Enceladus PDS image products Options

[Bjorn Jonsson]

Following discussions in the Image Processing Techniques subforum (see in particular this thread but also this one) I have now managed to create DEMs of acceptable quality of Enceladus using shape from shading and extensive post processing (mainly destriping). I now have a DEM mosaicked together from 5 images obtained during Cassini's first flyby of Enceladus in 2005. This will eventually become a global 23040x11520 pixel DEM but finishing it is going to be a lot of work (I will probably be using 50-100 images or more). Not all of Enceladus has been imaged at this resolution but there are many high resolution patches and I want a DEM big enough for these.

This 5 image DEM was big enough for me to really want to see what an Enceladus DEM animation would look like. So here we go:

 enceladus_sfs_umsf.avi ( 7.74MB ) Number of downloads: 1196


The field of view is 50 degrees. Most of the animation is at an altitude of 25-30 km. This is similar to Cassini's altitide during the closest flybys and the speed is not far from Cassini's speed either. However, the animation starts and ends at higher altitudes and we also swoop down to an altitude of ~10 km where the resolution of the DEM is highest.

This is the Cassini image I used for the highest resolution part of the DEM:



And a single frame from the animation showing a part of this terrain:



The DEM should be fairly accurate - in particular the animation should give a very good general idea of what Enceladus looks like even though some details are inaccurate. Also a higher resolution DEM is really needed for these low altitudes - the surface should look less smooth than it does here. Most of the striping is real though as there are lots of parallel ridges and grooves on Enceladus. There may be some spurious stripes but these are very subtle - the obvious ones are real.

I'll do a new animation once I have a significantly bigger DEM. It will probably have better optimized illumination. Shadows are really needed in the first half of this one because I optimized the illumination for the highest resolution part of the DEM. We fly over that part of the DEM at roughly 00:30.

EDIT: To play the animation you need to have an H.264 codec installed (if you are using Windows you can find one here for example).

[volcanopele]

Not bad, not bad at all. You did better at blending the high res frame in with the rest than I did:

http://www.ciclops.org/view/2456/Enceladus...ling_Hemisphere

[Ian R]

That's top-drawer, Bjorn. Simply top-drawer.

[machi]

Feast for the Eyes!

[tedstryk]

Wow...Bjorn, that is all I can say, wow. Great work!

[ElkGroveDan]

Bjorn knows more than a little bit about ice.

[Bjorn Jonsson]

Bjorn knows more than a little bit about ice.

Yes, a bit .

Regarding Enceladus, more mosaics are coming in the next several weeks, possibly better than this one. And the DEM I now have of most of the terrain visible in the mosaic I posted turned out awesome - I even managed to confuse a rendered image with a Cassini image for a few seconds, the first time this has happened to me. Needless to say I was happy.

BTW ISIS is turning out to be easier to use than I had expected. I used ISIS 2 a bit several years ago but ISIS 3 (which I'm using now) is considerably easier to use in my opinion.

[elakdawalla]

Are you using ISIS on a Mac or running Linux?

[Bjorn Jonsson]

Are you using ISIS on a Mac or running Linux?

Linux on a machine with a dual boot configuration (Windows 7 and Linux).

[djellison]

On a Mac, apart from having to use the terminal to set some path variables before you use it - it's actually fairly easy. You can run it all from the terminal ( Mac version of a dos prompt ) or you can have actual programs for each app in turn.

[ugordan]

Calibrated NAC RGB view of Enceladus from Nov 30, 2010:

[machi]

Beautiful!

[Phil Stooke]

agreed!

Phil

[ngunn]

An all time classic. That deserves wide circulation.

[ugordan]

Thanks.

BTW, if that image looks slightly "foggy" to you, it's not an imaging artifact, it's the dense bulk of E ring around the moon revealing its presence. If Enceladus happened to split the ring optical density along Cassini's line of sight precisely in half, you would expect the background beyond Enceladus' dark limb to be twice as bright as the foreground. Here it's not quite that, but reasonably close. A rough measurement shows the foreground portion at about 60-ish percent brightness of the background.

[Stu]

Absolutely beautiful. Seriously, why your images aren't *everywhere* - in books and magazines, and on NASA's own websites - is a mystery to me.