A Cassini map of Jupiter
In 2018 I created a map combining Cassini's nearly global coverage of Jupiter with Juno's superior polar imagery. This combined map (14400x7200 pixels) is hosted at the Planetary Society (TPS) website and can be found on this page.
The combined map was created by adding Juno polar imagery to a Cassini-only map of Jupiter that I had created earlier. Since in a way the combined map really is partially fictional (as explained on the TPS page mentioned above), the Cassini-only map can be found below together with a description of how it was made.
The Cassini-only map of Jupiter below was created from roughly 100 images obtained by the Cassini spacecraft at the end of December 2000 from a distance of a little under 10 million km. These images have a resolution of roughly 65 km/pixel so to match this the original map has a size of 7560x3780 pixels (21 pixels per degree) but the version here is 3600x1800 pixels.
Cassini's closest approach to Jupiter occurred at the end of December 2000. At that time Cassini acquired complete global coverage of Jupiter by taking a series of 3x2 mosaics using two color filters, blue (BL1) and a near-infrared filter (CB2). For creating the map I used images covering an entire Jovian rotation (about 10 hours) plus some extra images for suitable overlap. There were no gaps in this coverage except for small regions near the poles and a few very small spots closer to the equator.
For creating the map I needed synthetic green images. I created these by determining which combination of CB2 and blue yielded the best synthetic green images in a least squares sense, using green images obtained from a greater distance as a guide. Similarly, I created synthetic red (or more specifically, CB1) images from the CB2 and blue images. This was necessary because if the CB2 images are used as red the color balance becomes less realistic. In particular, it is impossible to achieve accurate color by making the brightest zones whitish without making darker belts too reddish.
I then created the map by creating full color maps from each CB2/blue image pair. To create these maps I first had to process the raw spacecraft images by radiometrically correcting them. I then processed the resulting images in Photoshop to remove any remaining artifacts (these were usually minor). The next step was to reproject the images to simple cylindrical projection, correcting for the different illumination and atmospheric scattering across the field of view on the fly. I then created the synthetic red and green maps, made a full color map from these and adjusted the color balance.
Following this I had about 50 full color maps. I then mosaicked these together into a global full color map, using Photoshop to remove seams and the effects of different illumination that weren't fully corrected for during the previous processing steps. I finally fixed the poles by reprojecting the polar regions to polar projection, making some minor adjustments to the north polar region and adding some cloned and/or fictional data to the south polar region near the pole. I then reprojected the fixed poles back to cylindrical projection.
An experimental rendering I made using this map can be seen on the experimental renderings page.
Click the map below to download the full size map (2.1 MB 3600x1800 pixel JPG).
The map is in simple cylindrical projection with latitudes running with a uniform interval from -90 (bottom) to 90 (top). Longitude 0 (System III) is at the left edge of the map. Latitudes are planetographic. The map should be rendered by projecting it onto an ellipsoid with an equatorial radius of 71516 km and a polar radius of 66871 km or some equivalent units. See also my planetery rendering tips page for further info.
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