Padua Linea mosaic:Click to view attachment

Just for fun:Click to view attachment

No words, just great!!

What is that straight line in the bottom part of the second mosaic ?

Looks like the rings to me.

But which ring?

Crescent(no s--t, huh?):Click to view attachment

Exploitcorporations, your mosaics are really impressive... great job!
About SRFan question (which ring?), the answer is here:
http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=51438

SiguRosFan - I think the "ring" you asked about is the Enke Division. So you are not seeing a ring, per se, but an absence of rings.

Oops..... or all of the rings as the case may be.

I suspect dilo is correct. Since the spacecraft was close to Dione when it took the pic, it would have been nearly in the plane of the rings. Therefore the "rings" we see at the top of the image are the shadow of the rings on Saturn's cloudtops, and the "ring" we see at the botton of the picture is actually all of saturn's rings edge on.

9-frame globe:Click to view attachment

You clipped all the shadow detail!

Regional map:Click to view attachment

Trying to identify the locations of WAC and Saturnshine frames, as well as those last few NAC frames before the crescent mosaic. Maybe there's a better way to do this than visually? Any help would be appreciated.

Steve's map with WAC 00011127-00011130 & last frame of big regional mosaic:Click to view attachment

I'd think a way to approach it might be to use the SPICE kernels to get the instrument pointing as a function of time. It's possible to get the intersection of the camera boresight and the surface of the target (longitude, latitude) for any given time. That would give the lon/lat of the center of the image if the time that it was taken is known.

Unfortunately, the Cassini website doesn't give the time, just the date of each photo. But it does give the distance, so the spacecraft distance could be used as a proxy for the time. There would be some error, but it might give the location within a degree.

Thank you. I'm curious as to the exact process used by imaging scientists to construct the spectacular (and accurate) mosaics that are publicly released. As is certainly obvious, my own "handlaid" composites exhibit gross distortions and misalignments, particularly with global views(see the squashed-looking south pole of Dione above). I would imagine that the lat/lon centerpoints could be positioned on a spherical model and the individual images reprojected accordingly as they are placed.

I use the SPICE kernels and information provided to us where we download the raws (similar interface to the PDS) to navigate each image in a program called ISIS (publically available from the USGS website). I refine those solutions using a combination of limb fits, tieing to a basemap, or tieing to adjacent images. once I am confident that the lat and lons in my images are accurate, I can use ISIS to reproject each image to the same geometry. For the Dione and Tethys mosaics released recently, those are orthographic projections centered on the same lat and lon and with the same pixel scale. For public release products, I just piece these together in Photoshop, just to speed things along. I can also mosaic the images in ISIS, but often that's a slower process.

I must admit - doing mosaics with a combo of PTGui and Photoshop is a lot easier now Photoshop has the warp tool, very powerfull and usefull

Doug

Thanks for the fascinating primer. I must admit that my learning curve with image assembly has been a comedy of errors. I made my first composite in Photoshop last January(a crescent Iapetus), but only figured out how to use the transform feature shortly after the Tethys flyby( I stumbled upon the warp tool by using an unintended key combo). I spent roughly three years doing cut-and-paste Galileo mosaics with a printer and a stack of 14x17 "magnetic" photo albums. The only people who were remotely interested in this bizzare hobby were a couple of clerks at the local USGS map store, where I would occasionaly drag one of those ridiculouly massive albums for them to pore over. Photoshop is a little less messy...

Greetings,

I learned recently that there is a SPICE kernel interface for IDL on the naif.jpl.nasa.gov site. It could take me quite a while, yet this would be interesting to incorporate into my satellite mapping software. Then if I can set up a PDS/IMG interface I'd be all set...

