Thirty-four years ago, NASA launched the Voyager 1 space probe as part of a Planetary Grand Tour proposed by scientists at the Jet Propulsion Laboratory. The plan was to use the technique of gravity assists to exploit an alignment of the outer planets that would allow for a single probe to visit Jupiter, Saturn, Uranus, Neptune, and Pluto using the encounter with each planet to slingshot it on a trajectory to the next.
The Grand Tour was eventually cut back, and Voyager 1 only visited Jupiter and Saturn before heading to the outer reaches of the Solar System and eventually interstellar space. The design life of the probe was approximately three to four years, just long enough to complete its primary mission, but once it became clear it would continue to function for some time to come, Carl Sagan proposed turning the spacecraft around to take a last look at Earth. His purpose was more philosophical than scientific; no one had ever seen Earth from such a great distance before. He was more interested in the perspective such an image might provide to a species that had, for the most part, never been away from home.
In the spring of 1990, Voyager 1 sent a series of images back to Earth, one of which we now know as the indelible portrait of our planet from over 3.5 billion miles away. In honor of Carl Sagan's birthday, I thought it appropriate to revisit this unique view of all that we know in this Universe, all that we call home, the only home we've ever known.