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Processing VIMS cubes, An attempt at "true" color
tedstryk
post Sep 22 2006, 09:12 PM
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For Jupiter and Saturn, I am biased toward the right hand images based on experiences with a telescope, but this brings in a whole new host of visual issues...


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ugordan
post Sep 25 2006, 08:02 PM
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I've been experimenting with cleaning up the VIMS visual channel a bit. I've found a cube that captures the night side of Titan with the entire 64x64 hires field of view that served as an augmented dark background to remove the pesky noise. It turned out better than I hoped. Unfortunately, the noise doesn't seem to be as static as I thought. Most of the noise is removed, but some isn't.

To illustrate just what mess the VIMS cubes are (including their calibration data), here are a couple of before and after images:



The bottom image is one of the highest resolution views of Iapetus by VIMS. The noise is disastrous. You can actually see it's mostly coincident with the ring image above.
My dark current removal model assumes noise is linear with exposure, this seems to work well. The background will need some touching up still.

I emailed one of the guys responsible for the PDS volumes, he said he'll look into it and get back to me. We shall see, though I'm not getting my hopes up.


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ugordan
post Sep 26 2006, 07:33 AM
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Sure enough, I got a response from the VIMS team. They had this to say:

QUOTE
New dark models have not been generated with regularity and users of the VIS science data have been doing corrections after the calibration pipeline by looking at average values along columns in data and using these values to correct their data.

That doesn't sound like a very exact science, though.


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edstrick
post Sep 26 2006, 09:49 AM
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It probably boils down to too-much-to-do, not-enough-techies, not-enough-grad-students...

The sort of thing that pennypinching does to a live mission. They'll have time for a systematic beginning-to-end calibration effort when the mission is over.
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ugordan
post Sep 26 2006, 02:27 PM
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To reiterate what you said, on my asking if updated calibration data will be provided, he said that will happen at the end of Cassini mission. An earlier update may be possible, but not likely.

Guess that means I'm stuck with homebrewn dark current models <sigh>...


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ugordan
post Oct 4 2006, 05:55 PM
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Here are a few quick results from the new PDS release. Not that much interesting stuff in there this time. These don't have the sRGB correct gamma of 2.2 because it just looks too washed out to me and it really brings the nasty vertical noise out. I chose a gamma of 1.33 instead. Magnified 2x.

The first image is coincident with an ISS wide-angle shot. The 3rd image from the left shows the F ring, the 4th shows Titan's north pole at high phase. The Saturn mosaic has one of the moons visible at the bottom - might be Dione/Tethys/Rhea, I haven't checked. The last image was taken during that Titan flyby where we had Saturn emerging from behind Titan's limb. You can barely see part of Saturn's crescent there, too bad the view didn't capture more of it.


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Indian3000
post Oct 11 2006, 11:53 AM
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First test to process VIMS cube ( gamma 2.2 )


v1509053994_1

color
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thumbnails
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v1509133941_1

color
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thumbnails
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v1509134411_1

color

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thumbnails
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and a small screenshot of my software ( perharp a release un some days .. or weeks smile.gif )

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elakdawalla
post Feb 18 2011, 10:20 PM
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Hey folks, the Rings Node has generated preview images for Cassini VIMS cubes to their OPUS search tool. The attached screen cap shows what these look like for a colorful object, Iapetus. Here's an explanation by Mark Showalter of what the preview images show. This will make it much easier to browse for good VIMS data!
Attached thumbnail(s)
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ngunn
post Apr 28 2011, 09:27 PM
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A superb piece of work at TPS but we have to have it here too.

http://www.planetary.org/image/2383059379_c56b0272cb_o.png

Believable true colour is a great gift. Thank you Gordan.
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