BTW my latest Dione map update uses about as much of the released global (3x3) mosaic from the latest flyby as is reasonable. Now I can consider whether to include some of the regional imagery.

http://laps.fsl.noaa.gov/albers/sos/sos.html#DIONE

A few of the southern high-resolution frames(updated).
Background mosaic by NASA/JPL:Click to view attachment

Beautiful view of Dione at low phase angle, taken from 1425000 Km on 23MAR2006/20:02:18 UTC
(clear background should be E ring...)
Click to view attachment
Original images:
luma channel: N00055875.jpg (clear filter)
chroma components: R=N00055873 (MT2), G=N00055874 (G), B=N00055873 (UV)

Here's an update on the D1 encounter last October, looking at the context for crescent and Saturnshine observations following closest approach. Thanks to Steve Albers for your astonishing maps and Chris Laurel for Celestia.


Amata mosaic:Click to view attachment


Broad context:Click to view attachment

High resolution frames: Click to view attachment

Crescent mosaic (apologies to um3k for first attempt):Click to view attachment

Full context:Click to view attachment

Totally excellent, dude!

Just a heads-up for the rev after next...it looks as though Cassini will have an outstanding moderate-resolution view of pretty much the whole fracture system, as well as additional gap fill coverage to the north. This view of Dione on 24 July 2006 from Celestia's reference trajectory is from a distance of 260,000km, the field of view narrowed by a factor of two for visibility.

Click to view attachment

Using the Solar System Simulator, I also have some good imaging opportunties for Dione:

November 20, 2006 (260,000km)

Good imaging of the moons south pole area as a crescent (like Iapetus on April 11, 2006!)

September 30, 2007 (78,000km)

The entire saturn facing hemisphere is sunlit!

Some compositions ...

Has anyone noted tthe CASSINI CHARM presentation from 06/29/06?

"Magnetic Portraits of the Icy Satellites of Saturn"

Slide 27 to 32 and slide 45 conclude there is mass-loading at Dione so there may also be plume activity from this moon as well as Enceladus. The Dione mass-loading is an order of magnitude less than the Enceladus mass loading but the the team feels sure this is a REAL event.

Very cool and maybe we should be looking for some very faint plumes at Dione.

Also interesting that Dione and Enceladus both appear to have the greater density of any of the mid sized moons.

Sorry all... the date on the presentation web site is 05/29/06...... I fumble fiingered ....

Also, these image mosaics are just awesome..... congrats to all.................

All.... trying to do this from work and keep forgetting things I meant to add in the first note I posted...

Here is the presentation I was talking about ............

http://saturn.jpl.nasa.gov/multimedia/prod...ARM_Krishan.pdf

Dione ....... a scent of water/nitrogen perfume still wafting the Saturnian system????

Yeah, I pointed this out here http://www.unmannedspaceflight.com/index.p...ost&p=55911

I thought it was pretty cool too, but the response seemed to be deafening silence.

Bart

Fantastic work. Might I suggest changing your name to Exploitphotomosaics ?

I did read that, but didn't get back to the thread...

"Curiouser and Curiouser, said Alice"

Dione has higher density than most of the small moons, doesn't it?.. more isotope heat..

It's the only moon other than the hot enchilada with relatively pristine fracture patterns.

It has flat areas largely lacking large impacts and they seem relatively textureless other than smaller impact crater populations... as though they'd been resurfaced.

Isn't Dione the sat in a resonance with Enceladas?

It'd be the only other candidate in the system for any internal heating driven outgassing, "fer sure". Tethys had activity and resurfacing but looks pretty thoroughally dead now.

The Dione images were successfully taken and transmitted to earth and the 11 images are available as raw images. Also there are some good images of Rhea's south pole area in a crescent position from about 170,000 km out too.

After watching these pictures I'm still wondering about the reality of the Amata basin.
These pictures as well as most of the pictures of the same region taken with a lower resolution (Voyager 1 included) seem to show that it indeed exists. However, the high resolution pictures (which were all taken at low sun angle) do not show any trace of the basin. After the close flybys I was convinced about its non-existence, but now, I again have a doubt. So could it be a kind of palimpsest indicating a very old basin almost erased by the younger overlying tectonic patterns or is it just an optic illusion due to fortuitous placing of tectonic, impact and albedo features ?

