After the first satellites were launched in 1957 and 1958 by the Soviet Union, the US began work on Project Mercury, with the aim of launching men into orbit. The USSR was secretly pursuing the Vostok program to accomplish the same thing, and launched the first human into space, the cosmonaut Yuri Gagarin, who, on 12 April 1961, was launched aboard Vostok 1 on a Vostok 3KA rocket and completed a single orbit. On 5 May 1961, the US launched its first astronaut, Alan Shepard, on a suborbital flight aboard "Freedom 7" on a Mercury-Redstone rocket. Unlike Gagarin, Shepard manually controlled his spacecraft's attitude. On 20 February 1962, John Glenn became the first American in orbit, aboard "Friendship 7" on a Mercury-Atlas rocket. The USSR launched five more cosmonauts in Vostok capsules, including the first woman in space, Valentina Tereshkova aboard Vostok 6, on 16 June 1963. Through 1963, the US launched a total of two astronauts in suborbital flights and four into orbit. The US also made two North American X-15 flights (90 and 91, piloted by Joseph A. Walker) that exceeded the Kármán line, the internationally recognized altitude used by the Fédération Aéronautique Internationale (FAI) to denote the edge of space.