Mission Type: Orbiter
Launch Vehicle: Thor-Able IV (no. 4 / Thor no. 219 / DM-1812-6A)
Launch Site: ETR / launch complex 17A
NASA Center: Goddard Space Flight Center
Spacecraft Mass: 43.2 kg
Spacecraft Instruments: 1) magnetometer; 2) ionization chamber; 3) Geiger-Mueller tube; 4) micrometeoroid momentum spectrometer; 5) photoelectric cell aspect indicator; 6) proportional counter telescope
Maximum Data Rate: 64 bits per second
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

Launched on a direct solar orbit trajectory, Pioneer 5 successfully reached heliocentric orbit between Earth and Venus to demonstrate deep space technologies and to provide the first map of the interplanetary magnetic field.

The spacecraft had originally been intended for a Venus flyby, but the mission was switched to a solar flyby. Pioneer 5 carried Telebit, the first digital telemetry system operationally used on a U.S. spacecraft; it was first tested on Explorer 6. The system used a 5-watt or a 150-watt transmitter, with a 5-watt transmitter acting as driver. Information rates varied from 64 to 8 to 1 bit per second.

Controllers maintained contact with Pioneer 5 until 26 June 1960, to a then record distance of 36.2 million kilometers from Earth (later surpassed by Mariner 2). The probe, using its 18.1-kilogram suite of scientific instruments, confirmed the existence of previously conjectured interplanetary magnetic fields.