For all of human history, one entire hemisphere of the Moon was a blank on the map. That ended in October 1959 when the Soviet probe Luna 3, a hermetically sealed cylindrical canister about 130 centimeters long, swung around the far side and photographed it using 35 millimeter isochrome film scavenged from downed American Genetrix espionage balloons. This episode unpacks the analog engineering that made it possible, from thermal control shutters to a fully automated zero gravity darkroom.

The mission nearly failed within hours of launch, when a weak radio signal and an internal temperature spike to 40 degrees Celsius threatened to melt the film emulsion. Ground controllers reoriented the spin axis and shut down equipment to save it. With no course correction rockets, Luna 3 relied on the first successful gravity assist in spaceflight, calcu ...