(Started a new thread to avoid cluttering up the PJ57 thread with PJ58 discussion.)
I guess to put this imagery to a rubber-meets-the-road standard, the question of how much Io is changing over the cadence of 1979-2024 (and into the future at a similar timescale) is a key parameter. If at some level of regional imagery we see a change occur and this is our one opportunity to do pin that down chronologically, that's distinctive value. If at some level of resolution Io is probably pretty much the same in 2045 as in 1979, then any image is as good as any other, and then maybe the jupitershine imagery adds little. And I'm making it sound like the change is a known quantity, but it's much more complex than that, with stochastic nature and unknowns pertaining to Io, to future missions, to its activity, all challenging and exciting. However it shakes out, hats off to those of you playing a part. People who haven't been born yet will study these images and potentially (this is partly up to Io itself) advance the science with them.
FWIW, the massive ground based telescopes now in the works will provide the potential for regular monitoring of Io's visible changes, subject to geometry, and observational time. Just a pinch of observation time, though, would easily surpass the scarcity of spacecraft missions we have had so far.
From the PJ57 thread:
I expect to see some beautiful images of Ra patera, my favorite volcano. Located near the terminator, we should finally have an idea of the topography of this shield volcano. And then, we'll have some incredible views of Loki. I wonder about the topography of this lava lake and especially its surroundings, which looked quite flat in one of Galileo's last images. Fingers crossed.
My initial cut at PJ58 image timing for Io is:
2024-034T17:32:00, two images, high and low TDI, RGB
2024-034T17:39:00, two images, high and low TDI, RGB
2024-034T17:50:00, four images, first high TDI, three low TDI, RGB
2024-034T17:56:00, two images, high and low TDI, RGB
high TDI will be 6, low TDI will be 2.
All image spacing is 60 second. All compression is lossless. I thought about taking one-band images but due to various constraints I couldn't make it work without compromises.
Feel free to provide feedback. But keep in mind that the FOV of Junocam rapidly slides across Io near closest approach, so if I did something that seems odd, I might have done it intentionally.
A pretty decent set of observations. I might replace the second set with an extra image at the front of the third set (so roughly 2024-034T17:49:00), but I'm not sure how that works for you for bandwidth and data volume. The second set doesn't really add much to the coverage or resolution, and wouldn't be useful for something like the Masubi plume. With high TDI at 2024-034T17:49:00, should provide highest resolution coverage of Io. Covers Masubi, Kanehekili, Shamshu, and Janus. or just take the High TDI image in the second set? The main "Kodak moment" is in the first set anyway.
for 17:49 this is what I get:
I presumed that if the third block of four gets shifted forward a minute, so starting at 17:49 instead of 17:50, the fourth block could also be moved up a minute.
17:49:30 still has Masubi in the FOV but it is much closer to the limb. Still a better view than 17:50:00. and it has the benefit of having a higher resolution view of East Kanehekili (second highest priority "new volcano" target IMHO at Io from JIRAM data after Tonatiuh) that at least with the current predicts we would miss at 17:49. We would lose the best full-color dayside opportunity.... but there would still be two opportunities. I still think that 17:50 is preferable to 17:49:30 as we get full-disk color at highest resolution (given current predicts of the rotation).
Looking at 17:48:30, so looking at the worst case scenario I am not actually suggesting starting that early, Io is still in the JunoCam FOV. We lose Masubi as it isn't quite in the FOV yet, but Shamshu and Janus would be there, Janus would be a bit more marginal there. My point is that even in the worst-case scenario for the rotation phase, 17:49 would still be useful for gap filling. For added context, during IVO planning we had an entire flyby just to get this coverage.
For context, Janus is a lava lake much like Pele. In the IR, Janus looks almost identical to Pele, but has fewer volatiles (IOW, there's no giant red ring around it)
Have you compared the amount of Jupitershine in this encounter with the previous one? It looks similar, but I was surprised reviewing the PJ51 imaging that the nightside was much dimmer than it was in PJ57.
