Last month marked the 40th anniversary of the historic Voyager 1 encounter with Jupiter in 1979. Voyager 1 was not the first robotic visitor to Jupiter; Pioneers 10 and 11 flew past the gas giant in 1973 and 1974. But while the Pioneers’ primitive spin-scan photopolarimeters took very good, groundbreaking images of the planet, they couldn’t compete with the TV cameras of the Voyagers.

The cameras, while not at the forefront of technology in the late-1970s, were still a reliable and proven method of capturing images in deep space. They had a pedigree stretching back to the early Mariner probes—not surprising, given that the Voyager program was essentially a continuation of Mariner (the two Voyager probes were developed under the moniker ‘Mariner-Jupiter-Saturn’).

Each Voyager carried a pair of TV cameras, mounted behind telescopes of differing focal length, giving the operators the option of taking images spanning 0.4 degrees (the NAC or narrow-angle camera), or 3 degrees (the WAC or wide-angle camera). In traditional photographic terms, both systems are squarely in the telephoto category.

Most of the valuable photographic data came from the NAC, given the greater resolution it offered. However, the overlooked WAC had two principal roles: to provide context views of the highly localized NAC shots, while also providing continuous photographic surveillance of global-scale features on Jupiter and its moons near the period around closest approach.

Voyager 1

Jupiter is huge. On 17 February 1979, Voyager 1 was no longer able to fit the planet into a single frame of the narrow-angle camera, even though the spacecraft was still a staggering 11 million miles away.

The wide-angle camera was similarly overwhelmed on 3 March 1979, when the planet was 1.4 million miles distant.