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Posted by: volcanopele Jul 27 2005, 09:32 PM

Now out of solar conjunction, we can now look forward to the next Cassini of Mimas next Tuesday. During this flyby, Cassini comes within 62,000 km of the surface on Mimas at 9:49 PM PDT August 1. This will be the best Mimas opportunity of the tour. Views from the Solar System Simulator are suspect since they have not incorpated the "Tethys tweak" change to the tour, which raised the Mimas flyby altitude from 49,000 km to 62,000 km. However, they show that at C/A, Mimas should be in moderate phase observations over Mimas' trailing hemisphere. A few hours before C/A, 1.2 km/pixel scale imaging should be possible showing Herschel near terminator.

Should make for a very exciting flyby.

Posted by: Sunspot Jul 27 2005, 09:58 PM

Ahhhhhhhh........thats why there haven't been any new images for a while. I should check my Starry Night software more often.

Can't wait to see Mimas

Posted by: Bjorn Jonsson Jul 29 2005, 02:20 AM

I did an animation showing the upcoming Mimas flyby:

http://www.mmedia.is/bjj/misc/css_stuff/rev_012/mimas_rev012.avi (warning: almost 7 MB)

It runs from August 1 2005 22:46 UTC (200,000 from Mimas) to August 2 2005 11:33 (also 200,000 from Mimas) and has a field of view of 0.35 degrees - identical to Cassini's narrow angle camera. The closest approach of roughly 63,000 km should occur on August 2 2005 near 04:24 UTC.

Posted by: Decepticon Jul 30 2005, 04:05 PM

I hope we get some night side imaging. Than again maybe cassini will be going to fast for this.

Posted by: Bjorn Jonsson Jul 30 2005, 09:35 PM

And in addition to solar conjunction there seems yet again to be a problem with the raw image page at the JPL Cassini site - still no post-conjunction images .

Posted by: volcanopele Aug 1 2005, 07:01 PM

I have posted my Mimas preview on my blog:

http://volcanopele.blogspot.com/2005/08/rev12-mimas-encounter.html

Bjorn, would you mind if I posted a link to your animation, with full credit of course.

Posted by: Bjorn Jonsson Aug 1 2005, 07:45 PM

No problem, by all means do so.

BTW am I correct in assuming that the lack of updates to the JPL raw images page is due to some problem there (not for the first time...) and not due to lack of images from Cassini in the past few days ?

Posted by: djellison Aug 1 2005, 07:47 PM

Solar Conjunction Bjorn

Doug

Posted by: Bjorn Jonsson Aug 1 2005, 07:52 PM

Not any longer - Cassini's solar conjunction period ended 5 days ago.

Posted by: volcanopele Aug 1 2005, 08:04 PM

Yeah, the images are coming back just fine, they are just not on the JPL raw images page, but that may change soon. There are pages for the missing images:

http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=46400

BTW, thanks Bjorn, the animations are great. They are especially useful when there are no official pre-encounter animations (like the official one for Enceladus-2).

Posted by: Sunspot Aug 1 2005, 10:31 PM

Cant believe they haven't fixed the website, it's been broken for months

Posted by: tedstryk Aug 1 2005, 10:49 PM

It is now showing a bunch of broken-link images...usually this means that pictures are coming.

Posted by: Decepticon Aug 1 2005, 11:50 PM

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

Some far off views.

Look at this neat pic of Tethys http://saturn1.jpl.nasa.gov/multimedia/images/raw/casJPGFullS12/N00037360.jpg


Note: Sorry VP I didn't notice the upadte on your blog.

Posted by: tedstryk Aug 2 2005, 12:29 AM

Yep, the first distant views are in....can't wait for the good stuff...here is what we have so far.

Posted by: gndonald Aug 2 2005, 08:24 AM

The Cassini Raw Images page is now showing distant images of Mimas taken on 01/08/2005 from about 840,000km however there has not been an update for about six to seven hours.

I have to agree about the 'invisibility' of the Mimas Flyby, while Mimas may not be a large moon, it does have some of the most visualy dramatic scenery in the area.

After all who can forget either that first Voyager image of Herschel, the http://tinyurl.com/3vfq2 or the http://tinyurl.com/5gp5q taken on February 10th of this year.

Posted by: ljk4-1 Aug 2 2005, 02:03 PM

That's no moon! tm

Posted by: tedstryk Aug 2 2005, 02:40 PM

True

Posted by: Decepticon Aug 2 2005, 03:37 PM

I so nervous! The anticipation is killing me. Looking forward to pic of any stress forces on Mimas.