Probably this is just a Jupiter phase and Io orbit position thing, but the tools I have to look at this are clumsy.
comparing 55C00035 with 57C00030 and 57C00022, I get roughly similar pixel values for places like around Fjorgynn Fluctus. Color still looks better for the PJ57 images. No apparent signal in BLUE in the orbit 55 images, it looks to be almost entirely noise. for PJ57, the darkest features like Guawa Patera and Fjorgynn Fluctus and the brightest terrain shows up (bright material near Gauwa and Fjorgynn, and around Acala Fluctus). I presume that this is a factor of noise, reducing effective resolution. So PJ57 data, particularly 57C00022 looks great, but the effective resolution is still reduced by a factor of 2-3 compared to the dayside. but that drop of resolution still makes it better than Galileo/Voyager data.
Even for my simulations, I account for the JunoCam FOV by looking at the predicts in Cosmographia and trimming off the excess in Photoshop from the maps I reproject in ISIS.
as far as the timings go, 17:48:30 is even more marginal than 17:50. It does do some gap fill east of Shamshu Patera but it misses Masubi and barely gets Janus. If that's just how the timings work, I mean, that's still really nice resolution at Shamshu and points east. 17:53:30 looks pretty good though maybe reverse the TDIs? 17:53:30 is good for a nice full global shot in sunlight.
Regardless, I'm sure these will be amazing. I'm so thrilled that we are getting such great sub-Jovian/leading-hemisphere coverage!
For posterity, Jason's last message arrived too late to affect command generation, so what I said on 1/12 reflects what we commanded.
I'm never sure how timestamps work on this forum, I'm sending this at 12:46 PST or 20:46 UTC on 1/16.
Now, we wait.
With the timings and TDI settings Mike provided above, here are preview images (combining USGS basemap with PJ57 data, greyscale is USGS basemap and a simulation of Jupiter-shine):
Thanks! How will the resolution on Loki compare to PJ57?
John
The resolution will roughly match JNCE_2023364_57C00023_V01, so the second of the images from the last encounter, and at a similar emission angle, but at higher phase angles (110° vs 90°). JNCE_2023364_57C00022_V01 had better pixel scale at Loki, but at a higher emission angle.
Apparently there is going to be a live event with Q&A starting at 9:30 PST tomorrow (2/3) at https://twitch.tv/nasa if that's of interest.
I don't expect the data to be on missionjuno until sometime Monday 2/5, though I have been wrong about this before. There may be some pre-C-kernel images out earlier on social media.
Thanks for the heads up Mike. I did let me D&D group know that I might be busy Sunday evening just in case... My legally distinct "Han Solo" character can sit out a session.
Full images aren't up yet, but the green filter of one of the crescent sunlit images is now available:
Here's an effort to align the Loki imagery in green from PJ57 and that first green frame PJ58, to emphasize the specular effects.
This brings back memories of the specular glint seen off Titan's lakes.
BTW, not the first time we’ve seen specular reflection at Loki:
Wow! This is a beautiful image of Loki, far more so than the I32 Galileo image. And I think there are even some topographic shadows visible at Loki, the best example I can remember of this in images showing Loki.
And the great thing is also that this image implies that the Io flyby was a success (at least for JunoCam). No 'PJ56-like' problems.
New Horizons also got a nice view of strong specular reflection from Loki (red arrow in the attached) at 150 degree phase, albeit at low resolution. The blue arrow points out that the bright deposits around Ra Patera are also very forward scattering.
John
Io images are up on missionjuno now. https://www.missionjuno.swri.edu/junocam/processing
PJ58_24 closest approach image from 1499.3 km altitude.
Nightside of Io illuminated by Jupiter-shine.
Needs some cleanup, but not too bad.
Wow, the specular effects at Loki vary tremendously between those two images. This flyby is going to provide some unique, perhaps definitive, information about the reflectance of Io's surface.
