Goals: Voyager 1 and 2 were designed to take advantage of a rare planetary alignment to explore the outer solar system. Voyager 1 targeted Jupiter and Saturn before continuing on to chart the far edges of our solar system.

Accomplishments: Voyager 1 has been observing the interplanetary medium throughout its journey, and is now exploring the outermost reaches of where the solar wind and the sun's magnetic field dominate space. In December 2004, the spacecraft crossed the termination shock (where the speed of the solar wind drops below the speed of sound) at 94 AU (about 14 billion km from the sun, more than twice the distance to Pluto). Since then, Voyager 1 has been operating in the heliosheath environment, a region about 40 to 50 AU (3.7 billion to 4.7 billion km) thick where the solar wind mixes with the interstellar wind.