Also looking forward to Dione images.

Posted by: tedstryk Aug 2 2005, 03:50 PM

Should be interesting. There are a lot of features that could be, but also could be impact related...I am not sure how these line up with Herschel, but the one on the bottom is not aligned with the others.



This image also shows a suspicious feature...

Posted by: volcanopele Aug 2 2005, 04:04 PM

Don't go too crazy searching for new images, they won't show up till around 7pm PDT tonight.

The fractures systems on Mimas seem to be largely explained by impact-generated stresses, particularly stresses generated by Herschel, though this encounter will give us a much better idea as we get much higher resolution images, allowing us to see details in some of the fractures as well as map smaller fracture systems, if they exist.

Posted by: ljk4-1 Aug 2 2005, 04:15 PM

Any tentative atmospheres and/or magnetic fields detected on Mimas or any of the other Saturn moons besides Enceladus or Titan? Are they looking for them with Cassini?

Posted by: volcanopele Aug 2 2005, 04:29 PM

None of the data is back yet. It doesn't playback (or to be more specific, it doesn't show up for us to look at them) until later this evening. In addition, Cassini is too far away from Mimas to detect an atmosphere or magnetic field, even if it were there, which given its very ancient surface, I would very much doubt beyond maybe an atmosphere from sputtering.

Posted by: alan Aug 3 2005, 03:02 AM

New images are up
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS13/N00037626.jpg

Posted by: tedstryk Aug 3 2005, 03:07 AM

Exciting...the imagery of Dione and Rhea is great too. And as for the Mimas imagery, the closest it gets is just under 90,000 km - so it looks like the best is yet to come!

Posted by: Decepticon Aug 3 2005, 03:08 AM

The inner walls of the craters remind me of Phobe's craters.


Oh WOW! Dione... http://saturn1.jpl.nasa.gov/multimedia/images/raw/casJPGFullS13/N00037562.jpg

Rhea! http://saturn1.jpl.nasa.gov/multimedia/images/raw/casJPGFullS13/N00037564.jpg

Posted by: dilo Aug 3 2005, 04:57 AM

A little pseudo-color (UV+G+IR) gallery; on the right the enhanced color versions:
Rhea:http://img91.imageshack.us/my.php?image=rheacolor2e3bq.jpg
Dione (note bluish fractured terrain): http://img91.imageshack.us/my.php?image=dionecolor23za.jpghttp://img91.imageshack.us/my.php?image=dionecolor2e1wx.jpg
Mimas: http://img91.imageshack.us/my.php?image=mimascolor7gt.jpg
Finally, a nice crossed-eye stereogram (different phase angle introduces some shadows issue):
http://img91.imageshack.us/my.php?image=mimasstereo21hf.jpg
(here laser cannon is almost ready to hit Alderan... )

Posted by: malgar Aug 3 2005, 10:10 AM

I've extracted a digital elevation model from the rhea image.
This is the large impact basin rendered in 3D.
The color layer is taken from dilo image.

Posted by: tedstryk Aug 3 2005, 02:50 PM

Some great work, dilo and malgar. Dilo, I have a question about your Cassini color images. How do you compensate for stretching?

Posted by: ljk4-1 Aug 3 2005, 02:59 PM

I don't mean this how it sounds, but the craters appear so sharp that the moon almost looks artificial. Does that make sense?

You sure there can't be some kind of activity on Mimas, even with all the craters?

Posted by: volcanopele Aug 3 2005, 03:05 PM

the sharp craters could be expected given this a fairly low gravity world, though some craters do show some signs of degradation. I'm pretty sure, given the ancient age of the surface, that there isn't present day activity. At least I would be VERY shocked to see any. Maybe a landslide or two, but not cryovolcanism.

Posted by: tedstryk Aug 3 2005, 03:40 PM

I think a major factor too is that when it comes to the saturnian satellites, we are used to looking at underexposed, tiny views that have been greatly stretched and enlarged. The enlargement, plus attempts to reduce noise, made the worlds look smoother than they really are.

This brings to mind a memory. When I was growing up, I enjoyed following the Voyager Neptune encounter. Also, our local library had NASA's Voyages to Saturn and Voyages to Jupiter. Both in the case of the Neptune images, as well as the Jupiter and Saturn images, approach sequences were shown using images enlarged to be the same size...so as the spacecraft approached, the image got sharper rather than larger. I am embarrassed to recall the hours I spent trying to figure out why these worlds looked blurry from far away rather than smaller. I have done similar processing to my Enceladus approach sequence to demonstrate. The above row is a sequence of color images taken as Voyager-2 approached (unfortunately, since various color combinations had to be used, it isn't very even). The lower row shows the same sequence, but resampled to be about the same size. It creates a strange appearance of snapping in to focus. While it is useful for comparison - you can really see Enceladus rotating better than when the different sizes are shown, it looks artifically smooth in the early images.

http://img78.imageshack.us/my.php?image=encapproach3qv.jpg

Also, previews are up!
http://ciclops.org/view_event.php?id=24

Posted by: gndonald Aug 3 2005, 04:32 PM

I'd agree on the cryovulcanism, but the images have bought up some interesting detail on Herschel (see http://tinyurl.com/a96qf), firstly, the 'right' rim of the crater appears to be higher than the left rim and there is also what looks like a landslide in the same region.

The central peak is elongated 'north-south' (where north is the top of the picture) and appears to be flat-topped, there's also what looks like a fresh impact just above the central peak.

I have'nt looked through all the raw images yet, but Cassini does not seem to have imaged the area directly opposite Herschel where the greatest seismic effects would have been felt.

Posted by: dilo Aug 3 2005, 07:38 PM

Yes, in all images I needed to carefully compensate shift between different filters pictures and sometimes I need also to rescale (or even rotate) two of the 3 images in order to match to third one in the best way... however, sometime result still not perfect due to parallax effects (motion of spacecraft+satellite rotation)
It's a patient work, and time is never enough to make all I would like to do!
Bye, Marco.

Posted by: Bill Harris Aug 3 2005, 08:34 PM

(Post#32)

And notice that the interior of Herschel is hummocky, much like the landslide surface noted in the above post. Is it rebound phenomenon, cryovolcanism, or what? We'll know more once we get a closer view of this crater.

--Bill

Posted by: alan Aug 3 2005, 09:36 PM

new batch is up
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS13/N00037712.jpg

Posted by: tedstryk Aug 3 2005, 09:36 PM

http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS13/N00037665.jpg

How cool is Tethys!

http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS13/N00037693.jpg

Mimas near closest approach!

Posted by: alan Aug 3 2005, 09:42 PM

Rings in the background
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS13/N00037682.jpg

Posted by: tedstryk Aug 3 2005, 09:59 PM

Beautiful! Thanks for finding that.

I have put together a global view near closest approach. There are some problems from spacecraft motion, but there is also some other distortion - I can't get it to look round. Perhaps Cassini was just too fast...this might require reprojecting. But this is the best I could do in 10 minutes.

http://img294.imageshack.us/my.php?image=mosaic1ui.jpghttp://img75.imageshack.us/my.php?image=mosaic29ff.jpg

I added another one - this one is a bit better...but there is still distortion.

Posted by: dilo Aug 3 2005, 10:18 PM

Cannot resist!
http://img17.imageshack.us/my.php?image=teti8wz.jpg

Posted by: Sunspot Aug 3 2005, 10:42 PM

Mimas isnt round to start with, so it might not be distortion due to the motion of Cassini. great image by the way.

Posted by: scalbers Aug 3 2005, 10:55 PM

Mimas is a tri-axial ellipsoid - like Enceladus but significantly more out of round. I'm still guessing a bit at the numbers, I had seen some published values of 418x392x382km. Curiously, in doing some limb fitting in the course of making my map, I seem to get a better limb fit by assuming numbers like 398x392x382km. I'll have to see if this holds up when adding in the images from the current flyby.

That's part of the mystery with regards to tidal heating. Why should Mimas have less apparent tidal heating compared with Enceladus, even though it is more out of round with a more elliptical orbit? I've seen a recent paper on-line by J. Wisdom suggesting a spin-orbit resonance in the case of Enceladus.

Posted by: malgar Aug 3 2005, 11:39 PM

Another DTM extrapolation with 3D rendering and an anaglyph of one big crater captured from lastest images of Mimas.

Posted by: volcanopele Aug 3 2005, 11:45 PM

Are these using photoclinometry or are you creating stereo from multiple images?

Posted by: malgar Aug 3 2005, 11:56 PM

photoclinometry! just one input image.
Anaglyph is created from DTM.

