The image data are starting to come in from NASA’s Juno spacecraft and if this is any indication, they’re going to be gorgeous!
On Monday, June 7, 2021 the Jupiter-orbiting spacecraft passed within just over 1000 kilometers of Ganymede. This is the closest any spacecraft has come to the Solar System’s largest moon since May of 2000, when NASA’s Galileo spacecraft was still cruising around the Jovian system.
See the full Junocam mosaic below:
Juno captured this image with its Junocam through a green spectral filter and what we see here is a monochrome result. Once the red and blue filtered raw data are aligned and calibrated we’ll start seeing some color versions.
According to NASA in a news release:
This image is a preliminary product – Ganymede as seen through JunoCam’s green filter. Juno is a spin-stabilized spacecraft (with a rotation rate of 2 rpm), and the JunoCam imager has a fixed field of view. To obtain Ganymede images as Juno rotated, the camera acquired a strip at a time as the target passed through its field of view. These image strips were captured separately through the red, green, and blue filters. To generate the final image product, the strips must be stitched together and colors aligned.
In the meantime, here’s a look at Ganymede in approximate natural color as seen by Galileo (and processed by me):
Ganymede is not only Jupiter’s largest moon but also the largest moon in the entire Solar System. At 3,273 miles (5,268 km) across it’s even larger than Mercury and Pluto, and about 3/4 the size of Mars. Ganymede is the only moon found to generate its own magnetosphere, the result of a liquid iron core, which is even strong enough to hold its own within Jupiter’s powerful and far-reaching magnetic field.
Update 6/9/21: Here’s my first processing of the Junocam RGB spectral filter data (using preview PNGs) captured on June 7, adjusted to approximate natural coloration on the moon based on USGS color mosaics and rotated ~90º ccw to fill the frame. North on Ganymede is to the left in this view: