1950s-70s USA and Russia philatelic covers that are related to the early satellites development, manned and unmanned spaceflights to the moon.
1959-03-03 USA Pioneer 4
The United States followed Luna 1 in March 1959 with its Pioneer 4 fly-by spacecraft. Launched on 3 March 1959, Pioneer 4 passed within 60,000 kilometers (37,300 miles) of the moon, returned data on lunar radiation levels, then entered a solar orbit.
Photo: Flight path of Pioneer 4, the sun satellite.