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Unmanned Spaceflight.com _ Cassini's ongoing mission and raw images _ Rev21
Posted by: Decepticon Feb 25 2006, 12:43 AM
Raw images started. Rhea! http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0
Posted by: Decepticon Feb 25 2006, 01:17 PM
More great images... http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0
I hope cassini imaged Tethys. I'm looking forward to seeing the polar areas seen poorly until now.
Posted by: ugordan Feb 25 2006, 03:36 PM
Rhea exaggerated color composite from 350 000 km:
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Posted by: David Feb 25 2006, 04:02 PM
Nice. Very interesting to see the ray system almost head-on, too.
Posted by: dilo Feb 25 2006, 08:48 PM
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I made something similar with previous images taken 3 times farther (right color enhancement, image is sharpened too):
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Posted by: dilo Feb 25 2006, 09:17 PM
I hope cassini imaged Tethys. I'm looking forward to seeing the polar areas seen poorly until now.
Here polar regions aren't very visible, but Thetys emerging from partially shadowed rings is truly amazing!
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS18/N00051353.jpg
Posted by: dilo Feb 25 2006, 10:40 PM
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS18/N00051353.jpg
And this is the animation! (different filters, so do not care for apparent rings bightness variations):
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Posted by: Decepticon Feb 26 2006, 03:49 AM
As nice as they are I expected better images!? Maybe they will come in the next upload batch.
Posted by: tedstryk Feb 26 2006, 04:28 AM
Great work!
Posted by: dilo Feb 26 2006, 07:28 AM
Thanks, I forgot to say that it was a false color image based on MT/G/UV filters.
Posted by: volcanopele Feb 26 2006, 05:30 PM
I've moved the posts regarding images from Rev21 (~late February 2006) to this thread.
Posted by: Phil Stooke Feb 26 2006, 05:57 PM
I've been very impatient for the first look at Helene. Here it is... a composite of six images. Saturnshine illuminates the right side. Another smoothy.
Phil
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Posted by: Decepticon Feb 26 2006, 07:46 PM
Saturnshine is a Lovely word! Nice!
OH JOY! Tetheys!!!
I can't wait to see Steve Do his magic!
http://saturn1.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0
Posted by: dilo Feb 26 2006, 10:59 PM
Amazing view.
Very rough pseudo-color composition (IR+CL+UV)...
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Posted by: Exploitcorporations Feb 27 2006, 12:50 AM
Tethys through the clear filter at 153,000km:
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Posted by: Phil Stooke Feb 27 2006, 03:53 AM
Excellent Tethys mosaic!
This image is derived from ugordan's Rhea color image... I used Photoshop's spherize filter (twice) to convert the map projection from orthographic to stereographic (approximately speaking). See how craters that were very foreshortened along the limb are made nearly circular in this projection.
Phil
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Posted by: edstrick Feb 27 2006, 07:28 AM
Phil: I've long thought a good way to handle distant moon and planet images was to convert them to a stereographic projection. For "extract all you can" processing... apply some procedure that estimates the fraction of limb-containing pixels that are off-disk and correct them to a best estimate "on disk" brightness. Then project to stereographic.
Calculate several overlay map-images for each stereographic image: Incidence angle, emission angle, pixel-size-in-km and phase angle. Using the geometry map-images and photometric functions, photometrically correct the images for incidence/emission/phase, and generate a quality weight for each pixel:
Transform the images and the weighting masks into map projection. Multiply each image by it's weight mask and sum. sum each weight mask and divide the final summed map by the weight map to get optimally weighted mosaics.
For colorimetry, weight is maximum at 0 deg normal incidence angle and zero at 90 deg terminator data. For relief mapping, weight is maximum at (maybe) 75 deg incidence and goes to low values at normal incidence and terminator (all shadows) illumination. Etc.
Nice shot!
Posted by: ugordan Feb 27 2006, 10:20 AM
Several Titan NAC raw frames are already down, taken from distant 400 000 Km. Most likely they're part of the ISS_021TI_GLOBMAP001_VIMS observation and downlinked during the first radio science pass.
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=64420
Edit: Hm... this probably belongs to the Titan forum... Duh!
Posted by: Exploitcorporations Feb 27 2006, 11:12 AM
Here's a Rev 21 Tethys grab bag:
RGB composite overlay(crude):
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Analgyph:
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Spherized(thanks, Phil!):
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Basin:
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Perspectives of Tethys, 2004-2006(representative):
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Posted by: Phil Stooke Feb 27 2006, 01:50 PM
This really belongs in the 'reprocessing historic images' thread, but I'll be naughty and post it here (spank me!)
Tethys from Voyager 1... I'm posting it to show another view of the craters in this area.
First, you can see the large southern craters, and even the big but very subdued basin north of the really big one (whose name is Melanthius). They are not new discoveries.
Second, look at Penelope, the large crater in the middle of the disk. Very prominent in one image, invisible in the next (and well seen by Cassini). Why does it disappear? In the left-hand view the shading is albedo, not topographic shading. It just happens that the albedo and topographic shading cancel out in the right-hand view (think about how the sunlight falls on the crater walls). But also, see how Penelope falls on the border of a dark stripe, one of two on Tethys. Its pattern of light and dark is like the craters at the edge of Cassini Regio on Iapetus. Whatever explains Cassini Regio is presumably at work here. This is the best example, but not the only one, on Tethys.
Phil
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Posted by: tedstryk Feb 27 2006, 03:39 PM
I am a bit confused. I have worked with the V-1 sequence, and the crater gets fainter, but I can't find the frames in which it disappears. 
Posted by: Phil Stooke Feb 27 2006, 05:45 PM
It's 349073, the one after your left-hand image here.
