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Unmanned Spaceflight.com _ Cassini's ongoing mission and raw images _ NT Rhea Jan 17,07

Posted by: Decepticon Jan 18 2007, 04:15 AM

http://saturn1.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0

Some nice views.

Posted by: Ian R Jan 18 2007, 09:25 AM

Very nice indeed - here's a quick IR/G/UV composite:

Ian.

Posted by: Ian R Jan 18 2007, 09:32 AM

...and here's a version with the contrast stretched and the saturation increased:

Ian.

Posted by: ugordan Jan 18 2007, 09:37 AM

Very nice, Ian. This is one of those views that nicely captures Rhea's color dichotomy similarly to the recent Tethys images. There's a fair bit of color variation here, the wispy terrain being fresh/bluish while the dark stained hemisphere being reddish/greenish.

Posted by: Ian R Jan 18 2007, 09:40 AM

Last of all, with a 'Dodge' filter used on the Lightness channel to bring out detail in the bright areas:

Ian.

Posted by: Ian R Jan 18 2007, 09:45 AM

Thanks ugordan. Next to Ted, Bjorn and your good self, I am merely an enthusiastic amateur when it comes to Cassini imagery!

I wonder if the same event caused the dichotomies visible on Dione, Tethys and Rhea (perhaps Iapteus too)?

Ian.

Posted by: ugordan Jan 18 2007, 09:57 AM

I'm also only an enthusiast so we're on the same grounds here.
IIRC, the inner moons have stains on the trailing hemisphere while Iapetus is the reverse. Edstrick suggested a theory that it had to do with magnetosphere interactions with the surfaces. I'm not inclined to put Iapetus in the same basket as Dione/Tethys/Rhea as these have only a slight albedo variation, while Iapetus' dichotomy is orders of magnitude. Cassini Regio is also pretty well-defined, the other moons' splats are subtle and faint.

Edit: There's also a small Enceladus sequence that appears to be looking directly down on the tiger stripes. The distance is rather large, 660 000 km.
http://saturn1.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=96406

Edit #2: I've found a Rhea mosaic I made from PDS using stretched color, toned down to more natural colors that approximately shows the same view as your image. It can be found http://x5.freeshare.us/119fs229149.jpg. Of all the moons in the Saturnian system, I'm having the most trouble figuring out Rhea's exact color. VIMS was of little help because it was very noisy and useless. In rgb composites I get a creamy brownish color (with a touch of bluish streaks and that big crater splat) that is somewhat different than the single CICLOPS release. It's not too far off, though. As can be seen comparing Ian's composite with this mosaic, natural color differences are very subtle and the whole moon looks fairly dull.

Posted by: Phil Stooke Jan 18 2007, 05:54 PM

... and here is that Enceladus image after a bit of processing. This is enlarged 200%, and is a composite of four frames, each of which has been processed and sharpened a bit. Averaging four frames helps to reduce the JPEG artifacts etc. CP - this one's for you!

Phil

Posted by: volcanopele Jan 18 2007, 06:36 PM

LOL!!!

Low res, but still not a bad view of that region...

Posted by: angel1801 Jan 19 2007, 12:51 AM

I have just checked the raw image gallery and there is 12 more images of Rhea now. However these images are from about 604,000km out compared to the previous set which are about 474,000 km out!

Posted by: Decepticon Jan 19 2007, 02:57 AM

That reminds me of a Voyager Image.

Posted by: Phil Stooke Jan 19 2007, 02:30 PM

Here is a version of the new image sequence of Rhea. It is enlarged 200%, and is a composite of four frames, each individually processed before merging.

Phil

Posted by: alan Jan 20 2007, 05:28 AM

The last sequence in color (IR/G/UV)

Posted by: Decepticon Jan 21 2007, 07:54 AM

Nice Death sta.... I'm mean Tethys!

http://saturn1.jpl.nasa.gov/multimedia/images/raw/casJPGFullS27/N00075423.jpg

Posted by: mgrodzki Feb 10 2007, 03:51 AM

so… does rhea really have this color or is this false/enhanced here? all the images of rhea, dione and tethys i have ever seen all just look moon grey.

Posted by: Exploitcorporations Feb 10 2007, 04:03 AM

Yeah, I would say it's a bit enhanced, rather than false-color. It's great for showing the subtler variations. This is probably a little closer to natural, but not really accurate, just by reducing the saturation:

Posted by: Exploitcorporations Feb 10 2007, 04:16 AM

Tethys again on the last two periapsis passages:

Posted by: mgrodzki Feb 10 2007, 04:23 AM

yeah, im seeing in the tethys and dione threads that someone else already asked that and ugordan seems to confirm these are actual, even for other similarly dark regioned moons. i guess you see 1 color image of these moons for every 1000 black and white made me think that they didn’t have any color to speak of. and i also suppose on some of the opposite side views there might not be much color at all.

Posted by: mgrodzki Feb 10 2007, 04:10 PM

nice. wondering about the color variation on these moons from one side to the other and ugordan makes it all clear in one image.

is there the possibility to do the same for rhea and dione?

Posted by: ugordan Feb 11 2007, 02:17 PM

Here's a similar montage for Dione. This is based on stretched color so the colors aren't very accurate.

The dark, wispy terrain does have a greenish (!) tint to it, but it's more subtle in natural color views.