraft for a total mass of almost 100 tons.

Tiangong can accommodate six astronauts at a time, and the handover will take about a week. That marks the first rotation of the station’s orbiting crew.

China has not yet said what additional work is needed to complete the station. Next year it plans to launch the Xuntian Space Telescope which, although not part of Tiangong, will orbit in sequence with the station and may occasionally dock with it for maintenance.

Without the spacecraft attached, the Chinese station weighs about 66 tons, a fraction of the International Space Station, which launched its first module in 1998 and weighs about 465 tons.

With a lifespan of 10 to 15 years, Tiangong could one day be the only space station still in operation if the International Space Station is retired in the next few years as planned.

While China’s manned space program is officially three decades old this year, it really got its start in 2003, when China became the third country after the US and Russia to send a human into space using its own resources.

The program is run by the ruling Communist Party’s military wing, the People’s Liberation Army, and has been carried out almost entirely without outside support. The United States barred China from the International Space Station because of its program’s military ties, though China has engaged in limited cooperation with other nations’ space agencies.

China has also had successes in unmanned missions: its Yutu 2 rover was the first to explore the little-known far side of the moon.

China’s Chang’e 5 probe also returned lunar rocks to Earth in December 2020 for the first time since the 1970s, and another Chinese rover is searching for evidence of life on Mars.

Officials are reportedly considering an eventual crewed mission to the moon, though no timetable has been offered, even as NASA presses ahead with its Artemis lunar exploration program that aims to send four astronauts around the moon in 2024. and land humans there in 2025.

While for the most part it went smoothly, China’s space program also generated controversy. Beijing has played down complaints that it has allowed rocket stages to fall unchecked to Earth after NASA accused it of «failing to meet responsible standards regarding its space debris.» In that case, parts of a Chinese rocket landed in the Indian Ocean.

China is also reportedly developing a top-secret space plane and its growing space capabilities are included in the latest Pentagon defense strategy, which said the program was a component of China’s «holistic approach to joint warfare.»