Juno Perijove 49, March 1, 2023 Options

[volcanopele]

Okay, I will just have to be patient. They will come in PJ49. It just means that I will skip processing one of the Io RDR images from PJ43 that hits that same splotch until the PJ49 comes down.

[StargazeInWonder]

Very interesting, Bjorn.

Your comments on the further anomalous details of the reddening (eg, the effect being greater in PJ48 than in PJ 49), as evidenced on the blue line, seem also to appear, to a lesser extent, on the green line. One might try to verify this statistically, and narrow the number of degrees of freedom at work.

This is probably grasping at straws, but I wonder if there is any additional feature in any of the images that might constrain the source of the effect. Eg, do Saturn, Earth, Sirius, etc. ever appear as a background object that could measure the effect on another known reference object? Given that Ganymede was too small to serve in that capacity, I guess anything outside the Jupiter system would also be hopeless in this regard. Io, on the other hand, has now appeared in multiple PJ imagery, but has its own remarkable variations in color that might disqualify it for the purpose, unless the same terrain has appeared several times.

[Kevin Gill]

New departure movie using frames taken from March 1st to March 20th. Unfortunately the Galilean Moons are hardly visible and, when visible, aren't more than a pixel in size.

YouTube:
Jupiter - Perijove 49 Departure Movie

[Bjorn Jonsson]

From the BAA Jupiter Section Juno PJ49 report:

"For the third successive perijove, some images were lost, this time apparently corrupted by radiation, as Juno’s evolving orbit now entails more exposure to Jupiter’s radiation belts than before. The missing data were inbound images over a few hours before the Io flyby, and all the closeup images from the N4 domain to the SEBn"

I haven't seen anything official about this yet though.

[Tom Tamlyn]

I guess I haven't been paying enough attention, because I don't know what "the N4 domain to the SEBn" means. Some googling and forum searching didn't find anything.

I'd be grateful if someone would explain.

[mcaplinger]

I guess I haven't been paying enough attention, because I don't know what "the N4 domain to the SEBn" means. Some googling and forum searching didn't find anything.

The Jupiter community loves their acronyms and rarely bothers to explain them any more. N4 ("northern northern northern northern") https://britastro.org/section_information_/...3-to-n6-domains is the middle part of latitudes 43 to 64ºN. SEBn is "a superfast prograde jet at 7S" https://britastro.org/jupiter/epsc/EPSC2011...ct-SEBn-jet.pdf -- I think SEB is southern equatorial belt, n is the northern part?

I've complained about this (to my mind obscure) nomenclature to the point of being obnoxious, but you have to call stuff something and this is traditional.

[Tom Tamlyn]

Thanks Mike!

[Tom Tamlyn]

And thanks especially for elegantly providing references in context.

I've complained about this (to my mind obscure) nomenclature to the point of being obnoxious, but you have to call stuff something and this is traditional.

"[N]orthern northern northern northern" gets points for whimsy. Also, in my experience the annoyance to outsiders of obscure jargon is balanced by the satisfaction it gives to insiders when they sling the bat, thus preserving felicific equilibrium.

[Bjorn Jonsson]

These BAA reports assume that the reader is familiar with the belt/zone nomenclature. It is explained here (includes a nice diagram):

https://britastro.org/jupiter/programme.htm

Lots of acronyms. The "B" at the end of an acronym means "belt" (they are dark) and "Z" means zone (they are bright/whitish). A "T" means "temperate" and "Trop" means "tropical". So e.g. SSTB is the "South South Temperate Belt". The width and color of the belts/zones varies though and sometimes the narrow ones disappear temporarily even though the zonal wind speed at the relevant latitudes doesn't change when this happens.

There is also some interesting information here: https://britastro.org/jupiter/guide.htm

[Explorer1]

It doesn't seem that much more complex than the permanent features we humans can attach names to on solid bodies.
Earth's meteorology divides the planet in a similar fashion, and we even name large storms that never lasted as long as the GRS/Oval BA.

[Tom Tamlyn]

Bjorn, thanks for those helpful links.

And continual thanks to you and all of the experts and specialists here for sharing your work on UMSF.

[Brian Swift]

Mike,
Can you say if there is an explanation for the increase in "noise floor" between
JNCE_2023075_49C01628_V01-raw.png "IMAGE_TIME": "2023-03-16T21:00:30.042"
and
JNCE_2023075_49C01632_V01-raw.png "IMAGE_TIME": "2023-03-16T22:00:27.920"

Plot of mean of raw values. The above times corresponds to the discontinuity on the right.

[StargazeInWonder]

Those scalloped-shaped changes look like the change in temperature that results when a new level of heat is applied/removed and a system adjusts to the new stable temperature.

Kepler, as an example, had noise driven by temperature, and as the spacecraft changed configuration, and the heating of different parts of the spacecraft by sunlight began or ended, the sensors had noise levels adjust to that change. However, that happened very intermittently with Kepler, which had stable pointing for ~90 days at a time, while Juno is spinning and the geometry is changing constantly.

However, "looks like" is just suggestive, not an explanation. And as for the abrupt jumps, those look like a different beast altogether. Note that when Juno approaches Io, it is also approaching radiation belts and the Io flux tube, so there's potentially a lot going on that can excite electronics.

[mcaplinger]

Mike,
Can you say if there is an explanation for the increase in "noise floor"...

I don't think it's necessary to call me out by name. Others may have answers and it just makes me feel bad if I can't respond.

As Stargaze has correctly intuited, these are temperature-related and intentional. I can't say more, but one might search for phrases like "radiation damage" and "room-temperature annealing". Once the PDS volume has been released, it should be fairly obvious what's going on.

[Bjorn Jonsson]

Earlier in this thread I posted a plot showing the color correction multipliers I was using for each perijove. Here is an updated version where PJ50 has been added. It looked interesting to me and looks even more interesting after reading several of the preceding posts.



The images now appear to be getting *less* red after a more or less continuous reddening trend since ~PJ20. The PJ50 values are preliminary though and based on only a single image, image PJ50_53. I will be examining more images and this might result in slight changes to the PJ50 values here but I will be very surprised if there are any major changes.

I don't know if the red channel is now getting darker or if the blue channel (as well as green) is getting brighter but it should be possible to determine this.

Image PJ50_53 has a 3.2 msec exposure time whereas image PJ49_91 (a comparable image) has a 6.4 msec exposure time. I don't think this is a significant factor but cannot rule it out yet.