Pioneer 5

Image of spacecraft being assembled. — NASA's Pioneer 5 spacecraft before launch. Credit: NASA

What was Pioneer 5?

NASA's Pioneer 5 provided the first map of the interplanetary magnetic field. This mission was part of the famous Pioneer program—which included far-ranging Pioneers 10 and 11—that charted the space between the planets.

Pioneer 5 was the first deep space mission to carry Telebit, a digital telemetry system with data rates of 1 to 64 bits per second. Telebit was tested in Earth orbit by Explorer 6.
The spacecraft confirmed scientist's theories of a weak interplanetary magnetic field.
It was originally intended to go to Venus.

Nation	United States (7)
Objective(s)	Heliocentric Orbit
Spacecraft Mass	95 pounds (43.2 kilograms)
Spacecraft	P-2 / Able 6
Mission Design and Management	NASA / U.S. Air Force Ballistic Missile Division
Launch Vehicle	Thor Able IV (Thor Able IV no. 4 / Thor no. 219/DM-1812-6A)
Launch Date and Time	March 11, 1960 / 13:00:07 UT
Launch Site	Cape Canaveral / Launch Complex 17A
Scientific Instruments	1. Magnetometer 2. Ionization Chamber 3, Geiger-Mueller Tube 4. Micrometeoroid Momentum Spectrometer 5. Photoelectric Cell Aspect Indicator 6. Proportional Counter Telescope

Key Dates

Mar. 11, 1960: Launch

June 26, 1960: Last contact

In Depth: Pioneer 5

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.

Ready for Orbit — 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. Image Credit: NASA/JPL

The spacecraft had originally been intended for a Venus encounter, but the mission was switched to a direct entry into solar orbit.

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 1 to 64 bits per second.

Controllers maintained contact with Pioneer 5 until 11:31 UT on June 26, 1960, to a record distance of 22.6 million miles (36.4 million kilometers) from Earth (later beaten by Mariner 2).

The probe, using its 40-pound (18.1-kilogram) suite of scientific instruments, confirmed the existence of a previously conjectured weak interplanetary magnetic field. Information from the magnetometer was unfortunately unusable due to the instrument’s position within the spacecraft.

Pioneer 5 remains a derelict spacecraft circling the Sun.