[X] My Assistant

[ugordan]

A great Rhea multispectral set recently came down, taken from a distance of around 245 000 km. Here's a RGB composite, Rhea really fills the NAC field of view in this one:

[Mariner9]

These RHEA images are great! Everyone please take note of the prominent geologic formations on the limb.

R-r-r-r-r-r-rhea's got R-r-r-r-r-r-r-ridges !!!!!!!!!!!!!!!!!!!!!!!

Correct me if I'm wrong, but this is the first direct confirmation that the "whispy streaks" on Rhea are similar to Dione's ice cliffs.

[Rob Pinnegar]

Yeah. Good to finally see some evidence of SOME kind of activity on Rhea, even if it just be old grabens and some cracks.

[Steve G]

Yeah. Good to finally see some evidence of SOME kind of activity on Rhea, even if it just be old grabens and some cracks.

I was wonderingif that old Voyager 1 picture showing the streaks was a practical joke!

[tedstryk]

I was wonderingif that old Voyager 1 picture showing the streaks was a practical joke!

This image shows the cliffs very well. Unfortunately, it was a lone opnav while Voyager 1 was approaching, so super resolution is not possible.



Also, here is a sequence from Voyager 2. The images are shown in the order they were taken. Some are larger than others because when multiple frames were availabl, super resolution was applied. When they were not, images were shown at their size. But sequentially, they are in order. And as can be seen, the streaks become obvious as creacks as they approach the teminator.

[David]

A great Rhea multispectral set recently came down, taken from a distance of around 245 000 km. Here's a RGB composite, Rhea really fills the NAC field of view in this one:

What's the straight line slanting across the lower-left-hand quadrant? Surface feature or image artifact?

And doesn't Rhea have some pretty darn huge basins, even if they are in low relief?

[Michael Capobian...]

Well, it's on both the Voyager image above and a number of Cassini images, so it's real enough. If the lines radiating from Cassandra on Dione are in fact scarps, as per http://www.planetary.brown.edu/m42/m42_68.pdf, it's not to difficult to imagine that this straight line is as well. But there are a number of straight lines on these moons, and not all of them can be explained that easily.

Michael

What's the straight line slanting across the lower-left-hand quadrant?  Surface feature or image artifact?

And doesn't Rhea have some pretty darn huge basins, even if they are in low relief?

[ugordan]

What's the straight line slanting across the lower-left-hand quadrant?  Surface feature or image artifact?

No, that's not an image artifact. A similar feature was seen in images taken months ago, see this CICLOPS release. I believe the feature itself is curved, but the viewing geometry makes it look straight. It's interesting that two different views produce a straight line, though I don't know if it's the same feature -- Rhea might have more than one of these linear features.

EDIT: On closer inspection, it turns out the above composite image and the CICLOPS release have a remarkably similar viewing geometry, that is, sub-spacecraft point. The only thing different is the illumination angle so it's not at all surprising the feature turned out to be straight in both images. Ted Stryk's larger image also shows the linear feature and due to a different viewing angle it's clear that it is in fact curved.
Talk about interesting coincidences...

[jmknapp]

Does anyone know the three moons in this grouping:

http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=62180



Rhea, Mimas & ????

[ugordan]

Does anyone know the three moons in this grouping:

Rhea, Mimas & ????

Enceladus.
JPL Solar System Simulator gives this result, obviously a couple of minutes after the Cassini image was taken.
Enceladus is the one more illuminated by saturnshine and farther from Rhea in that raw image.

On a side note, the new CICLOPS release shows a really perplexing trend in releasing only grayscale images when multispectral sets were obviously taken. There were a number of color composites ("natural" and enhanced color) by us amateurs a month ago and it doesn't really take more than 15 minutes to create such a composite. It's not like they have to be scientifically accurate, the imaging team clearly stated these images are for public purposes only anyway.
Why, then, the insisting on dull grayscale images? I know the moons are really bland in reality, but give me a monotone color image over a grayscale any time. It's as though the team are releasing these images against their will so they don't even bother with cool pics most of the time.
Not that there haven't been very spectacular releases, mind you! It's just that most of the time these releases tend to be routine-ish and hardly awe inspiring...

I'm sure I'll get bashed by volcanopele for this

[Fraggler]

On a side note, the new CICLOPS release shows a really perplexing trend in releasing only grayscale images when multispectral sets were obviously taken. There were a number of color composites ("natural" and enhanced color) by us amateurs a month ago and it doesn't really take more than 15 minutes to create such a composite. It's not like they have to be scientifically accurate, the imaging team clearly stated these images are for public purposes only anyway.
Why, then, the insisting on dull grayscale images? I know the moons are really bland in reality, but give me a monotone color image over a grayscale any time. It's as though the team are releasing these images against their will so they don't even bother with cool pics most of the time.
Not that there haven't been very spectacular releases, mind you! It's just that most of the time these releases  tend to be routine-ish and hardly awe inspiring...

'Scientifically accurate' no, *calibrated* yes. Also when we ametuers put images together it's just that... CICLOPS has to draft captions and get those captions approved by NASA HQ.

There are also a lot more ametuers than there are image processors.

[JTN]

On a side note, the new CICLOPS release shows a really perplexing trend in releasing only grayscale images when multispectral sets were obviously taken.

saturn.jpl.nasa.gov has some false-colour versions of recent icy-satellite releases where ciclops.org does not, for some reason. (There's no colour variant of the Rhea image you link to, but there is of one other Rhea image + two Dione images.)

[JTN]

Does anyone know the three moons in this grouping:
http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=62180
Rhea, Mimas & ????

FWIW, here's a quick'n'dirty animation of the frames around this one (N00049532-N00049570).
(There are some earlier ones, N00049514-N00049531, but with them there'd be a jump in the animation.)

BTW, your analysis tool does a nice job on these.

[volcanopele]

saturn.jpl.nasa.gov has some false-colour versions of recent icy-satellite releases where ciclops.org does not, for some reason. (There's no colour variant of the Rhea image you link to, but there is of one other Rhea image + two Dione images.)

Actually, the CICLOPS pages for those images have both the greyscale view and the false- or enhanced-color views for those releases that have both. Just click on the text link and not the image to bring up the caption and both views.

[ugordan]

Actually, the CICLOPS pages for those images have both the greyscale view and the false- or enhanced-color views for those releases that have both.  Just click on the text link and not the image to bring up the caption and both views.

While you're here, can you tell us a ballpark figure on how long it takes to produce one such image? I'm referring only to image processing, not writing an advisory that has to get past NASAs PR office and stuff like that.
Just the actual image work?