I made this pseudo color (MT2+CL+UV filters) of last Dione view and only now I noticed the stright, narrow, bright features in the right/bottom region. Some of them clearly originate from a common point (impact?)...
Can someone explain these "channels"?
Click to view attachment (normal version)
Click to view attachment (enhanced version)

They were originally thought to be crater rays and named Cassandra. Current theory says that they're a system of radial fractures and scarps.

Michael

Thanks Michael; this is amazing and recall me Europa, even if here channels aren't curved...

Dilo,

Here's a couple of earlier Cassini pictures of Dione that show Cassandra to good effect:

http://saturn.jpl.nasa.gov/multimedia/imag...3/N00037561.jpg

http://saturn.jpl.nasa.gov/multimedia/imag...1/N00035168.jpg

And here's a PDF discussing the origin of the feature:

http://www.planetary.brown.edu/m42/m42_68.pdf

Cheers,

Ian.

Wow, this "wispy material" could be a surficial deposit associated with (cryo)volcanic exhalations along cracks!
Thanks, Ian.

Yeah, when you look at the lines in detail, it appears that there may have been upwelling along the thicker portions.

These do look more like cracks than rays, don't they? They are emplaced radially, and would seem to have been caused by some type of impact at the center of the radia. You'd think the surface would only do that if it were a fairly thin layer of ice floating on a liquid ocean, wouldn't you?

-the other Doug

I might have looked instead at diapir effects - let's say Cassandra marks a diapir that stalled, just producing a few radial cracks, while the main fracture system was produced by a major diapir-induced uplift, lots of basically radial fractures in broad lanes, plus a bit of central subsidence as the process ended, producing Amata. I think an impact would be more obvious.

Phil

Is there any chance that Dione is still active ? I would not be so surprised.
I heard about rumors of plumes. Does anyone know more about that ?
Dione is for me the third most interesting moon of Saturn (after Titan and Enceladus of course), far more interesting than the curious but likely old and frozen Iapetus. The tectonic features appear to be really "fresh" (as it seems to be also the case for the giant basin near the south pole).

Any one look at the current CASSINI RAWS.....

probably just my bad eye eight (or blurry glasses), but I think I see a hint of diffuse activity along Dione's
crescent in this image.........

http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=80462

Again..... see my earlier post to this thread regarding the CHARM presentation. Mass loading at Dione
was detected and the team suggests looking for plume activity...... wonder if this set of images is an attempt to do just that?????

Craig

Thanks Graig. It was indeed in your earlier post regarding the CHARM presentation that I heard about the possibility of a dionean plume. But no other info about it anywhere else.

Concerning the crescent picture, I can also see a kind of "hazy feature" above the limb. But it's really difficult to conclude. Moreover, it's not apparent in the second picture (artefact or different viewing angle ?).
It would be so great to detect a current active Dione !!

Marc.

That's definitely looking like a scattered light artifact. It appears right below the thickest and brightest part of the crescent. These are probably just optical navigation images, the phase angle isn't all that favorable for a plume search.

I have to agree with ugordan, following elaboration with negative/smoothed weak details show that there isn't any trace of extended plume "à la Enceladus".

Thanks for the comments MarcF, ugordon, and dilo....

Have to "kinda" agree. Wondered if the other image was taken at a slightly different exposure setting.

The CHARM presentation says the mass loading at Dione is an order of magnitude below what is seen at Enceladus. So I picture that as, perhaps, diffuse shedding of internal gassy molecules. It may not show up as a distinct plume. It may be distributed along the fracture systems......

What was the geometry of the Dione 16 encounter? What longitudes did that cover at closest approach?

Craig

Another couple of false color elaborations based on a sequence of increasing exposures, clear filter images:
Click to view attachment Click to view attachment (start images: N00064540/41/42)
First one associate an RGB channel to each image while in the second one I tried to highlight dimmest details.
To highlight the small difference between position angle of subsolar point and the faint glow, which seems slightly rotated toward left (the difference is about 20 deg, measured from Dione center).
Again, not enough to say if there is a weak plume or an artifact but seems interesting...