I was struck by how much images like this...

http://saturn.jpl.nasa.gov/multimedia/imag...5/N00148493.jpg

... remind me of the view through my 4.5" scope when I peer into it without the eyepiece. LOts of fascinating internal light reflections there...

Looks like someone's been hunting for Iapetan moons again...

Prometheus at last seen at close range.
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and
Click to view attachment

Raw close-up pics now (finally) available of Prometheus, courtesy of Rev 124

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=210215
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=210303

I know i've been hanging out for close pics of this rock, being the last of the big(-ish) inner rocks to be imaged up close-ish (good pics already of Janus, Epimetheus & Pandora). I'll bet i'm not the only one

Now that Cassini is no longer orbiting in the ring plane there are some interesting images of the spokes:

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=210366
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=210363
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=210360

Soon there will be exactly one Saturninan year from the Voyager 1 flyby.

Check out Enceladus!
http://saturn.jpl.nasa.gov/multimedia/imag...6/N00148932.jpg

and talk about high phase!

http://saturn.jpl.nasa.gov/multimedia/imag...6/W00062176.jpg

ROFLMAO, thank you for also posting the WAC view. I just about had a heart attack when I saw the NAC image.

Awesome Prometheus images, a quick RGB composite from the first set:
Click to view attachment Click to view attachment

EDIT: Added 2nd, lower phase set as well.

I'm still trying to deal with all these noise hits... darn you charged particles, why do you pain me so?

Man, that is one ugly space rock. It looks like some kind of mutant tuber.

It's not ugly. It's got character.

It's also apparently got a lot of ring material deposition, though seemingly not as much as Atlas.

And, not surprisingly, its craters appear to be more "eroded" or rather covered in dust than Pandora's craters.

You know, that's an interesting point. I wonder how much real erosion of surface features on these ring rocks does actually occur via this process vs. just coating everything.

Probably not much, but it's definitely a factor in play.

Perhaps we have an ongoing process of gradual deposition (precipitation?) interrupted by the occasional thwack of an impact knocking off most of it . . . . .

Or maybe mag field effects zorch some off when the field flips or Saturn passes thru the Jovian magneto tail.

The image is terribly noisy, but you can see the shadow of the moon in the F-ring.

http://saturn.jpl.nasa.gov/multimedia/imag...6/N00148979.jpg

[quote name='ugordan' date='Dec 27 2009, 01:08 PM' post='152478']
Awesome Prometheus images, a quick RGB composite from the first set:

Very nice. I was wondering what you're basing your color balance on. I did an RGB combine after cleanup and alignment in MaxIm DL5, and I end up with slightly more color variance across the little icy rock. My version also uses a touch of non-linear stretching so that the bright regions are easier to see. Upsampled and slightly deconvolved (0.5 PSF, 4 iterations).Click to view attachment

Sean W.

I based it on the F ring white point which in principle should have also resulted in Prometheus' color being close to some calibrated shots I have (this one and this one) - a slight brown-reddish color. Mind you, I did this on a laptop screen and I have no idea if it turned out remotely close to what I wanted it to. There definitely is some slight color variation, but just like in Hyperion's case, if you don't "kill" the overall hue, it's not noticeable. Otherwise you just have red and slightly-less-red regions.


Do you use any special tool for that? I'm asking because I'm looking for a more specialized deconvolution tool than the "smart sharpen" filter in Photoshop for Deep Impact imagery.

Thanks, I'll try that. I use MaxIm DL CCD 5.08 for resampling and deconvolution. It includes Richardson-Lucy and Maximum Entropy algorythms, though R-L (or as others call it, LR) is the better version, based on the code developed to fix Hubble images before COSTAR.
http://www.cyanogen.com/maxim_main.php
You can download and try the program free for 30 days. It is pricey though. Another alternative is a plugin for Photoshop called Focus Magic. Google it. It works well also, though not nearly as powerful.

I use LR often with my amateur astrophotography to deal with my usual poor seeing conditions:

http://masil-astro-imaging.netfirms.com/Solar%20System.html

http://masil-astro-imaging.netfirms.com/Latest_Images.html

I cheat to get color. RGB color combos from Cassini images almost always have some completely white pixels due to the automatic stretching. To set the color I just go grab something Gordan made from calibrated imagery and set the RGB values of that brightest pixel to those of a bright pixel in a Gordan image. It's not science but then images made from raws aren't science either.

Also for the version I posted in the blog I made an RGB combo from red, green, and blue filter images, and also stacked the red, IR, clear, and green channel images to make one that was less affected by JPEG artifacts and noise, then did a nonlinear stretch on it to bring out some more of the detail in the brighter regions, then sharpened it just a little bit. Then I converted the RGB to HSB and swapped in the sharpened image for the clear channel.

Thanks for the insights. This is probably closer to accurate then.Click to view attachment

Which is kind of similar to what I did above - selected a small rectangle (for better s/n) in the thick of F ring, removed "dust and scratches" and averaged it and thus got the white point and channel balance, seeing how much each channel needs to be boosted to make that averaged portion gray. In 16 bit mode, of course, every little bit helps. Then just applying those factors to the entire composite. Obviously only works if you have something you know is pretty much white/gray in the source image AND is not overexposed in any channel - F ring, Mimas, Enceladus and leading hemispheres of Tethys and Dione work well here.

