[X] My Assistant

[volcanopele]

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/

[Bjorn Jonsson]

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.

[volcanopele]

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

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.

[mcaplinger]

JunoCam might be able to do decent Jupiter-shine imaging...

The main issue with the encounters is the spacecraft spin and the maximum cadence of imaging. So we can't take images as quickly as we might like, it may take 2-3 spin periods between images. And we have data volume constraints as well. We could use a lot of TDI for nightside imaging, but it frankly hadn't occurred to me to try it, and I'm not sure how well it would work. But this is something we could try for the earlier Io encounters to see if they would be worthwhile for the close ones.