Here is my set of Voyager images of Tethys:
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Specially processed to enhance both topography and albedo.
Phil
Posted by: ugordan Feb 27 2006, 11:23 PM
I tried producing a color image of Helene, but to tell the truth -- the thing is as white as can be.
The left image is approximately true color using R/G/B filter combo, the middle is stretched color using IR1/GRN/UV3 filters and the third is the RGB image heavily color saturated to bring out very subtle color differences. The same result turns up if using the stretched color so I omitted it.
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As can be seen, the surface seen in visible wavelengths is very uniform and bland.
Posted by: Decepticon Feb 27 2006, 11:33 PM
Just noticed this... http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS18/N00051445.jpg
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?StartRow=17&cacheQ=1&browseLatest=0&storedQ=1192479
Posted by: Decepticon Mar 2 2006, 12:35 AM
Steve Albers has updated his Tetheys Map. http://laps.fsl.noaa.gov/albers/sos/saturn/tethys/tethys_rgb_cyl_www.jpg
Steve can previous post help with the mapping? It has some areas that can fill in some lower resolution areas.
Posted by: Phil Stooke Mar 2 2006, 02:00 PM
Steve's map of Tethys is very nice, as usual. Here are polar hemisphere versions of it - to be precise they are azimuthal equidistant projections, parallels of latitude are equally spaced.
Phil
north:
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south:
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Posted by: scalbers Mar 2 2006, 11:30 PM
Steve can previous post help with the mapping? It has some areas that can fill in some lower resolution areas.
This indeed is worth a try Decepticon. It looks to provide new details in the northern and eastern portions of the image (from post #24). Even with the lower phase angle and muted contrast I can see it will be helping with the map.
I'm also working on various adjustments to image brightnesses, navigation, etc. so I hope to post one or more updated versions in the upcoming days.
Interesting (as always!) to see Phil's polar projections as well.
Posted by: dilo Mar 5 2006, 02:27 PM
Again on Helene imagery...
I processed the 6 frames from green/CL filters, using Registax for stacking and for detail enhancement (I'm just a beginner with this powerful software, but results are very encouraging 
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Then I used UV/IR in order to have also a color version, but I had to enhance saturation (as ugordan):
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I made also a low luminosity enhancement of the B/W stacked image, in order to show faint details as already done by Phil (colors are due to different gamma curves assigned to the 3 components, not real!):
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Note: images are enlarged by 50% from original, so scale should be 270m/pixel.
Posted by: tedstryk Mar 5 2006, 10:06 PM
I processed the 6 frames from green/CL filters, using Registax for stacking and for detail enhancement (I'm just a beginner with this powerful software, but results are very encouraging
). Then I used UV/IR in order to have also a color version, but I had to enhance saturation (as ugordan):
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I made also a low luminosity enhancement of the B/W stacked image, in order to show faint details as already done by Phil (colors are due to different gamma curves assigned to the 3 components, not real!):
Note: images are enlarged by 50% from original, so scale should be 270m/pixel.
If they release a b/w version that isn't autostretched on the photojournal, it would be neat to overlay your color version on top of it.
RGB composite overlay(crude):[
Analgyph:
Spherized(thanks, Phil!):
Basin:
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Perspectives of Tethys, 2004-2006(representative):
Very nice!
Posted by: JRehling Mar 6 2006, 04:59 AM
The Lagrangian satellites continue to appear very smooth. Is it possible that particles in other orbits "snow" out onto them? If so, they should look smoother than very small satellites in other orbits. Radar could say something about comparative smoothness... I don't know if it would be possible to do that from Earth, since only a point observation is needed.
Posted by: dilo Mar 6 2006, 06:50 AM
In fact, autostretch make impossible to establish the real hue of the satellite... we can only say somenthing about color differences in various regions.
Anyway, I repeated previous work on the RGB pictures and results are showed below; now colors appear different!
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I suspect that feature in the top could be a huge crater rim, with central peak emerging from the darkness...
Posted by: Phil Stooke Mar 6 2006, 02:02 PM
Two replies... to JRehling about radar from Earth - they couldn't get enough return frrom a tiny satellite to make that work. Bistatic radar from Cassini might be possible (but very unlikely as geometry has to be perfect). But I think photometry (phase function) is really the key to doing this, and it will be easy with lots of images throughout the mission.
And to Dilo - I also think the top of the Helene image is a biig crater - don't agree about a central peak, though. But this is almost the same view as the one from Voyager 2, if I'm not mistaken, and that shows the crater nicely.
Phil
Posted by: scalbers Mar 9 2006, 11:06 PM
Greetings,
I've been updating my Tethys map along the lines of the discussion on post #27. This version also shows a bit more of the far southern crater that was near the limb in a recent NAC image.
http://laps.noaa.gov/albers/sos/sos.html#TETHYS
Posted by: angel1801 Mar 10 2006, 12:36 PM
I've been updating my Tethys map along the lines of the discussion on post #27. This version also shows a bit more of the far southern crater that was near the limb in a recent NAC image.
http://laps.noaa.gov/albers/sos/sos.html#TETHYS
I was using the "Solar System Simulator" just a little while ago, looking for chances for Cassini to image Tethys's south polar region. I Found one.
Cassini pretty much directly over Tethys SP area (just like it was on May 2, 2005) at a distance of about 202,000km on November 9, 2006 at about 01:00 UTC. This should give about 1.5km/pixel resolution over all of this area.
Posted by: scalbers Mar 11 2006, 01:10 AM
Sure enough angel1801, here is a simulated image using Celestia at this URL:
http://laps.noaa.gov/albers/sos/saturn/tethys/tethys_celestia.jpg
Here the relatively blank areas in the map represent good news as we'll get some first looks at new details on Nov 8-9, 2006.
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