Nearly 50 years after leaving Earth, NASA's Voyager 1 is approaching an extraordinary milestone that will highlight just how far humanity's most distant spacecraft has traveled. But keeping the aging explorer operational has become an increasingly difficult challenge as its power supply slowly fades.

NASA engineers recently achieved two important developments in their effort to extend the mission. In September, they completed a complex energy conservation project designed to preserve the spacecraft's remaining scientific capabilities. Then, on October 20, Voyager 1 unexpectedly resumed communication with Earth after a mysterious 48-hour interruption.

NASA Engineers Find a Clever Way to Save Power

In early September, the Voyager team successfully replaced three devices aboard Voyager 1 with alternatives that consume less electricity.…