(Started a new thread to avoid cluttering up the PJ57 thread with PJ58 discussion.)

I'll do what I can. There are a whole bunch of constraints. Io goes through the FOV rapidly around 17:50 and we can only command a maximum of four images at fixed cadence before incurring a 30s delay. I can't improve the nightside coverage at the cost of degrading the dayside, the best of which happens around 17:51:30.

I'm surprised that people are getting a lot out of the TDI 2 nightside images. I guess they're better than nothing but I was expecting at least TDI 6 would be required if not more, which means the dayside would be blown out for sure.

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:


A possible drawback is if the PJ56 problem returns at PJ58. If that happens, red images will be much better. So if possible, it might make sense to also take at least one red-filtered Jupitershine image just in case.

NOOOOOO. PJ56 problem is not coming back before PJ112.

Compare the progression of black offset and noise during PJ56 (a lot) with that in PJ57 (practically none). Even if PJ58 proceeds like PJ56 did (which we hope is unlikely) most of the change would happen after the Io encounter.

We hope.

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Map for PJ58 Io flyby from SPK. Ground track covers the distance of +100.000/-100.000 km.

EDIT: fixed night shadow.

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.

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I updated the flyby map with new information above.

Thanks. But without seeing where the Junocam FOV is along the ground track, it may be hard to understand why I picked the times I did. Visualizing this on a flat map is tough, as I well know. These times were a product of going back and forth in Cosmographia repeatedly, looking at the evolving FOV coverage.

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.

I'll look at it. Keep in mind that all of these times are +/- 15s and I can only take four images in a set before incurring an additional delay. I could start the third set earlier but only at the cost of dropping the last image it currently has, which I was reluctant to do. I tend to not value the nightside images that highly, but maybe that's the wrong bias to have.

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I made another visualisation of the flyby, including Jason's suggestion for 17:49:00.
No attempt was made to account for Juno's distance from Io, attitude or FOV.

Pretty, but the FOV is rather important. 17:49 just doesn't have much of Io in it.

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for 17:49 this is what I get:

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This does add coverage to the west of what 17:50 can get, particularly Masubi, and at decent resolution, 1.1 km/pixel at center of disk. 17:53 doesn't seem to add much and some of that can be recovered by starting the last set a minute earlier (17:55)

I will note that the leading hemisphere is the other big gap in our map of Io where the best resolution data from Galileo/Voyager/New Horizons was ~7–8 km/pixel and this would definitely help fill that gap.

17:53 is a backup against timing errors or possible unrecoverable loss of 17:52.

There are constraints on how close the sets can be and I don't think the last set can be moved in.

But I hear you and I'll see what I can do.

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.

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Here is a set of preview images starting with the 17:49 opportunity and including 17:53. The last image is the 17:56 opportunity. There is no meaning to the difference in brightness in the Jupiter-shine areas, just me being fast and quick in Photoshop and not paying attention to what exposure setting I used.

Except Junocam isn't seeing the center of the disk at that point. IMHO 17:49 is too oblique.

I considered bumping everything back 30 seconds so starting at 17:49:30 but that's not a clear winner to me either, thoughts?

And you have to consider that due to spin phase uncertainty the position is uncertain by a spin period.

Whatever we do, I have a soft deadline of EOD today to decide.

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.

I think the difference (wait for it) is that Jupiter doesn't shine on the part of Io away from Jupiter, only on the part facing Jupiter. Duh.

So one shouldn't expect Jupitershine on inbound-to-Io images, only on outbound-from-Io images.

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I'm not totally sure, but I believe it is possible to present above discussion in a map form.

The view above shows Io as seen from Jupiter at the time of the flyby. In other words, the center of map projection is at Io's sub-Jupiter point.
This means we are looking at the hemisphere illuminated by Jupiter-shine.

I've used this article to estimate how much of Io's disk Juno can see at selected times.
(17:49 in red, 17:49:30 in green; 17:50 in blue). I used values of 0.25, 0,265 and 0.28 respectively for f to account for the rising altitude, giving me range circles for parts of Io visible to Juno at these times.
You can really see how much the coverage changes in very short time.

I still have to account for Junocam FOV as I suspect not the whole visible disk fits into the camera view, but I haven't figured out how to account for that yet.

And yes, there is no Jupiter-shine on the inbound track.

It's not easy. To do it completely correctly, you need to know the pointing of the spacecraft as a function of time. For many of these flybys, including this one, the spacecraft spin axis (Z) is pointed at Earth, which makes it a little easier. So the Junocam FOV is a locus roughly +/- 30 degrees from the XY plane and spun about the Z axis. If a point on Io is in that locus we can see it, if it's not then we can't. I could imagine sampling a full range of lat/lon, checking to see if that point was in the locus, and drawing a little X there if it was, or something similar.

BTW, after much analysis I decided I couldn't take an image at 17:49, but one did fit at 17:48:30 so I took one there with TDI 12, then three images at 17:50 (TDI 12), 17:51 (TDI 2), and 17:52 (TDI 2). All RGB.

2024-034T17:32:00 RGB 6, 2
2024-034T17:39:00 RGB 2, 12
2024-034T17:48:30 RGB 12
2024-034T17:50:00 RGB 12, 2, 2
2024-034T17:53:30 RGB 12, 6

You have until Monday to change my mind

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.

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I made some progress querying SPICE. Here is what I think might be a plot of Junocam's boresight projected on Io's surface for the period from 17:32 to 17:56.
The plot looks a little confusing and I'm still studying how this information might convert to image footprints for specific times.

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):

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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:

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Reflective Loki! the Xihe plume! Jupiter Shine!

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:

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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

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Io images are up on missionjuno now. https://www.missionjuno.swri.edu/junocam/processing

First pair of images complete:

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PJ58_24 closest approach image from 1499.3 km altitude.
Nightside of Io illuminated by Jupiter-shine.
Needs some cleanup, but not too bad.
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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.

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First attempt at the second Jupiter shine image. Need to work on the control network a bit more on this one so this is a first draft.

PJ58_25, altitude 2493.8 km, Jupiter-shine illuminated.
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PJ58_25 again, stretched, to bring out hint of plume in upper left.
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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!).

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A plume is visible at lower right. This part of the image is heavily processed and has been brightened significantly relative to other parts of the image to show the plume more clearly.

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Improved versions using a global control network

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-pat...n-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.