Pale Blue Dot is a photograph of planet Earth taken on February 14, 1990, by the Voyager 1 space probe from a record distance of about 3.7 billion miles, as part of the Family Portrait series of images of the Solar System.
In the photograph, Earth’s apparent size is less than a pixel; the planet appears as a tiny dot against the vastness of space, among bands of sunlight scattered by the camera’s optics.
Voyager 1, which had completed its primary mission and was leaving the Solar System, was commanded by NASA to turn its camera around and take one last photograph of Earth across a great expanse of space, at the request of astronomer and author Carl Sagan.
The design of the command sequence to be relayed to the spacecraft and the calculations for each photograph’s exposure time were developed by space scientists Candy Hansen of NASA’s Jet Propulsion Laboratory (JPL) and Carolyn Porco of the University of Arizona. After the planned imaging sequence was taken on February 14, 1990, the data from the camera was stored initially in an on-board tape recorder. Transmission to Earth was delayed also by the Magellan and Galileo missions being given priority over the use of the Deep Space Network. Then, between March and May 1990, Voyager 1 returned 60 frames back to Earth, with the radio signal travelling at the speed of light for nearly five and a half hours to cover the distance.
Three of the frames received showed the Earth as a tiny point of light in the empty space. Each frame had been taken using a different color filter: blue, green and violet, with exposure times of 0.72, 0.48 and 0.72 seconds respectively. The three frames were then recombined to produce the image that became Pale Blue Dot.
Of the 640,000 individual pixels that compose each frame, Earth takes up less than one (0.12 pixels, according to NASA). The light bands across the photograph are an artifact, the result of sunlight scattering off parts of the camera and its sunshade, due to the relative proximity between the Sun and the Earth. Voyager’s point of view was approximately 32° above the ecliptic. Detailed analysis suggested that the camera detected also the Moon, although it is too faint to be visible without special processing.