Mission Type: Orbiter
Launch Vehicle: Thor-Able I (no. 2 / Thor no. 129 / DM-1812-6)
Launch Site: Cape Canaveral, United States, launch complex 17A
Spacecraft Mass: 39.6 kg
Spacecraft Instruments: 1) ionization chamber; 2) magnetometer; 3) temperature sensor; 4) micrometeoroid sensor; 5) proportional counter and 6) imaging system
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center, http://nssdc.gsfc.nasa.gov/

For this third Air Force launch of a lunar orbiter, engineers introduced a number of changes to the Thor-Able launcher.

The probe included a new TV scanner and a new type of battery, as well as a new cosmic-ray telescope to study the Cherenkov Effect.

Pioneer 2, like its predecessors, never reached its target. A signal from the ground shut down the Thor launch vehicles stage 2 earlier than planned. Additionally, when the X-248 third stage engine separated, it failed to fire. As a result, the probe burned up in Earths atmosphere only 45 minutes after launch.

During its brief mission, it reached an altitude of 1,550 kilometers and sent back data that suggested that Earths equatorial region had higher flux and energy levels than previously thought. The information also indicated that micrometeoroid density was higher near Earth than in space.

Investigators concluded that the third-stage engine had failed to fire because of a broken wire.