Click for next articleNASA just made an interstellar tweak to the Voyager 2 spacecraft, known as the "Big Bang", to keep its remaining 50-year-old science instruments running a little longer. But the supply of plutonium on each probe drops at about four watts a year on each spacecraft. Each spacecraft initially launched with 10 instruments, and Voyager 2 is now down to only three instruments . (Voyager 2 is at about 142 astronomical units or sun-Earth distances, while Voyager 1 is nearing 171 AU.) Each Voyager spacecraft first flew past Jupiter and Saturn, taking unprecedented imagery of the planets and their moons .