1950s-70s USA and Russia philatelic covers that are related to the early satellites development, manned and unmanned spaceflights to the moon.
1967-09-08 USA Surveyor 5
Surveyor 5, launched on 8 September 1967, carried an alpha-ray scattering experimental package to conduct chemical tests on the soil composition.
Despite a serious helium leak that occurred during its trip to the Moon, Surveyor 5 touchdown successfully on 11 September 1967. Once on the ground, experiment work began to test analyzed the soil beneath it. The experiment indicated the existence of basalt and silicon. Surveyor 5 survived a lunar night and commenced operations again on October 15. The final transmission from the spacecraft was received on 17 December 1967.