Carl Sagan's Pale Blue Dot
Long ago on February 14, 1990, the Voyager 1 turned what was then a state-of-the-art camera toward Earth, which appeared as a "pale blue dot," as described by the late astronomer Carl Sagan:
"Look again at that dot. That's here," wrote Sagan in his 1994 book, titled Pale Blue Dot: A Vision of the Human Future in Space. "That's home. That's us."
Cosmic remix of Voyager 1
Scientists at NASA's Jet Propulsion Laboratory decided to revisit the old photo, in celebration of the 30th anniversary of this timeless photo. They used new image-processing tools and techniques, and focused on "respecting the intent of those who planned the image," according to a NASA press release. The photo looks sharper, with a crisp-and-clean feeling that feels somehow brighter for its age.
The full version of the remixed image is also available.
Voyager 1 took this photo of Earth after the primary exploration phase of its mission was complete. Launched in 1977, the intrepid probe made flybys of Jupiter and Saturn, and amassed close-up photos of the gas giants that went unrivaled for decades.
At the time of the photo, in February 1990, Voyager was 6 billion kilometers (3.7 billion miles) from the Earth, which is 40 times the average distance from the Earth to the Sun. The probe was farther out than Neptune, and located roughly 32 degrees above the ecliptic plane of our solar system. When the photo was taken, Voyager 1 was so far from Earth that the blue light in the image of the planet had taken 5 hours and 36 minutes to reach it.
Voyager 1's camera, and eventual death
In effect, every time we return to the "Pale Blue Dot" image, we're echoing the action of Voyager, looking back in time at us.
Voyager 1's camera used three color filters: violet, blue, and green. Conjoined, the spectral filters created a false-color image, which made Earth appear as a light-blue dot, less than one pixel wide. This single-pixel planet seemed to float, arrested in space by an intersecting ray of dramatic, scattered, sunlight — created by Voyager's camera.
"The planet occupies less than a single pixel in the image and thus is not fully resolved," said NASA.
The remixed Pale Blue Dot is brighter than the original, and artifical effects caused by the extreme magnification of Voyager 1's camera were removed.
"The brightness of each color channel was balanced relative to the others, which is likely why the scene appears brighter but less grainy than the original," said NASA in a press release. "In addition, the color was balanced so that the main sunbeam appears white, like the white light of the Sun."
The Pale Blue Dot was intended as a final farewell to the Voyager 1 mission, and its camera subsequently shut down 34 minutes after it was taken, to conserve energy.
This is why, despite the dangers of radiation and wear, both Voyager 1 and Voyager 2 are still running, in a final coda of their sister-missions.