At today's Outer Planet Assessment Group (OPAG) meeting, Scott Bolton gave a presentation on Juno, providing an update on the mission and providing more information on its extended mission proposal. The proposal has been sent to NASA and they expect a final decision later this year.

The proposed extended mission starts where the current one ends at perijove 34 in June 2021 and continues through orbit 76 in September 2025. The continued northward progression of the perijove latitude, and continued lower altitude of the ascending node, is going to enable a lot of great science both at Jupiter (higher resolution views of Jupiter's poles) and of its satellites. Most excitingly for me, Juno will perform several flybys of the Galilean satellites. This includes a 1000-km encounter with Ganymede next June during PJ34, a 320-km encounter with Europa in late 2022, and TWO Io flybys in early 2024 at an altitude of 1500 km. There are also a number of "Voyager-class" encounters with Ganymede, Europa, and Io between mid-2021 and mid-2025.

The PDF for Scott Bolton's presentation can be found on the page for the OPAG meeting: https://www.lpi.usra.edu/opag/meetings/opag2020fall/

That is exciting.

I know that the eye candy is fun for all of us, and this forum is a particularly good medium (and talent base) for image processing but I am getting increasingly interested in the less-flashy and slower-to-evolve science on the interior of Jupiter and the synergistic study of the interior of Saturn that capitalized heavily on the last phase of the Cassini mission.

The status, on a meta-level is that Juno has placed some important constraints on the interior structure of Jupiter but there's still a lot of uncertainty regarding the details and no consensus regarding Jupiter's origin. I don't know with what certainty more perijoves will answer those questions, but the questions are important and more perijoves sure can't hurt.

It's also very interesting that Jupiter and Saturn are significantly different internally.

All of that said, I'm also looking forward to the Galilean eye candy. There could be some important science there, in advance of Europa Clipper getting to the vicinity.

And it won't just be eye candy with the Galileans. For example, the Europa encounter will allow for mapping of one hemisphere with the MWR at 100-200 km resolution. That instrument can probe to a depth of 10 km allow for the direct detection of lakes within the Europan ice sheet. The Io encounters will include JunoCAM imaging sure, but also JIRAM mapping of Io's hotspots with resolutions down to 355 m/pixel as well as gravity science and magnetometer measurements, which when combined with future IVO passes, will provide some strong constraints on the state of Io's lower lithosphere and upper asthenosphere.

For Jupiter, with closer passes over the poles, they will be able to do better 3D mapping of the atmosphere below the north polar cyclones as they will be able to do repeated passes over the same part of Jupiter.

I would like to see the assumptions that went into that, it seems very doubtful to me. Scattering by fractures, and absorption by contaminants (salts, sulfuric acid..) in Europan ice is such that even the sort of 10 MHz ice penetrating radar on Clipper has a good chance of not penetrating that deep, and the ~1 GHz MWR wavelength being 100 times shorter will sound commensurately less deep.

I'm curious if the Europa imagery could be sufficient to determine the rate of rotation of the shell/surface, which is not synchronous with the core. It's known that the rotation rate of the shell relative to the core is very slow, and the baseline between Voyager 2 and Galileo was not sufficient to measure visibly any rotation. The time from Galileo to Juno imaging would be, once again, about 20 years, but the resolution of Juno imaging would be higher than that of Voyager 2. Getting any measurement of that rotation, even to first order, could tell us a lot about the dynamics of the shell, in which the major linea represent cracking along stress lines that must have taken place when the shell was oriented very differently with respect to Jupiter. But since then, has it undergone ~0.25, ~1.25, ~2.25, etc. full rotations?

Ralph, thanks for the dash of reality. Hope that the microwave instrument provides some new insights. (BTW, Ralph, your new Titan book is excellent. Been enjoying it.)

One thing not mentioned so far in this thread is that Juno will conduct a "sensitive" search for Europan plumes. Will use the camera and the much more sensitive star sensors.

