Goals: Pioneer 10 was the first spacecraft intended to fly by Jupiter, surviving the intense radiation that surrounds the giant planet and then on a trajectory that would take it out of the Solar System.
Accomplishments: The spacecraft became the first to fly beyond Mars' orbit, through the asteroid belt, and close to Jupiter, blazing a trail for the two Voyager spacecraft that were to follow and conduct more in-depth surveys. Long before and after flying by Jupiter, Pioneer 10 transmitted data on the magnetic fields, energetic particle radiation and dust populations in interplanetary space. As it passed through the Jupiter system, it transmitted hundreds of photos of the planet and its moons, along with measurements of the Jovian atmosphere.
Tracking Pioneer 10 and 11 as they sped away from the sun revealed what came to be called the "Pioneer Anomaly" - the spacecraft traveled about 5,000 km less than expected each year. In 2012, scientists announced the slight, but detectable effect of heat pushing back on the twin spacecraft explains unexpected slowing.