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Cassini Images Of The Galileans
ugordan
post Dec 9 2005, 05:25 PM
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Has anyone out there experimented with processing the very limited image dataset of Jupiter's icy moons? Most images I found that targeted them specifically are horribly underexposed to the point they look like 4 bit images.
I tried fiddling around with what can be done, below's my poor attempt at color compositing Europa, Ganymede and Callisto images. I took 3 polarized UV and GRN filtered images and stacked them together to reduce noise. I also stacked various IR images except for Europa where only a single red frame existed and, consequently, the red channel is very noisy.
Oh, and then there's the *awful* 2Hz banding problem. It's quite noticeable, even in stacked images. I don't know how to remove it as it's at the point of being random brighter pixels (severe underexposure) rather than a brightness gradient...

Here's what I came up, the images are magnified 3x:

Attached Image


BTW, I was wondering whether we could open a dedicated thread to posting Cassini processed images from the PDS (be them Jupiter or Saturn ones), there's really a *lot* of material that could provide.. well, very pretty images if nothing else biggrin.gif
Sort of like that "processing of the historical imagery" thread...

Does that sound like a bad idea, is anyone interested?


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tedstryk
post Dec 9 2005, 09:41 PM
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QUOTE (ugordan @ Dec 9 2005, 05:25 PM)
Has anyone out there experimented with processing the very limited image dataset of Jupiter's icy moons? Most images I found that targeted them specifically are horribly underexposed to the point they look like 4 bit images.
I tried fiddling around with what can be done, below's my poor attempt at color compositing Europa, Ganymede and Callisto images. I took 3 polarized UV and GRN filtered images and stacked them together to reduce noise. I also stacked various IR images except for Europa where only a single red frame existed and, consequently, the red channel is very noisy.
Oh, and then there's the *awful* 2Hz banding problem. It's quite noticeable, even in stacked images. I don't know how to remove it as it's at the point of being random brighter pixels (severe underexposure) rather than a brightness gradient...

Here's what I came up, the images are magnified 3x:

Attached Image


BTW, I was wondering whether we could open a dedicated thread to posting Cassini processed images from the PDS (be them Jupiter or Saturn ones), there's really a *lot* of material that could provide.. well, very pretty images if nothing else  biggrin.gif
Sort of like that "processing of the historical imagery" thread...

Does that sound like a bad idea, is anyone interested?
*


Great work on those images!
It does sound good. I eagerly awaited the release of the data, and was very dissapointed. Part of the problem is that many of the best observations would have been during the period in which an anomaly forced the spacecraft into safe mode.


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ugordan
post Dec 9 2005, 11:43 PM
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QUOTE (tedstryk @ Dec 9 2005, 10:41 PM)
Part  of the problem is that many of the best observations would have been during the period in which an anomaly forced the spacecraft into safe mode.
*

I never dug around enough to find specific details about the reaction wheel anomaly, is one of the wheels permamenently shut-down and the backup is now being used? How long exactly was the spacecraft "out"? Since the flyby was so distant there was no great distance change around C/A so apart from lost observations I'd imagine there were no good close-up opportunities anyway?

While I'm at it, here's a weird image I just dug out of PDS. It's actually two WAC clear frames with 68 second exposures that seem to target a nebula of some sort. I'm compelled to say Trifid nebula, but it really doesn't look like it, apart from the dust lanes also splitting it in three. The images are W1463108513_1.IMG and W1463134433_1.IMG, taken in May 2004.
A bit from the LBL file :
METHOD_DESC = "ISSPT2.4.1;STAR:TYPE=K,MAG=10.0000;ISS_C44ST_STARCALEC001_CIRS_2"


Attached Image


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um3k
post Dec 10 2005, 03:29 AM
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http://www.seds.org/messier/xtra/ngc/n3372.html
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tasp
post Dec 10 2005, 03:48 AM
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If you have a CRT monitor (may not work on LCD due to black level quirk of that technology) turn the brightness all the way up.

That photo has a great deal of faint nebulosity in it. A better astronomer than I will probably reconize it instantly.
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tedstryk
post Dec 10 2005, 05:50 AM
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QUOTE (ugordan @ Dec 9 2005, 11:43 PM)
I never dug around enough to find specific details about the reaction wheel anomaly, is one of the wheels permamenently shut-down and the backup is now being used? How long exactly was the spacecraft "out"? Since the flyby was so distant there was no great distance change around C/A so apart from lost observations I'd imagine there were no  good close-up opportunities anyway?

