The space program of the People's Republic of China is directed by the China National Space Administration (CNSA). Its technological roots can be traced back to the late 1950s, when the People's Republic began a ballistic missile program in response to perceived American (and, later, Soviet) threats. However, the first Chinese crewed space program only began several decades later, when an accelerated program of technological development culminated in Yang Liwei's successful 2003 flight aboard Shenzhou 5. This achievement made China the third country to independently send humans into space.