1950s-70s USA and Russia philatelic covers that are related to the early satellites development, manned and unmanned spaceflights to the moon.
1962-04-23 USA Ranger 4
After a successful launch on 23 April 1962, communication with Ranger 4 failed. The spacecraft could be tracked, until it crashed on the far side of the Moon on 26 April 1962, but were unable to collect any data. Ranger 4 was the first object from the United States to reach the moon.