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Juno perijove 7: GRS images, July 11, 2017
Gerald
post Jul 19 2017, 01:02 PM
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This article of John Rogers (BAA) contains an animated GIF derived from the four close-up PJ07 GRS images. The images of the GIF are reprojected from the raws to the same position on the spacecraft trajectory, and manually corrected for most of the residual geometrical inaccuracies.
It shows a global acyclonic rotation of the GRS. Extracting residual parallax for 3D images in an unambiguous way is pretty hard, and I'm unaware of any successful attempt. Using these images as L/R images of an anaglyph would visualize true motion of features between images as a 3D impression. Being aware of this effect could help to identify subtle differential motion within the GRS.
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Sean
post Jul 30 2017, 02:30 PM
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Here is my take on the GRS sequence using Gerald's work...



Upscaled, processed & cropped.


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nogal
post Jul 30 2017, 05:09 PM
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QUOTE (Gerald @ Jul 19 2017, 02:02 PM) *
This article of John Rogers (BAA) contains an animated GIF


Am I seing two moons (images 2 and 3) crossing from left to right?
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Gerald
post Jul 30 2017, 10:51 PM
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That's most likely energetic particle hits. Most repetitive camera artifacts are filtered out. Lighnings are possible, but unlikely. Moons would probably look differently, less sharp, and probably moving diagonally due to the rapidly changing perspective. They would probably be displaced between camera color filters, showing up as three dots in a row in different colors within one image. Note, that we are rather close to Jupiter during the flyby, just a fraction of the Roche limit. Moons that close to Jupiter would be very unusual, however not entirely impossible.
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nogal
post Jul 31 2017, 05:03 PM
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Many thanks for your information-packed reply, Gerald.
I went searching for the Roche limit and the Wikipedia article added a lot to what I remembered. If I understood correctly, the limit for a rigid body is about 900km (PJ7 was at 3500km). Anyway WIBN if those were moons ar a broken comet/asteroid taking a final plunge...
Cheers
Fernando
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Gerald
post Jul 31 2017, 09:50 PM
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The Roche limit for a rigid spherical body is about 1.26 times the radius of the primary body, multiplied by a factor derived from the density quotient. With Jupiter's radius of about 70,000 km, we get a Roche limit of 70,000 km x 0.26 = 18,000 km altitude. This applies to rigid bodies of a density of about 1.3 g/cm³ like Jupiter's mean density. An iron asteroid could probably plunge into Jupiter's atmosphere without prior break-up due to its high density compared to Jupiter.
The images of the GRS have been taken from altitudes between 6200 km (#59), and 16,500 km (#62).
Small bodies of sufficient shear and tensile strength may survive well within their formal Roche limit, too.
Impacts of small bodies into Jupiter's atmosphere have been observed. Hence unlikely, but not ruled out to observe such an event.
The latest such observed impacts have been observed in March 2016, and in May 2017.
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nogal
post Jul 31 2017, 10:14 PM
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Thanks again Gerald.
The article was the one you point out but I misunderstood the tables... Oh well, back to the homework ohmy.gif sad.gif
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Sean
post Aug 1 2017, 12:03 AM
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I had another stab at Gerald's PJ07_062...


Here are some 4k images cropped from the portrait...








Upscaled, processed & extended




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Gerald
post Aug 2 2017, 10:52 PM
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Here the result of some recreation with PJ07, #053:
Attached Image

It shows Jupiters NN-LRS-1, NN for north-north, LRS for "Little Red Spot". This version is reprojected to about one and a half minutes after the original image time, in order to bring the storm closer to nadir. Then, I've enhanced the image with a sequence of several methods, first an automated heuristics which adjusts for some of the illumination and light scattering effects followed by gamma stretch to the 4th power of radiometric values, then some arbitrary white-balancing, non-linear brightness-stretch, some saturation enhancement, sharpening, point-noise filtering, masking to a disc.
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