Processed Cassini PDS images, Fun with the PDS files Options

[Bjorn Jonsson]

While using the Cassini PDS images to make a big cylindrical map of Saturn's southern hemisphere I decided to also process a few PDS images to make some mosaics and color composites as 'by-products'.

In September and October 2004 Cassini continuously observed Saturn for several weeks using eight different filters (CB1, MT1, CB2, MT2, CB3, MT3, BL1 and UV3). The result was a 2x2 image atmospheric movie and (needless to say) lots of interesting images. The images in this and the following posts are derived from a few of these images.

Unless otherwise noted all of the images I used for the color composites I'm posting here are from this sequence of images and were obtained from a distance of 7.2 million km on September 30, 2004.

Here is a 2x2 mosaic of the southern hemisphere:



The overall color is fairly accurate (possibly a bit too saturated), however, small scale features have been sharpened slightly. This image is composed from CB1, BL1 and synthetic green images based on the CB1 and BL1 images. Provided the synthetic green image is properly made the end result is almost indistinguishable from color composites where GRN images are available.

[Bjorn Jonsson]

About 25 years ago the Voyager spacecraft obtained well known false color images of Saturn. This one is a good example. These images were composed by using green, violet and ultraviolet images as red, green and blue, respectively.

As far as I know something similar based on Cassini images has not been publicly released. The image below is composed by using CB3, BL1 and UV3 as red, green and blue, respectively:



The images used for making this false color image were obtained from a distance of 26 million km on May 12, 2004.

This is a version where the color saturation has been increased and small scale details sharpened with an unsharp mask:



Some color fringing is visible, especially near some of the spots. This is due to Saturn's rotation, the three images where obtained over a period of several minutes.

[helvick]

As far as I know something similar based on Cassini images has not been publicly released. The image below is composed by using CB3, BL1 and UV3 as red, green and blue, respectively:

I really like the first version - absolutely beautiful.

[Bjorn Jonsson]

Like the preceding images, the image below is composed from CB3, BL1 and UV3 images. However, the resolution is much higher:



Color saturation has been increased and small scale details sharpened using an unsharp mask. The limb is somewhat bluish due to Rayleigh scattering. Interestingly, many of the spots (storms) also appear bluish, as well as a large area around the south pole. In addition, lots of small scale details are visible in Saturn's atmosphere.

To compensate for Saturn's rotation between the different images the images were projected onto a seamless, cylindrical map that was then rendered from the spacecraft's vantage point.

This also made it possible to check what Saturn's south pole would look like from directly 'below':



As before, color saturation has been increased and small scale details sharpened using an unsharp mask.

That's it for now. I may post more images later. There are thousands (or tens of thousands) of spectacular PDS images just waiting to be processed .

[dilo]

Thanks, Bjorn. Really spectacular images!

[djellison]

NOW we're talking


Doug

[Bjorn Jonsson]

Now I have almost finished the map of Saturn's southern hemisphere mentioned in the first message of this thread. Its resolution is 25 pixels/degree. I used 56 images (28 CB1 and 28 BL1 images plus synthetic green) to get something close to Saturn's true color. It contains *lots* of interesting details. The south polar region looks rather interesting when viewed and illuminated from below. The rendering below has a latitude/longitude grid. The latitudes are planetographic:



The contrast is correct but I'm still working on the color so it is only approximate and should probably be more yellowish.

This is a contrast enhanced version without the grid:



Note the different appearance of the region south of 75°S from regions farther north, it has a different color and there are *lots* of bright spots there. Another feature I find especially interesting is that a part of the belt/zone boundaries near 60°S looks like the famous hexagon near Saturn's north pole. However, this is only a partial polygon, the most prominent 'polygon edges' are near pixels (547,139) and (742,218) but other edges are indistinct or absent. Two of the southern hemisphere's biggest spots are also visible near the edges of this image. They are located at 45°S. These two contrast enhanced images show them in detail:




The spots are similar in size and color/contrast but their shapes and immediate surroundings are somewhat different from each other.

EDIT: I forgot to mention that the images of the spots are in simple cylindrical projection with a resolution of 25 pixels/degree.

[Guest_AlexBlackwell_*]

Very nice work, Bjorn

[Nix]

Superb

Nico

[tedstryk]

Wow! That is some great stuff!

[4th rock from th...]

Can't wait to see the finished map!!!!