The Jupitershine imagery is also great.
The only thing mitigating the pure surprise is that PJ57 was already so good, but this adds tremendously.
PJ58_25 again, stretched, to bring out hint of plume in upper left.
Looks like Masubi lives!
These images are awesome. They must be by far the best images ever obtained of specular reflections on Io. This is image 26 enlarged by a factor of 2. North is up. I haven't been this excited by new planetary images for a long time (but they appear at a terrible time for me - it's now roughly 3 am where I live!).
sorry if the question has already been posted,
What are those that look like lakes filled with?
and does Loki contain magma or a liquid?
Daniel
According to previous temperature measurements, the greater part of the surfaces around Loki, while definitely warmed by internal heat, were far too cool to be liquid.
In fact, coincidentally, they are roughly comfortable for human presence!
https://www.sci.news/astronomy/map-loki-patera-jupiters-moon-io-04854.html
So that would be compatible with a solid surface that is glassy.
On the other hand, Io brings uncertainty across time and fine scales of space, so maybe what we're seeing now is different.
Yes, wonderful images. It's interesting that the northernmost patera of Mazda Catena, the site of a strong specular reflection here, was very likely also the location of a specular reflection seen by Voyager 1 45 years ago https://photojournal.jpl.nasa.gov/catalog/PIA00021. The temporary brightening was interpreted at the time as a blueish cloud emitted by the patera, but it's more likely that it was a specular glint, that was strongest at the time when the blue filter image was taken.
The most striking thing about the Loki specular reflection is how uniform it is- that's telling us something interesting about the resurfacing process.
John
Wonderful images of a wonderful world. Thanks to all for posting. Jason, I notice that the horizon/limb topography seems to be missing or at least muted in your versions compared with, for example Brian Swift's post 41 which has more the feeling of being in a real landscape. (The horizontal orientation helps too.) This encounter calls to mind the excitement of New Horizons at Pluto even though it's not our first look at Io.
Just two different methods of processing the data. I use ISIS which has the issue of it trimming the images off at the limb when you map project them. But on the other hand they are very useful products for dropping them into ArcGIS.
A map-projected comparison of images PJ57_24 and PJ58_26:
Has anyone managed to actually spot an impact crater on any of these new images?
As far as I know, no one ever has, but they must be there even if resurfacing is common.
Also, Bjorn, are those specular reflections off peaks at the bottom of your right hand (new Juno) image?
P
We just recently had a first suggestion of an impact crater in old data:
https://eos.org/articles/amateur-astronomer-finds-a-possible-crater-on-io
Juno would not be able to see craters like that one.
Phil
"Twenty-kilometer diameter craters are made by kilometer-size impactors; such events occur on a Galilean satellite about once in a million years."
https://pubmed.ncbi.nlm.nih.gov/11878353/
Io's surface is "no more than a couple of mission years old."
I don't know what a fair extrapolation is for the rate of cratering for that could be seen in these images, but it seems like it would be very optimistic to hope to see one, and zero is the likeliest number. The ambiguity in appearance adds to the difficulty. (Even on Earth, the cause of origin of weathered, extant craters can be ambiguous, and we're not observing them from orbital distances!)
This is an updated plot of the values I use for correcting the color in the JunoCam images. It shows the now well known reddening of the images as the mission progresses. Interestingly, the reddening trend became more irregular once the first JunoCam anomaly occurred at PJ48. In particular, the images temporarily became less red after PJ48 but are now again getting redder - there was a very large change (reddening) from PJ57 to PJ58.
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.
A further processing of http://www.unmannedspaceflight.com/index.php?act=attach&type=post&id=54541 from post #48.
Colors enhanced using principal components analysis, image enlarged with Upscayl. North is to the left.
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
Wen JIRAM images?
The PDS release calendar is here: https://pds.nasa.gov/datasearch/subscription-service/data-release-calendar-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...).
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.
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