Tiangong, officially the Tiangong space station, is a permanently crewed space station constructed by China and operated by China Manned Space Agency in low Earth orbit between 340 and 450 km above the surface. It is China's first long-term space station, part of the Tiangong program and the core of the "Third Step" of the China Manned Space Program; it has a pressurised volume of 340 m³, slightly over one third the size of the International Space Station.