Pioneer 5 was the first spacecraft to carry a digital telemetry system into interplanetary space.
It was also the first to observe the interplanetary magnetic field.
It was the only success of the seven interplanetary missions launched by the U.S. and Soviet Union in 1960.
This spacecraft was initially intended to be sent to Venus, but the mission was changed to test new technologies.
Pioneer 5 carried Telebit, the first digital telemetry system (orginally tested on Explorer 6).