Juno Perijove 58, February 3, 2024 Options

[StargazeInWonder]

I keep mulling this over and had the following speculation…

Ionization caused solely by electromagnetic radiation normally has a distinct threshold effect. In the way we encounter this most painfully, we can get a sunburn from the UV in sunlight, but interestingly, we cannot get a sunburn from longer or more intense exposure to visible light. (We can get a thermal burn, of course, but that's another phenomenon.) There is an energy of ionization for a given molecule / bond and a photon either reaches that threshold or does not. For the bonds in most organic compounds, it requires UV to reach that threshold. Intense blue light will not give you a sunburn.

What we see with this reddening is directionally aligned with sunburn: It is as though operations during the mission are harming the shortest wavelength filter a significant degree; the next-shortest, less so. This doesn't display the thresholding that one expects with radiative ionization.

Is it possible that the charged particle radiation from Jupiter and the visible light radiation are somehow additive in damaging camera elements, such that the high end of the stochastic distribution of charged particles is enough to cause damage when added to the visible light of different wavelengths, making blue capable of causing somewhat of a sunburn, green less so, and red less still? If so, then is the imagery performed by JunoCam (which is overwhelmingly, of course, of Jupiter) a causative part of the damage? Put another way, might the reddening have been avoided for arbitrary spans of time if the camera had not been used to image Jupiter?

Heaps of speculation there, and too little too late in any case, but the mystery remains intriguing.

[tau]

A further processing of volcanopele's image of Io from post #48.
Colors enhanced using principal components analysis, image enlarged with Upscayl. North is to the left.

[mcaplinger]

It is as though operations during the mission are harming the shortest wavelength filter a significant degree; the next-shortest, less so.

If there has been wavelength-dependent degradation (I don't think the case is 100% made for this, but it would not be unexpected) it is almost certainly due to radiation darkening, which is caused by exposure to the jovian charged-particle environment. https://sci.esa.int/documents/34530/36042/1...rials_Doyle.pdf is a quick introduction to this and other effects in the context of Jupiter missions.

Junocam was designed with rad-hard glass* types in the front half of the lens and normal glasses farther back, shielded by the front half and also by a large cylinder of titanium. Of course, we were only required to last for 8 orbits, so for radiation effects to still be so subtle as to be debatable this late into the mission speaks to the conservatism of our approach. One could have expected the blue channel to be completely gone by this time otherwise.

It's possible that the annealing recovered some glass transmission that might have been lost, since the heater is attached to the optics and the optics thus warmer than the electronics we were trying to fix.

*I often refer to rad-hard glasses, only somewhat humorously, as "pre-darkened" -- they typically have poorer blue transmission on day 1 than their normal equivalents.

[kymani76]

Here's my version of performing upscale and PCA on Jason's image.


Jupitershine image result.

[tau]

Brian Swift's image from post #44 of Jupiter-shine illuminated Io after further processing
- image artifacts removed
- improved alignement of RGB color channels
- color enhancement by principal components analysis (see here and here for a short explanation)
- image noise reduced

[Holder of the Tw...]

Wen JIRAM images?

[mcaplinger]

Wen JIRAM images?

PJ53 JIRAM data was released on 31 Jan 2024, but the cadence seems somewhat variable so it's hard to be certain. Months, certainly, unless there is some result that the team thinks is worthy of a press release.

https://atmos.nmsu.edu/PDS/data/PDS4/juno_j...undle/data_raw/

[volcanopele]

The PDS release calendar is here: https://pds.nasa.gov/datasearch/subscriptio...ndar-2024.shtml

As Mike mentioned, PJ53 (and 51) data was released to the PDS a couple of weeks ago (I'll post my processed versions of that JIRAM data on those pages in a minute). PJ57/58 PDS data (and thus JIRAM data) should be publicly available on the week of September 24. Mike noted that the schedule is a bit variable so that date is approximate though teams seem to be releasing data a few days to a week early. Also they did change up the release cadence a bit... Last year it was 3 orbits every 4 months, and I was prepared for the PDS release at the end of this month (even asked for time off from HiRISE for it...).

[Bjorn Jonsson]

This is an animation showing a simulation of Io's specular highlights:

https://vimeo.com/914591010

The illumination geometry is constant. The flight path is fictional. It is at uniform speed along a straight line from Juno's location in Io-centered coordinates when image PJ57_24 was obtained to Juno's location when image PJ58_26 was obtained and then back to the starting location.

The map of Io used for rendering the animation is a map-projected mosaic of data from images PJ57_24 and PJ58_27. The mosaic does not contain specular reflections. The specular reflections appearing in the animation were added using a preliminary illumination model with the specular highlights based on the Phong illumination model. This gives a relatively good visual match to the specular highlights in the PJ58_26 and PJ58_27 images.

Interestingly, with the current combination of illumination model parameters it was necessary to assume that Mazda is different from the other sources of specular highlights (e.g. Loki), i.e. more reflective and/or shiny. Without this assumption Mazda was too dark in this simulation. It is probably possible to use a different combination of model parameters where this assumption is not necessary or to use a more sophisticated specular reflection model (the Phong specular reflection model is a very simple empirical model). Interestingly, Mazda is *not* brighter than Loki Patera in the Galileo I32 image showing specular highlights from Loki etc.