When it comes to raw jpegs, we all cheat. Only our methods may differ

Though we tend to come to similar conclusions. If you decide to try MaxIm, feel free to ask me any questions you'd like via my Sky & Telescope email address.

Happy new year!

Very interesting first images from a reasonable range. Prometheus is much closer to Pandora than Atlas in a superficial visual sense.
I was expecting to see much more ring-deposited material - at least on the anti-saturn end of the moon, especially since the satellite regularly dips into the core of the F-ring.
Nice to still be surprised by the Cassini results.

Jase

as long as things like this are at a min. and do not take over a thread ...
there as always a bit of room for some late night ( 4 am) fun . but i did like the Santa and raindear in front of saturn .

One of UMSF's alumni makes a contribution in this MSNBC article

Right on...congrats, Emily!!!

Awesome!

I hate being on vacation - I can't play with all these new goodies!

Phil

A crescent Saturn, taken on the 2nd of January:

Click to view attachment

Happy New Year to everybody!

It could have been much worse... Actually, Cassini data indicate that Saturn's radiation belts are much weaker than any other in our solar system. The moons and the rings material do a very good job in removing lots of this noise source for the images :-)

I didn't notice anyone else commenting on this - but the Prometheus images show the side opposite the best Voyager view, and north is at the top in the raws.

Phil

I just love abstract images like this....
Click to view attachment

I won't claim that these are anywhere close to true color.
Full res of this image on flickr here: http://www.flickr.com/photos/31678681@N07/4246131869/
Another in this sequence here: http://www.flickr.com/photos/31678681@N07/...57622089931268/
Two frame composite: http://www.flickr.com/photos/31678681@N07/4246158737/

and we get a repeat performance on Jan 27th, the phase is a lot higher (80-125 deg) while the range is ~ 33-38,000 km.

Sweet! Aren't there a passel of other moons being imaged on the 27th? JPL's space calendar has "Jan 27 - Cassini, Distant Flyby of Telesto, Methone, Pan, Prometheus, Aegaon & Dione"

Going by information elsewhere on the forum, Cassini passes the following moons at reasonably close distances on 27th January. I have no information as to whether the moons are in eclipse at closest approach, whether imaging is planned, or whether other science activities/downlinks take preference at the time. Pixel values assume imaging bang-on closest approach. I would imagine Dione and Prometheus will be imaged, but smaller 'rocks' probably doubtful.

Pan: 95,233km - 54 pixels in the NAC at closest approach
Prometheus - 30,492km - 546 pixels
Aegaeon - 13,305km - 6 pixels
Methone - 74,527km - 7 pixels
Telesto - 95,643 - 42 pixels
Dione - 46,805km - more than 1 NAC frame

Jase

These two sound like particularly nice opportunities.

Anyone wanna improve the Voyager map Phil made with these Cassini images.

And Prometheus has a seemingly smoother surface than its twin Pandora
maybe its because of its larger size causing it to interact more with the F ring.

being on the surface of Prometheus is probably like being in a hailstorm.

Antdoghalo--Improving on Phil's maps is not a trivial challenge. While many here at UMSF have excellent image manipulation skills, the number with Phil's map making skill is vanishingly small. I would encourage you to work on your own challenge. Maybe after hundreds of hours of map making and manipulation, you can develop into a top flight map maker yourself.

Well, thanks! But the biggest obstacle is the lack of a proper 3D shape model. With this new data set and the new one in a few weeks, and any others Cassini might provide, we can hope to create a really good shape model in a few years. It would still be possible to play around with some sketch maps even now, though I'm too busy to do much with it.

Phil

The moons that will be imaged on Jan 27th are Prometheus and Aegaeon, as part of a single combined Prometheus-Aegaeon- G ring arc observation, and then two separate Dione obs later on in the day.

Actually there is a dedicated Aegaeon observation before that one, during the ring plane crossing (it's just named funny).

Oooh! Lots of goodies coming up!! Thanks Pat and VP.
January 27th will be an interesting periapse.
Any Aegaeon obs. will be too distant relative to the tiny moon to reveal any surface details, but we should get an idea of its shape.
The Prometheus pictures should provide coverage which matches the best Pandora data, and the Dione encounter leads in from the moon's nightside- perhaps an opportunity to detect some minimal outgassing if present???

And if that wasn't spoiling us enough, we get a targeted encounter with Mimas on the following revolution approaching to less than 10,000km - a flyby where we finally get to have a good close look at Herschel....

Great times!!

Wow:

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=211928
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=211933
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=211937

Is that F-ring's shadow draping across it?

Here's a hint of what's hiding in the shadows...

Phil

Click to view attachment

Click to view attachment

Aha! I KNEW it! Saturn's small moons are covered in jpeg compression artifacts!

A cleaned-up view of the end facing the F ring. There's a hint of lineations near the bottom, and a smooth area in the middle. I expected a smoother surface.

Phil

Click to view attachment

Looks like a ringshadow!

Click to view attachment

Here's an animation consisting of six NAC frames that show the shadow of the F-ring moving across Prometheus. Some spacecraft movement is evident too.

Click to view attachment

That wasn't 'spacecraft movement', that was the shock wave from my jaw hitting the floor. Every time I think "That's one of the coolest things I've seen on UMSF!" someone posts something like that...!

The wonders we're seeing... just incredible...