1950s-70s USA and Russia philatelic covers that are related to the early satellites development, manned and unmanned spaceflights to the moon.
1973-01-08 USSR Luna 21/Lunokhod 2
Luna-21 entered Lunar orbit on January 12, 1973, and landed on January 15. The robotic rover, Lunokhod-2 rolled off the landing platform to explore the surface of the Moon for about 4 months. Like Lunokhod-1, it had two vidicon television cameras for navigational control, and four optical-mechanical cycloramic cameras. It returned 86 panoramas and over 80,000 navigational video pictures.