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Juno Perijove 47
Bjorn Jonsson
post Jan 8 2023, 04:04 PM
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QUOTE (volcanopele @ Jan 7 2023, 04:54 PM) *
Honestly, not seeing a lot of evidence for surface changes, but they would have to be pretty large scale to be seen. We are facing two issues. One: the phase angle is pretty high in these images and so you canít just use a base map to compare to, you also need to look at New Horizons, Galileo, or even Voyager images with similar phase angles. Ioís surface materials have weird phase functions. For example, Colchis Regio is darker at higher phase angles.

True, these changes with phase angle greatly complicate the search for surface changes (as also mentioned at the end of my earlier post). I noticed that this was also a big problem in the Europa images when looking for possible surface changes (a long shot, a very long shot) in Juno's recent Europa images.

This reminded me of an old animation I did of Io's photometric behavior. See this thread which has some details, including where I found detailed information on how the color and brightness of different parts of Io's surface brightness change as a function of phase angle. I decided to do a slightly improved version of this animation. It can be found at Vimeo:

https://vimeo.com/787330491
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Brian Swift
post Jan 10 2023, 07:05 AM
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Prominent structure appearing in PJ47_89 and PJ47_91 rended as a cross-eye stereoscopic pair.
Both images are rendered from position of PJ43_90 using orthographic projection.
The 3D effect is more pronounced when zoomed in to smaller regions of image.
Full size image at https://www.missionjuno.swri.edu/junocam/processing?id=14640
Attached Image
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Brian Swift
post Jan 10 2023, 07:16 AM
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Prominent structure appearing in PJ47_89, PJ47_90 and PJ47_91 rended as a short back/forth animated sequence.
Movement due to both perspective change and cloud motion visible.
If someone wants to do the math, I expect they can calculate the height of high altitude cloud near top (assuming it isn't moving too much over 5 minute span of images)

Larger resolution version at https://www.missionjuno.swri.edu/junocam/processing?id=14641

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Bjorn Jonsson
post Jan 18 2023, 11:08 PM
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This is image PJ47_90 in approximately true color/contrast and enhanced versions:

Attached Image
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The color accuracy in the dimly lit areas is almost certainly significantly lower than in brighter areas farther from the terminator and/or closer to the equator.

BTW I noticed that some of the PJ47 southern hemisphere images are extremely noisy. My software automatically removes spikes but doesn't do it very aggressively. I used to consider images where the software removed ~5000 spikes as very noisy but for image PJ47_113, about 25,000 spikes were removed. I am fairly sure that this is (by far) the largest number I have seen. I have been experimenting with processing the raw images in Photoshop *before* running them through my regular processing pipeline. This seems to help. Filter -> Dust & Scratches seems to work well whereas Filter -> Median is too aggressive for my taste (the raw image becomes too smooth and even 'contoured').

The images continue getting redder. I now multiply blue with >4 relative to red. For comparison, for the early orbits I was using a value close to 2.5.
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mcaplinger
post Jan 19 2023, 09:19 PM
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Added to https://www.nasa.gov/feature/jpl/juno-space...lyby-of-jupiter

QUOTE
UPDATED Jan. 19, 2023: Data received from Juno indicates the first four of 90 images taken by the spacecraftís JunoCam outreach camera during its most recent flyby of Jupiter (Perijove 47) were degraded: two were unusable and two had a high level of image noise. The JunoCam team believes the loss of these images is due to an anomalous temperature rise that occurred when the camera power was turned on in preparation for the flyby. Subsequent images Ė captured after the instrument returned to normal temperatures Ė were not degraded. The team plans to leave the instrument turned on after the next flyby, Perijove 48, rather than powering it off and then on again before Perijove 49.

JunoCam is a color, visible-light camera designed to capture pictures of Jupiterís cloud tops. It was included on the spacecraft specifically for purposes of public engagement; although its images have been helpful to the science team, it is not considered one of the missionís science instruments. The camera was originally designed to operate in Jupiterís high-energy particle environment for at least seven orbits but has survived far longer. The spacecraft will make its 48th pass of the planet on Jan. 22.


I can't comment on this further except to say that this was not my suggested wording.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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vjkane
post Jan 20 2023, 12:45 AM
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QUOTE (mcaplinger @ Jan 19 2023, 01:19 PM) *
Added to https://www.nasa.gov/feature/jpl/juno-space...lyby-of-jupiter



I can't comment on this further except to say that this was not my suggested wording.

Anyone know how many more perijoves before the Io encounters next year?


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mcaplinger
post Jan 20 2023, 07:04 AM
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QUOTE (vjkane @ Jan 19 2023, 04:45 PM) *
Anyone know how many more perijoves before the Io encounters next year?

The close Io approaches are on PJ57 (2023-12-30) and PJ58 (2024-02-03).


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volcanopele
post Jan 20 2023, 03:45 PM
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There are passes on 49, 51, 53, and 55 before the close encounters, each of these at closer and closer distances.

There is a table of encounters here:

https://en.wikipedia.org/wiki/Exploration_o...Juno_spacecraft


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Bjorn Jonsson
post Jan 21 2023, 02:58 AM
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Image PJ47_113 in approximately true color/contrast and enhanced versions. Oval BA is prominent. North is up.

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Bjorn Jonsson
post Apr 3 2023, 10:33 PM
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QUOTE (Brian Swift @ Jan 10 2023, 07:16 AM) *
Prominent structure appearing in PJ47_89, PJ47_90 and PJ47_91 rended as a short back/forth animated sequence.
Movement due to both perspective change and cloud motion visible.
If someone wants to do the math, I expect they can calculate the height of high altitude cloud near top (assuming it isn't moving too much over 5 minute span of images)

Larger resolution version at https://www.missionjuno.swri.edu/junocam/processing?id=14641

Attached Image

Some time ago I decided to try determining these cloud altitudes using stereo. I have not been able to generate useful DEMs of Jupiter from stereo images (the resulting DEMs have been extremely noisy) but I have had some success with a few isolated points since in that case I can select points near clearly defined features. The result is the image below showing cloud altitudes in km relative to the 1 bar level at several locations. I used images PJ47_90 and PJ47_91 to compute the the altitude values. There are lots of uncertainties and I don't think these values are very accurate. But at least they seem to make some sense since dark clouds are always at a lower altitude than nearby, bright clouds. Bright clouds are known to usually be at a higher altitude than dark clouds so this was the expected result.

Attached Image


This is methane filter image PJ47_92 rendered with the same viewing geometry as above:

Attached Image


A similar pattern appears, i.e. the numbers indicate that bright features are generally higher in the atmosphere but the image is very noisy.
And a smaller image with a latitude/longitude grid to show the viewing geometry:

Attached Image


There are additional details in the Think Tank section at the missionjuno website, including crude back-of-the-envelope error estimates, i.e. possible effects of cloud motions in the 2 minutes between images PJ47_90 and 91.
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