I'm certain it will. Any time you use a new instrument on a target, you make discoveries. And the MWR is an exquisite instrument.

But one must always (both post-hoc for 'discoveries', and pre-hoc for 'opportunities') consider the motivations behind any claim. Fame, tenure etc. can be the prize of high-profile publications, so there is often a 'race to the bottom' for the lowest standard of evidence that will satisfy peer review for 'discovery' of something exciting - claims of discovery of cryovvolcanism on Titan are a case in point. And some of the higher-profile scientific journals are complicit in this process, they like the headlines. Similarly, claiming that a mission/instrument/observation may discover X is not a disprovable statement, and is a rational thing for someone advocating for said mission/instrument/observation to claim as a possibility. But that isnt the same thing as saying dispassionately that it is an expected result.


Cheers! Tell your friends ! oh, I guess you just did ;-)



That is potentially a very interesting observation. (And not unrelated to my earlier point : the discovery of plumes on Enceladus is, reasonably, attributed to the Cassini magnetometer team. But in fact the Cassini imaging team saw evidence of the plumes before that, but wanted to be sure that what might have been a plume wasn't some scattered light artifact in the images, and so waited to get more data. Because they (laudably) imposed on themselves a high standard of proof, other evidence emerged first and they got perhaps less credit than they might have deserved).

So, the fact that the Juno Mag/SRU - in effect a low-light camera - is so sensitive is great, and it has had some nice results detecting lighting, but this alone does not necessarily make it a good plume detector. Careful characterization of the scattered light response of the camera will be essential for robust plume detection.

Again, there are temptations in plume detection to give oneself the benefit of the doubt in marginal situations, both for individual scientists, and for 'selling' a mission (the timing of the first reported HST plume discovery, at very low signal to noise, I might add, was let's say fortuitous with respect to the timing of Congressional support for what became Europa Clipper). So it is rational in the run-up to a senior review for a mission extension to note the instrumental sensitivity and the observation opportunity, but some careful scrutiny may be in order before one raises expectations too high. (the OPAG presentation did not permit the PI to present much detail - it may well be that a strong case for the MWR detection of Europa's ice thickness, and the SRU detection of possible plumes exists, I just note that I haven't seen it yet.)

All this is only natural, science is a human process. You only find the evidence if you think it is there in the first place. But as Robert Louis Stevenson said, 'The cruelest lies are told in silence'......

It may be that the contribution of Juno's microwave observations may be to characterize how noisy observations of the the ice shell's structure will be. Bolton had less than a minute to describe the microwave observations, and as I recall, I believe that he said that the instrument had the capability to observe as deep as 10 km, not that it would observe that deep.



Off topic, I would like to see an MWR like instrument flown on an ice giant mission (and some proposed missions would include it), but its mass is a significant issue. I saw that Bolton has a grant to do technology development for a lighter weight and more capable version with an eye toward an ice giant orbiter.



I agree. Ignore the press release, read the paper. (Even better, wait for the synthesis review of papers that weighs evidence from a number of studies.) I did look up the original Europa plume paper, and the authors, as I recall, did state that the observations were right at the edge of detector capability. Then NASA made the most of it, as they did for the claim that the Martian meteorite had fossilized micro organisms. Will say, that NASA is good a parlaying press releases into missions (or in the case of Mars, a whole program of missions).

The SRU is unrelated to the magnetometer. Maybe you're confusing it with the magnetometer's ASCs (Advanced Stellar Compasses)?

On this thread in general: The mission extension proposal will be quite detailed, and evaluated carefully. I think criticizing it on the basis of an OPAG overview presentation is a little inappropriate.

I agree with Mike. Putting moderator hat on...

