Juno Perijove 22, September 12, 2019 |
Juno Perijove 22, September 12, 2019 |
Sep 13 2019, 12:37 AM
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#1
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Senior Member Group: Members Posts: 2504 Joined: 13-September 05 Member No.: 497 |
Images have started appearing on missionjuno.
-------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Sep 13 2019, 03:55 AM
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#2
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Member Group: Members Posts: 137 Joined: 22-July 14 Member No.: 7220 |
Thanks for letting us know!
First composite image using the PJ22 data JNCE_2019255_22C00017_V01 JNCE_2019255_22C00018_V01 JNCE_2019255_22C00019_V01 JNCE_2019255_22C00020_V01 JNCE_2019255_22C00021_V01 JNCE_2019255_22C00022_V01 Reprojected to the perspective of '22. Jupiter - Fisheye Composite - Perijove 22 |
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Sep 13 2019, 11:41 PM
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#3
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Member Group: Members Posts: 137 Joined: 22-July 14 Member No.: 7220 |
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Sep 14 2019, 01:13 AM
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Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
Spectacular - very cool how the projection from close up makes Io's shadow look crazy big.
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Sep 14 2019, 01:27 AM
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Senior Member Group: Members Posts: 2073 Joined: 13-February 10 From: Ontario Member No.: 5221 |
Reminds me of a classic science fiction movie involving Jupiter...
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Sep 14 2019, 03:21 PM
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#6
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IMG to PNG GOD Group: Moderator Posts: 2250 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
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Sep 14 2019, 06:28 PM
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#7
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Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
Stunning, Bjorn. I always appreciate the attempt at true colour.
I suppose you've done some masking of the sky - the pixel values are zero in the sky, but small though nonzero in the shadow, as a gamma-tweak illustrates: Is that just a nonzero black level in the shadow? Another idea would be real scattered illumination from the illuminated atmosphere outside the shadow, or illumination from partially sunlit moons (other than Io). Both those seem unlikely. |
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Sep 14 2019, 07:52 PM
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#8
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Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
A related point: knowing the geometry we should be able to plot the edge of the umbra on the image, and then measure how much scattered light is visible inside the umbra - perhaps interesting from the atmospheric science point of view?
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Sep 14 2019, 08:55 PM
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#9
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Senior Member Group: Members Posts: 2504 Joined: 13-September 05 Member No.: 497 |
Is that just a nonzero black level in the shadow? I don't see any signal in the shadow in the raw images that is any brighter than the stray light from the instrument. Stay tuned, the later images show the shadow even better. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Sep 14 2019, 11:58 PM
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#10
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Member Group: Members Posts: 137 Joined: 22-July 14 Member No.: 7220 |
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Sep 15 2019, 05:22 AM
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#11
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
for those fallowing this using Celestia , there is a spice ssc file on Celestialmatters http://forum.celestialmatters.org/viewtopi...start=15#p15441 and some screen shots http://forum.celestialmatters.org/viewtopi...start=15#p15437 |
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Sep 15 2019, 08:03 AM
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#12
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
I have distorted the image to circularize the shadow, and I don't see any obvious Io plumes, but then the noise of Jupiter's variation makes that a difficult search.
If there is any discernible movement of Io's shadow while ≥2 images were made of it, then it would be possible to divide an image of its penumbra by the same area of Jupiter in sunlight and search for relatively faint plume shadows. |
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Sep 16 2019, 10:53 PM
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#13
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IMG to PNG GOD Group: Moderator Posts: 2250 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Stunning, Bjorn. I always appreciate the attempt at true colour. I suppose you've done some masking of the sky - the pixel values are zero in the sky, but small though nonzero in the shadow, as a gamma-tweak illustrates: Yes, I did some feathered masking in Photoshop near the limb. Otherwise I'd get a sharp, unrealistic cutoff in the dark (but not totally black) area a bit outside of Jupiter's limb. This is because I reprojected the raw framelets to simple cylindrical projection and added 200 km to Jupiter's radius when reprojecting to avoid losing Jupiter's sky (which usually happens if I use the cloudtop radius value). A related point: knowing the geometry we should be able to plot the edge of the umbra on the image, and then measure how much scattered light is visible inside the umbra - perhaps interesting from the atmospheric science point of view? This would be difficult because the shadow contains stray light from the instrument as pointed out in an earlier post. This scattered light varies in non-trivial fashion depending on the viewing geometry, the sun direction etc. I haven't attempted to model these effects and correct for them. However, if memory serves there are some Galileo images where a big satellite shadow is visible. These images might have less stray light and/or be easier to calibrate if measurements of the umbra brightness are desired - I suspect compression artifacts in the Galileo images might make this impossible to measure properly though. |
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Sep 16 2019, 11:17 PM
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#14
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IMG to PNG GOD Group: Moderator Posts: 2250 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
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Sep 17 2019, 03:05 AM
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#15
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
HST images might have less of a stray light issue than Juno or Galileo, and resolve the moon shadows fairly well?
https://hubblesite.org/contents/news-releas...ws-2015-05.html In all cases, I guess an operational constraint in measuring the brightness inside an umbra would be image depth. If you're calibrated to show the surface of Jupiter, I would guess that the brightness in the center of a moon shadow would be far below the quantum of sensitivity. Eg, JunoCam images are returned at 8 bits, so < 1/256 is essentially zero? FWIW, when Io, Europa, or Ganymede is casting a shadow on Jupiter, the other two of that trio must either be on the far side of Jupiter or present as a razor-thin crescent. Callisto, however, is potentially a spoiler, and a crescent/gibbous Callisto could potentially be shining onto the scene. |
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