award for this presentation to the media. The motion of the spacecraft produced geometric distortions that later had to be corrected by computer processing. During the encounter, a total of more than 500 images were transmitted. The trajectory of the spacecraft took it along the magnetic equator of Jupiter, where the ion radiation was concentrated. Peak flux for this electron radiation is 10,000 times stronger than the maximum radiation around the Earth. Starting on December 3, the radiation around Jupiter caused false commands to be generated. Most of these were corrected by contingency commands, but an image of Io and a few close-ups of Jupiter were lost. Similar false commands would be generated on the way out from the planet. Nonetheless, Pioneer 10 did succeed in obtaining images of the moons Ganymede and Europa. The image of Ganymede showed low albedo features in the center and near the south pole, while the north pole appeared brighter. Europa was too far away to obtain a detailed image, although some albedo features were apparent. The trajectory of Pioneer 10 was chosen to take it behind Io, allowing the refractive effect of the moon's atmosphere on the radio transmissions to be measured. This demonstrated that the ionosphere of the moon was about above the surface of the day side, and the density ranged from 60,000 electrons per cubic centimeter on the dayside, down to 9,000 on the night face. An unexpected discovery was that Io was orbiting within a cloud of hydrogen that extended for about , with a width and height of . A smaller, cloud was believed to have been detected near Europa. It was not until after Pioneer 10 had cleared the asteroid belt that NASA selected a trajectory towards Jupiter that offered the slingshot effect that would send the spacecraft out of the Solar System. Pioneer 10 was the first spacecraft to attempt such a maneuver and became a proof of concept for the missions that would follow. Such an extended mission was not originally something that was planned, but was planned for prior to launch. At the closest approach, the velocity of the spacecraft reached , and it came within of the outer atmosphere of Jupiter. Close-up images of the Great Red Spot and the terminator were obtained. Communication with the spacecraft then ceased as it passed behind the planet. The radio occultation data allowed the temperature structure