Tiangong, officially the Tiangong space station, is a permanently crewed space station constructed by China and operated by China Manned Space Agency. Tiangong is a modular design, with modules docked together while 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. The space station aims to provide opportunities for space-based experiments and a platform for building capacity for scientific and technological innovation.