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Pioneer 2

Pioneer 2 was the last of the three project Able space probes[?] designed to probe lunar and cislunar[?] space. Shortly after launch, 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.

Spacecraft design

Pioneer II was nearly identical to Pioneer 1. It consisted of a thin cylindrical midsection with a squat truncated cone frustrum on each side. The cylinder was 74 cm in diameter and the height from the top of one cone to the top of the opposite cone was 76 cm. Along the axis of the spacecraft and protruding from the end of the lower cone was an 11 kg solid propellant injection rocket and rocket case, which formed the main structural member of the spacecraft. Eight small low-thrust solid propellant velocity adjustment rockets were mounted on the end of the upper cone in a ring assembly which could be jettisoned after use. A magnetic dipole antenna also protruded from the top of the upper cone. The shell was composed of laminated plastic. The total mass of the spacecraft after vernier separation but before injection rocket firing was 39.5 kg.

The scientific instrument package had a mass of 15.6 kg and consisted of an STL image-scanning television system (which replaced the image scanning infrared television system on Pioneer I), 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.

NASA photo of the Pioneer 2 probe.

See also: Pioneer program

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