Posted by: Bjorn Jonsson Aug 4 2005, 01:05 AM

I'm attaching two images rendered from a quick-and-dirty DTM I did of one of Mimas' craters. They look rather ugly, a major problem is the horizontal stripes in the DTM. They are especially prominent in the second rendering where the illumination is very different from the illumination in the source image. This something which is not nearly as prominent in malgar's DTMs for some reason. Despite this I seem to be using a similar algorithm so I'm not sure why this is.

Posted by: gndonald Aug 4 2005, 02:41 AM

The closest view of the crater appears to be http://tinyurl.com/dapku (62,700km) the sun is coming from the left of the picture.

I can see what you mean about the hummocks in the crater floor and there is also at least one post-impact crater in the floor of Hershel.

Any ideas on how the central peak got so elongated, or what flattened out the peak.

I'm beginning to wonder if we are looking at an 'off-angle' impact.

Last thing, did Cassini image the convergence point for the cracks?

Posted by: tedstryk Aug 4 2005, 03:01 AM

[quote=gndonald,Aug 4 2005, 02:41 AM]
The closest view of the crater appears to be http://tinyurl.com/dapku (62,700km) the sun is coming from the left of the picture.

That image was taken from about 185,000 km. 62,700 was closest approach.

Posted by: volcanopele Aug 4 2005, 03:41 AM

still, that's a nice view of Morgan.

Posted by: malgar Aug 4 2005, 07:32 AM

IMHO we are using exactly the same alghoritm. Horizontal stripes are a big problem not only for you but I use a simple post process on the elevation map. I apply an asymmetric gaussian blur: few pixel in horizontal and more pixel in vertical. I increase them in vertical until stripes disappears. Resolution become lower but is not so essential in DTM. Try with this trick and post your results. Good luck

Posted by: paxdan Aug 4 2005, 08:27 AM

Oh My! wow that is nice

Posted by: Ian R Aug 4 2005, 10:46 AM

Here's a super-res view of Herschel, from a combination of six Cassini images.

Posted by: Ian R Aug 4 2005, 10:52 AM

Another super-res view of Mimas from eariler in the mission. Not the smoothest effort, I know, but it's quite an unusual and interesting view of Herschel.

Posted by: Ian R Aug 4 2005, 11:52 AM

Here's a global super-res view of Mimas.

Posted by: Bjorn Jonsson Aug 4 2005, 11:29 PM

These superresolution images are great and show lots of details.

I tried something similar and the stripes are no longer very prominent. However, lots of details (much of it real) was lost. But the rendering looks nicer (see attached file). To compensate, it would be interesting to try this on a superresolution image of the same crater. Unfortunately most of the images near closest approach are summation mode images (with the exception of the occasional clear filter images) so this is not possible. Probably time to take a fresh look at the stereo code that I didn't finish the last time I worked on it.

Posted by: Decepticon Aug 5 2005, 02:23 AM

Steve Updated the Mimas Map!! Cool Stuff!

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

Posted by: malgar Aug 5 2005, 07:42 PM

I've rendered Herschel crater. Hard work, I had a lot of noise and the "low pass" filter has deleted and distorted a lot of features. I'm not satisfied, but I post it anyway.
The color layer is a "geological" false color posted on ciclops.org.

http://img165.imageshack.us/my.php?image=herschelfalsecolor3d7sr.jpg

Posted by: Bill Harris Aug 5 2005, 10:13 PM

Interesting images.

The impression I'm starting to get is that the hummocky floor of Herschel has the appearance of the the coalescence of multiple slump/landslide features. I wonder if we could be dealing with a caldera instead of an impact feature?

Very odd place.

--Bill

Posted by: volcanopele Aug 5 2005, 11:22 PM

You can get landslides and slump features on craters just as easily as with calderas. Many of Mimas' craters have steep walls so the presence of landslide deposits in a number of craters is not unexpected.

Posted by: Sunspot Aug 8 2005, 03:35 PM

Some new images of Mimas at the CICLOPS website, I don't remember seeing these at the JPL RAW site?

http://ciclops.org/view_event.php?id=24

Posted by: Decepticon Aug 8 2005, 03:38 PM

^ I noticed that myself. Alot of images on CICLOPS web page will not appear on the RAW section of the cassini website.

Posted by: Sunspot Aug 8 2005, 03:42 PM

I couldn't find the one of Mimas against the rings.

Posted by: volcanopele Aug 8 2005, 04:35 PM

Actually, it is there, just poorly stretched:

http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=46853