Some these questions would've been great to bring up during the Q&A part of the OPAG session on Wednesday, but without Scott Bolton here to better explain the factors that went into their claims or the hedging that might have gone into their actual senior review proposal (which for the vast majority of missions are much more detailed than a PDF presentation), it might be best to drop the discussion of MWR performance at Europa for now. And without details on how exactly they will be looking for plumes, again, we need to be careful about speculating then criticizing what we speculate.

Taking moderator hat off...

That being said, with the SRU being used for science as well as navigation, I do hope that the Juno team considers posting that data to the PDS.

Sorry, I'm not a mission insider, yes I meant the magnetometer's star camera (which I guess happens in this instance to be called an ASC - a strange name : a magnetometer has a compass that isnt a magnetometer ;-)

And I didnt criticize anything or anyone. I merely said I'd like to see more analysis backing the claims that were made, and I made general observations about the scientific process.

Will images be taken during Europa and Io Encounters?

Will they be comparable to Voyager 2 Best images?

Once more for clarity: there are multiple star cameras on the spacecraft. The SRU (two for redundancy, one active) is an engineering subsystem and the ASCs (four total) are part of the magnetometer, used for getting high-resolution orientation data for the magnetometer to remove the effects of boom motion. They can all be used for imaging, but it's the SRU that has been most used for low-light imaging and radiation monitoring at Jupiter.

I don't have any information on planned instrument usage, but the closest satellite flybys would certainly allow imaging at much higher resolution than Voyager 2 at Europa. Note that the satellite flybys in the presentation span a huge range of distances and the farthest ones are similar to the opportunistic imagery already acquired during the main mission.

My sense from the distances is that the main scientific playoffs will be:

1) The spectral range of Juno instruments in making hemispheral maps of Ganymede and Europa hinting at composition. It will be the spectral capabilities here that add to the knowledge more than the spatial resolution.
2) A search for Europa's plumes.
3) Monitoring the current activity of Io volcanoes.
4) Perhaps contributing original detailed mapping of Europa on the one really close encounter.

Considering that the resolution of the Voyager ISS NAC was 72x higher than the resolution of Junocam at the same distance, I'm not sure I'd say "certainly". If the closest approach was 320 km and if illumination conditions and spacecraft orientation were compatible with imaging there, then the maximum resolution Junocam could get is about 0.2 km/pixel at nadir. JIRAM could do about 3x better.

The Bolton presentation says 1-2 km resolution.

I'm not sure what the best resolution image of Europa from Voyager was, but there is global coverage at about 0.5 km/pixel from a mixture of Voyager and Galileo https://astrogeology.usgs.gov/search/map/Eu...bal_mosaic_500m although there are some gaps where the coverage is much worse or (near the south pole) even missing entirely.

Digging up my copy of the Voyager 2 Jupiter encounter imaging report (Smith et al. 1979, Science ), I see that Voyager's best resolution on Europa (from Voyager 2) was 2 km/pixel. So Juno could easily do better.

John

The best resolution images of Europa by Voyager 2 were at around 1.33 km/pixel so the resolution quoted by Scott Bolton would be in that ballpark.

As Mike says there are large gaps in high resolution coverage of Europa, so the close imaging may indeed improve mapping in some areas. For Io even fairly low resolution imaging (though I still mean an order of magnitude better that existing Juno images) would show surface changes, and we know they are frequent and substantial. Certainly good science to come from that. It doesn't look like there are useful opportunities for small satellite imaging.

Phil

With regard to improving resolution, keep in mind that the satellite encounters can't be done for the convenience of imaging and the geometry is highly constrained by the spacecraft spin and spin attitude, so anything we get in that regard will be largely serendipitous.

And of course the extended mission is subject to approval and funding.

Am I correct that Juno doesn't photograph Callisto? Is Callisto's orbit too far out of range?

Occasionally Juno gets to within 650,000 km or so of Callisto so it would appear about 10 pixels across, but that's it. I'm not sure if the geometry works out such that Callisto appears in the Junocam FOV.

When will the extended mission be approved or not approved?

