Juno Perijove 57, December 30, 2023 |
Juno Perijove 57, December 30, 2023 |
Oct 19 2023, 09:08 PM
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
I know the first close Io flyby is still a couple of months away but I'm going to go ahead and start up the topic now with a few preview images that the global map from PJ55 into the pixel scale, lighting conditions, and orientation of the highest resolution images that JunoCam would take (illuminated by the sun, there's always a chance for Jupiter-shine images), based on the current reference spk and c-kernel:
This also assumes an image cadence of 1 every other rotation (so 1 per minute). info about the encounter: CODE Perijove Date (UTC) SC Altitude (Io, km) SC Latitude (Io IAU, deg) SC W Longitude (Io IAU, deg) Vinf (Io, km/s) Phase Angle Magnetic Latitude of Io (Jupiter System III, deg) E Longitude of Io (Jupiter System III, deg) True Anomaly of Io (deg) Separation Angle
PJ57 12/30/2023 08:36:00.681 1500.021 63.694 94.641 30.047 108.885 3.418 228.269 248.805 21.175 -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Jan 1 2024, 05:15 PM
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Senior Member Group: Members Posts: 1643 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Fyi I had applied the noise reduction filter in GIMP with a setting of 12. This may be related to what StargazeinWonder mentions, and would work better if applied to the original image prior to reprojecting onto the cylindrical projection.
-------------------- Steve [ my home page and planetary maps page ]
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Jan 1 2024, 05:58 PM
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#3
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Fyi I had applied the noise reduction filter in GIMP with a setting of 12. This may be related to what StargazeinWonder mentions, and would work better if applied to the original image prior to reprojecting onto the cylindrical projection. I'll look into some post-processing steps today. My first thought was running each mosaic through a median filter in ISIS prior to stacking. EDIT: really not liking the results. The red filter, while noisy, has pretty good detail so I really don't want to smooth that. I suspect that using the noise filter in ISIS would help a lot, but I am not wanting to dive into yet another research topic today after spending all day yesterday trying to wrangle the geometry... -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Jan 1 2024, 09:32 PM
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#4
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Member Group: Members Posts: 234 Joined: 14-January 22 Member No.: 9140 |
To zoom in on the problem, here are magnified patches of one of Jason's images, blue filter only, from the dayside and Jupitershine side, normalized to about the same overall brightness.
Obviously, the difference isn't due to Io itself, but the higher share of noise compared to signal in the darker imagery. Median over a local window (3x3?) is one solution, which of course loses some spatial resolution. We might beat this by combining information from the three color filters, presuming that the peaks and valleys of the speckles will vary from one filter to another and there is usually not sharp color contrast on the same spatial scale as edges in general albedo. So, maybe average the three filters to produce a grayscale image, apply median (2x2?) to that, and then color it with images that apply a larger median (eg, 4x4) to each of the color filters. I've gone down a similar road with some astrophotography images, and there may be more wisdom out there in the community that processes images of deep sky objects (galaxies and nebulae). It's almost an entirely different paradigm than the imagery of planets (dayside), where you can always get all the luminance you want. |
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