While I'm at it, here's a weird image I just dug out of PDS. It's actually two WAC clear frames with 68 second exposures that seem to target a nebula of some sort. I'm compelled to say Trifid nebula, but it really doesn't look like it, apart from the dust lanes also splitting it in three. The images are W1463108513_1.IMG and W1463134433_1.IMG, taken in May 2004.
A bit from the LBL file :
METHOD_DESC = "ISSPT2.4.1;STAR:TYPE=K,MAG=10.0000;ISS_C44ST_STARCALEC001_CIRS_2"


Attached Image

*


That is a neat image! If memory serves me correctly, it was out for about 10 days, recovering just before closest approach. But most of the full phase multispectral data was lost by then.


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SigurRosFan
post Dec 10 2005, 01:47 PM
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It is the great Carina Nebula (NGC 3372) with Keyhole Nebula (NGC 3324) and eta Carinae. Amazing!


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The Messenger
post Dec 10 2005, 04:33 PM
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QUOTE (ugordan @ Dec 9 2005, 04:43 PM)
I never dug around enough to find specific details about the reaction wheel anomaly, is one of the wheels permamenently shut-down and the backup is now being used? How long exactly was the spacecraft "out"?

According to the Cassini event log, Reaction wheels on Cassini have experienced power related failures about twice yearly. They have always been able to 'reset the breakers', but if the fault occurs during a critical operaton it can trigger safe moding. The faults are thought to be caused by cosmic rays.
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ugordan
post Dec 10 2005, 04:55 PM
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QUOTE (The Messenger @ Dec 10 2005, 05:33 PM)
According to the Cassini event log, Reaction wheels on Cassini have experienced power related failures about twice yearly. They have always been able to 'reset the breakers', but if the fault occurs during a critical operaton it can trigger safe moding. The faults are thought to be caused by cosmic rays.
*

I'm not sure we're talking about a power anomaly here. IIRC, the problem was mechanical and they stopped using that wheel. The vibrations might have even damaged one of the instruments (MIMI ?).


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Guest_BruceMoomaw_*
post Dec 10 2005, 10:31 PM
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One wheel did indeed develop problems serious enough to stop using it during the Jupiter flyby (interrupting about a week of their observations) -- but the others continue to work well mechanically. (I have some more information on this tucked away somewhere in an E-mail from Robert Mitchell, if I can find it.)
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The Messenger
post Dec 11 2005, 03:16 PM
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QUOTE (BruceMoomaw @ Dec 10 2005, 03:31 PM)
One wheel did indeed develop problems serious enough to stop using it during the Jupiter flyby (interrupting about a week of their observations) -- but the others continue to work well mechanically.  (I have some more information on this tucked away somewhere in an E-mail from Robert Mitchell, if I can find it.)
*

They tentatively identified the problem (after consulting with the manufacture), as a lack of lubrication. They changed the rotational duty cycles, and the problem went away. The event logs are unclear as to whether they suspended use of the fourth wheel, but they seem to imply they are all functioning normally.
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SigurRosFan
post Dec 23 2005, 12:48 PM
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Here is the processed Carina Nebula:

PIA07773: Cassini's Galactic Aspirations - http://photojournal.jpl.nasa.gov/catalog/PIA07773

Cassinis Carina Nebula:


--- Cassini briefly turned its gaze from Saturn and its rings and moons to marvel at the Carina Nebula, a brilliant region 8,000 light years from our solar system and more than 200 light years across. Nearly every point of light in this image is a star in our galaxy, the Milky Way.

The nebula is a region of gas and dust made to glow by the ultraviolet light bursting from bright, hot and extremely massive young stars within. Darker regions in the scene are not devoid of stars; rather, they are areas where dense clouds of dust block the light from background stars.

This image and others like it are taken by the spacecraft from time to time for calibration purposes. Calibration images rarely contain such incredible sights. This one affirms Cassini's position as the farthest, working astronomical observatory ever established around our sun -- our eyes on the cosmos, a billion miles from Earth.

The image was taken using the Cassini wide-angle camera on May 14, 2005. The view is a 68-second, clear-filter exposure. ---


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ugordan
post Dec 23 2005, 12:59 PM
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I'm wondering if the "sudden" public release of this pic has anything to do with it being dug up here first a while ago? wink.gif
After all, it was taken over a year and a half ago, maybe we reminded someone out there the pic (two, actually) existed in the first place cool.gif

EDIT: Unless they took another set in May this year, I think they're mistaken on the year - it was 2004 not 2005, the former images are already on the PDS, which is where I got them.


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