1950s-70s USA and Russia philatelic covers that are related to the early satellites development, manned and unmanned spaceflights to the moon.
1966-04-01 USSR Luna 10
On 3 April 1966, the Soviet Union Luna 10 became the first to successfully orbit the moon. Launched on 31 March 1966 and arrived moon on 2 April 1966, Luna 10 became the first spacecraft to successfully go into orbit around another celestial body. While in orbit, Luna 10 studied radiation levels, cosmic ray intensities, and took readings of the moon's weak magnetic field. The spacecraft successfully transmitted data for two months, circling the moon 460 times before its mission came to an end on May 30, 1966.