Pioneer 2 was the last of the three project Able space probes designed to probe lunar and cislunar space. Shortly after launch at 07:30:00 UTC on 8 November 1958, the third stage of the launch vehicle separated but failed to ignite, and Pioneer 2 did not achieve its intended lunar orbit. The spacecraft attained a maximum altitude of 1550 km (963 miles) before reentering Earth's atmosphere at 28.7 N, 1.9 E over NW Africa. A small amount of data was obtained during the short flight, including evidence that the equatorial region around Earth has higher flux and higher energy radiation than previously considered and that the micrometeorite density is higher around Earth than in space.
The scientific instrument package had a mass of 15.6 kg (34.4 lb) and consisted of an STL image-scanning television system (which replaced the image scanning infrared television system on Pioneer 1), a proportional counter for radiation measurements, an ionization chamber to measure radiation in space, a diaphragm/microphone assembly to detect micrometeorites, a spin-coil magnetometer to measure magnetic fields to 5 microgauss, and temperature-variable resistors to record spacecraft internal conditions. The spacecraft was powered by nickel-cadmium batteries for ignition of the rockets, silver cell batteries for the television system, and mercury batteries for the remaining circuits. Radio transmission was at 108.06 MHz through a magnetic dipole antenna for the television system, telemetry, and doppler. Ground commands were received at 115 MHz. The spacecraft was to be spin stabilized at 1.8 rps, the spin direction approximately perpendicular to the geomagnetic meridian planes of the trajectory.