Knowing we have a chance to study Europa in the next three years has my nerves on overdrive.

The decision is expected in December. Perhaps more important than simple approved or not approved (it seems unlikely that NASA will shut the mission down on its first extended mission request), is the budget. A smaller budget than requested could mean less is done. NASA has a fixed pot of money to fund all of its extended planetary missions, and I'm sure that the managers for the other missions are also making compelling cases for their science.

The results of the 2020 Senior Review and NASA's response have been posted

Response

Report


Some highlights from NASA's response:

Juno Extended Mission
- Juno is approved for an extended mission from August 2021 until September 2025. NASA expects that the mission end-of-life will occur during this period.
- Juno will continue observations of the Jovian system as the spacecraft’s periapsis processes northward and to lower altitudes. Juno will utilize additional propulsive maneuvers to perform close flybys of Ganymede, Europa, and Io.
- Juno will continue to explore major scientific questions related to Jupiter’s interior, structure, and atmosphere, including the polar vortices, the magnetic ‘Great Blue Spot,’ water abundances, and the Jovian aurorae, focusing on observations enabled as the periapsis moves northward.
- The EM will add targeted observations of three of Jupiter’s large satellites. Imaging observations will search for changes since Voyager and Galileo, and observations with the spacecraft’s Microwave Radiometer will explore Europa’s ice shell. In situ measurements of Jupiter’s ring system will explore their structure and characterize their dust population.

Obviously I am VERY EXCITED to see this approved so we will get some Io flybys in 3 years! Buried in this SR report is a note that NASA is asking the Juno team to archive SRU data from the nominal mission. Happy to see this for some of the eclipse observations of Io from PJ16 and PJ25.

Yes!!! More eye candy!!! We return to the Galileans!!! (poor Callisto though)

This is great. Will Juno be in position to capture more polar views of the moons, like it did with Ganymede awhile back?

It did, but not the unmapped area.

I expect a much better resolution!

If the regions that had no previous coverage were going to be imaged, I think it would have said something different. However, we won't really be sure until the new maneuver design is finalized what each encounter will look like, and there are many constraints on s/c attitude that also factor in.

Large Swaths of Ganymede may be improved depending on how close it is. Though don't expect anything like Solid State Imaging.

Mike, do you know yet if MSS will be doing any additional (beyond current operations) JunoCam work due to extended mission?

Planning the satellite encounters and processing the results is obviously beyond the scope of what we've been doing so far, so yes.

Bolton's presentation to OPAG (linked upthread) said the minimum altitude of the Ganymede flyby was 1000 km, at which Junocam would get ~670 meters/pixel resolution. It's a bit hard to say what the best resolution in the current coverage is, but it's probably better than that in most places, and the gaps are near the north and south poles, which AFAIK won't be seen in this encounter. As I said, we won't know for sure until the final flyby geometry is established. Note that this first Ganymede flyby is in mid-2021.

[I guess I should mention that my perspective is obviously Junocam-centric and JIRAM will also get images, which are both higher-resolution and not subject to the limitations of darkness.]

Magnetometer science at the Ganemedian magnetosphere might be interesting too. Are the flyby geometries favourable?
I know the magnetosphere is tiny.
Also - imaging of the Ganemedian ultraviolet aurora!

P

ps I better read those posts, maybe its in there. I'm excited though. Always great to get bonus unexpected science (thinking of Deep Impact etc)

Start with https://www.lpi.usra.edu/opag/meetings/opag...Bolton_6011.pdf and
https://www.lpi.usra.edu/NASA-academies-res...nior-Review.pdf

It doesn't look like the final extended mission proposal from Juno was made public, so you have to infer what it may have said from the review of it.

The SPK file for the current baseline (which may change) is at https://naif.jpl.nasa.gov/pub/naif/JUNO/ker...1021_210111.bsp if people want to look at it.

See https://naif.jpl.nasa.gov/pub/naif/JUNO/ker..._210111.bsp.lbl for info on the flybys.

