China plans to expand its space station to six modules from three in coming years, offering astronauts from other nations an alternative platform for near-Earth missions as the NASA-led International Space Station (ISS) nears the end of its lifespan.

The operational lifetime of the Chinese space station will be more than 15 years, the China Academy of Space Technology (CAST), a unit of China’s main space contractor, said at the 74th International Astronautical Congress in Baku, Azerbaijan, on Wednesday.

That would be more than the 10 years previously announced.

China’s self-built space station, also known as Tiangong, or Celestial Palace in Chinese, has been fully operational since late 2022, hosting a maximum of three astronauts at an orbital altitude of up to 450 km (280 miles).

At 180 metric tons after its expansion to six modules, Tiangong is still just 40% of the mass of the ISS, which can hold a crew of seven astronauts. But the ISS, in orbit for more than two decades, is expected to be decommissioned after 2030, about the same time China has said it expects to become “a major space power”.