NASA has squeezed at least another year of science out of Voyager 2 by cutting power to nonessential systems and switching to lower-power alternatives. Voyager 1 is expected to receive the same power-saving changes in the coming months. Space.com reports: Voyager 2 and its twin launched in 1977, called Voyager 1, rely on a form of nuclear battery known as a radioisotope thermoelectric generator that uses the heat produced by the decay of plutonium.