Voyager 1 Still Transmitting Data

It is a remarkable testament to 1970s engineering that a spacecraft built with less computing power than a modern car key fob is now humanity's most distant envoy. To catch the faint whisper from this probe across the void, NASA employs the massive, continent-spanning antennas of its Deep Space Network (Review), which must listen with incredible sensitivity. The signal they are trying to hear has traveled for so long that it is billions of times weaker than the power of a watch battery by the time it arrives. A simple command sent from Earth and its corresponding confirmation would take nearly two full days to complete this interplanetary conversation.

Originally designed for a "Grand Tour" of the outer planets, Voyager 1 completed its primary mission of studying Jupiter and Saturn by 1980. Its journey, however, was just beginning. In 2012, it made history by crossing the heliopause, the protective bubble of particles and magnetic fields generated by our Sun, officially entering the space between stars. Today, its instruments continue to measure the conditions in this uncharted territory, sampling cosmic rays and magnetic fields that have traveled the galaxy for millions of years. It is our first, and so far only, active probe sending back priceless postcards from the cosmic shore.