Expect an animation of the Io encounters on YouTube by end of day (it will assume HGA to Earth pointing, which at least for the Io flybys based on the OPAG presentation is a reasonable assumption)

Placeholder post for Io flybys based on spk_ref_210111_251021_210111.bsp :

ground track map:

Click to view attachment

Neat view before the PJ57 encounter:

Click to view attachment

...because radioscience?

Groundswaths are very exciting!

This map (from here:)

https://astrogeology.usgs.gov/search/map/Ga...IM3237_Database

shows image coverage for the USGS basemap of Ganymede. There will be small areas of high resolution coverage scattered through this.

It suggests to me that any swath of imaging from Juno's closest pass will improve our maps to some extent.

Phil

Click to view attachment

Looks like best imaging along terminator at around 48°W. best "swath" looks centered around 30 W, covering 15 south to 70 N

Click to view attachment

That map reminds me of the early Cassini days of observing Titan and anticipating what will we find with each swath. Similar with Io since it changes so much.

Something like that, but note that I think this is a little past closest approach. We come in on the night side so the best visible imaging is on the outbound leg, where the resolution is going down fairly quickly.

It'll be cool regardless, but I don't want to oversell it.

Ganymede was actually fairly well imaged by the Voyagers since V1 flew by Ganymede when outbound whereas V2 did so when inbound. Later Galileo filled some gaps (plus limited 'postage stamp' hi-res images).

However, there are some really poorly imaged areas on Europa because only one of the Voyagers (V2) obtained moderate resolution images and most of the many Galileo flybys occurred over the antijovian hemisphere (also the HGA problem prevented the return of lots of gap-fill images from non-targeted Europa flybys like G7). The coverage is especially poor near longitude 130 degrees and there are also some 'annoying' patches of low resolution coverage near longitude 70 degrees and longitude 320 degrees. I haven't checked the new Juno SPKs yet (e.g. spk_ref_210111_251021_210111.bsp) so I don't know if Juno has opportunities to image these areas at better resolution but I suspect not.

The two close Io flybys look interesting to me since the ground tracks posted above are over a relatively poorly imaged area.

Of course this is exciting but I suspect the satellite data from JIRAM or even the magnetometer may turn out to be far more interesting than the JunoCam data. That said, I'm especially interested in seeing the JunoCam coverage of Jupiter's north polar region. The north pole will soon be in sunlight which is great and saves me from becoming frustrated by the fact that the north pole will be in darkness when JUICE arrives at Jupiter and will still be in darkness at the end of the mission (there is an inclined phase during JUICE's tour, allowing it to view the polar regions). So we get to see the north pole during summer after all.

Here is the simulation of the best Europa view I found:

Click to view attachment

Closest approach is over the nightside. Best views over the sub-Jupiter hemisphere.

Very excited to see Europa and Io!

Does Amalthea come close to being imaged?

Very curious to the fallout from Io on its surface.

Keep in mind that most of the "poorly imaged area" will be in darkness. The terminator will be at around 330 W, so features like Ra and Loki will be illuminated. That being said, the PJ31 images of Io, while not that great in terms of resolution, do suggest to me that JunoCam might be able to do decent Jupiter-shine imaging. Mike would be better placed than me in knowing how well the JunoCAM sensor might perform when imaging a target that is illuminated at 1% of Solar. the effective resolution would be lower due to poorer signal-to-noise, but I don't know how much "play" sequence planners have in adjusting exposure time to deal with the weaker illumination conditions.

Juno gets to within 42000 km of Amalthea on 2025-07-13 but it will only be 8 pixels or so across.

Remember that the encounters with the Galileans are as much about changing the orbit as about doing satellite science, and Amalthea is not useful for the former.

And even with JIRAM, Amalthea would be 25x12 pixels in size. still, it could get some disk-resolvable NIR spectra.