Thanks to orbital mechanics, a spacecraft heading to Jupiter must go most of the way there, then loop around the sun, zoom back close to Earth, and finally head out again on its mission to the largest planet in the solar system. That's the story of Juno, launched by NASA on Aug. 5, 2011, and due to arrive at Jupiter on July 4, 2016. Its journey required a boost in velocity, relative to the sun, which it received when it flew as close as 559 kilometers above Earth on Oct. 9, 2013.