Some readers will remember the farewell family portrait of the solar system snapped by Voyager I on Valentine’s Day, 1990. They may also recall astronomer Carl Sagan’s comment that our home planet, seen from space, appears as a “pale blue dot.” These pictures were the last taken by the spacecraft’s cameras before they were shut off in order to repurpose the computer that controlled them.
Voyager 1 and its twin Voyager 2 were launched by NASA in 1977 to fly by the planets of the outer solar system and to capture close-up images of the gas giants Jupiter, Saturn, Uranus and Neptune. Having fulfilled this mission and more, and now at a distance of 130 AU (astronomical units) or 19.5 billion kilometers from the sun, Voyager I has travelled farther from the earth and sun than any other human artifact. The Voyagers’ discoveries about the giant planets have provided enough material to rewrite astronomy textbooks. The Voyager mission was originally intended to last for five years, but has been extended as the instruments continue to function and can be reprogrammed remotely.
In 2012, Voyager 1 crossed into interstellar space, beyond the heliosphere, which marks the limits of the sun’s magnetic field and solar wind. The Voyager Interstellar Mission (VIM) extends the spacecraft’s mission, from studying the outer planets to interstellar space. It can now observe the behavior of particles and waves without the influence of the solar wind. Both spacecrafts send back information collected by magnetometers, infrared, ultraviolet, cosmic-ray and charged-particle sensors and plasma detectors to the Deep Space Network (DSN) based at the Jet Propulsion Lab at Caltech.
Among other things, Voyager I sends back recordings of the sounds of deep space. You can listen here. “Pale Blue Dot” became the title of Sagan’s 1994 book, in which he wrote: “That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”