It’s been decades… Juno images of Ganymede

On 7 June 2021 Juno came within ~1000 km of Ganymede’s surface. Jupiter’s moon Ganymede was imaged by Voyager in 1979, and by Galileo from 1996 to 2000. Now the evolution of Juno’s elliptical polar orbit has brought it in to where Juno’s orbit crosses the plane of the moons' orbits, bringing the spacecraft close enough to get the best images of Ganymede seen in decades. Approaching from the darkside the Juno Stellar Reference Unit acquired one image illuminated by Jupiter-shine, and then JunoCam snapped 4 images of the terminator and illuminated hemisphere as the spacecraft flew by. The geometry was such that the JunoCam images covered territory first imaged by Voyager at ~1 km/pix. Although the resolution was similar, the JunoCam image quality is better, especially since a number of the Voyager images were smeared. Juno’s images will likely eventually replace Voyager images in the USGS map. These beautiful close-up images lead to emerging new understanding of Ganymede’s history.