The Tiangong space station is a space station in low Earth orbit (LEO). It is operated by the China Manned Space Agency (CMSA) as part of the China Manned Space Program. It is a space laboratory that hosts scientific experiments involving bioastronautics, microgravity physics, materials science and space technology. The station is permanently crewed, hosting a standard crew of three astronauts and six during handovers. Alongside the International Space Station (ISS), it is one of the only two currently operational space stations.