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Juno Perijove 24, December 26, 2019
Brian Swift
post Feb 4 2020, 07:07 PM
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AR Quick Look globes for PJ24 (viewable in Safari on devices running iOS 13 or later) at:

Attached Image


PJ24 Flyover animation (4K60FPS) on YouTube at https://youtu.be/3fwycMt2JX4
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post Feb 11 2020, 02:44 PM
Post #32

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This is a partial answer to Björn's question in the PJ 2 and 3 thread.
Has anyone else been flat fielding the JunoCam images and if so, how?

The striping artifacts are most evident in the methane band images. And we have a nice methane band engineering image in PJ24.
During the cruise phase after Earth flyby, I was fairly convinced, that the striping artifacts are mostly an effect of interframe transfer smear and straylight, and studied this extensively.

In order to test for the flat field as a major cause in the less bright Jupiter environment, here an experiment with the mentioned PJ24 image, rendered into a crop of a cylindrical map:
Attached Image

I've run a sequence of an assumed simple familiy of flat fields with one continuous parameter ("codimension 1"). It shows, that one part of the swath shows less striping artifacts for one parameter value, while another part of the swath (but for the same CCD pixel position) shows less artifacts for another parameter value.
I'm considering this as evidence for the hypothesis, that the striping artifacts cannot be removed, at least not completely, by an appropriate constant flat field, but require (additional) modelling of interframe transfer smear and stray light. (I'm aware of the methane band filter characteristics varying with the incidence angle on the CCD. So there remains some residual uncertainty about this conclusion.)
I've been able to model part of the interframe transfer smear and the stray light for EFB images. But I failed to refine the model (within the available time) to a degree that adjustments by those model assumptions introduced less artifacts than we had without those adjustments, meaning that these effects are more complex than I first thought.
I found incidence and emission angle the most significant, but not the only contributors to illumination effects.
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