A quarter of a century ago this weekend, the Voyager spacecraft took one last, long look back before shutting down its camera for its interstellar mission. The 60 photographs from 6 billion kilometers away comprise our first solar system portrait.
This is our solar system from 6 billion kilometers away. Voyager 1 snapped this first-ever family portrait of our solar system on February 14, 1990 as its very last photograph before turning off its cameras. The final symbolic photograph was taken at the insistence of Carl Sagan, who iconically described the frame containing Earth as a Pale, Blue Dot.
The mosaic is composed of 60 frames, all at varying exposures and filters to pull out as much detail as possible of the planets in our solar system. The photo of the sun was set to the shortest possible exposure time (5/1000ths of a second) with the darkest filter designed for methane absorption, yet the extreme brightness still caused reflections in the camera's optics. Earth and Venus are both so tiny they don't even make a single pixel on the narrow-angle camera, with our home caught in the bright swath of an optical artifact. Mercury is lost in the sun's glare, and Mars hidden by a reflection artifact. Slightly larger, Uranus and Neptune are motion-blurred from Voyager's movement during the long exposure. Only Jupiter and Saturn are large enough to be clearly captured by our robotic photographer.
It was the final photograph taken by Voyager 1 before the spacecraft turned off its imaging system to conserve power and memory during its journey out of the system. The spacecraft was approximately 6 billion kilometers away from the Earth when it took the photograph, or 40.11 times the Earth-Sun distance, and 32° above the ecliptic plane. That's so far away, light from the sun took just over 5.5 hours to reach the spacecraft!
After taking the photographs, Voyager I shut down its cameras and continued on its long, slow, solitary journey into deep space.
Image credits: NASA