1950s-70s USA and Russia philatelic covers that are related to the early satellites development, manned and unmanned spaceflights to the moon.
1966-05-30 USA Surveyor 1
Launched on 30 May 1966, Surveyor 1 was the first spacecraft from the United States to perform a controlled landing on the surface of the moon. Once on the surface, Surveyor 1 took over 11,100 high-resolution, close-up photographs of the lunar landscape during three lunar day-night cycles (or about six earth weeks), where temperatures soared as high as 250 degree Farenheit (120 degree celcius) during the day and plunged to -260 degree Farenheit (-160 degree celcius). Particles as small as 1/50th of an inch (0.05 cm) in diameter could be detected.