A lethal radiation dose for a human is about 500 rads. Pioneer 10 flew through 200,000 rads of electron radiation at Jupiter in late 1973 and kept transmitting. This episode tells the 30 year biography of the first spacecraft to reach the outer solar system, from Gary Flandro’s planetary grand tour concept and James Van Allen’s push for a pathfinder, to the $380 million TRW contract and 25 million man hours that produced a spin stabilized probe with a nine foot dish, four plutonium-238 RTGs on long booms, and 11 scientific instruments.

Launched March 3, 1972 on an Atlas Centaur at over 32,100 miles per hour, Pioneer 10 became the first craft to cross the asteroid belt, proving it was mostly empty space rather than the sci-fi wall of debris. At Jupiter, radiation caused single event upsets that flipped bits in its computer and triggered false commands, which ground controllers corrected in real time. Its spinning imaging photopolarimeter built over 500 color images strip by strip, a broadcast that won an Emmy, and its instruments found an ionosphere on Io and proved Jupiter radiates more heat than it receives. We also cover the decades long Pioneer Anomaly, solved in 2012 as thermal recoil from the RTGs, the thermocouple degradation that ended the mission, and the last faint signal in January 2003.

• Why spin stabilization at 4.8 revolutions per minute kept the antenna locked on Earth without burning propellant
• How mounting the nuclear generators 10 feet from the chassis kept radiation from blinding the instruments
• What the asteroid belt crossing revealed about particle density, clearing the path for Voyager, Galileo, and Cassini
• How bit flipping radiation at Jupiter nearly crashed the probe and why planners accepted the risk of flying three Jupiter radii from the planet
• The Pioneer plaque mounted inward on the antenna struts, and the two million year journey toward Aldebaran