Europa Flyby - PJ45, September 29, 2022 Options

[Bjorn Jonsson]

Images PJ45_3 and 4:

[Bill Harris]

FWIW, Junocam is not a pushbroom. There certainly shouldn't be any significant chromatic aberration, but there are plenty of ways for different color framelets to get misregistered, and that's probably more likely the farther you go from the optic axis.

So I agree with John.

It is indeed a type of pushbroom.
At any rate, it ain't chromatic aberration, which is purely optical.

"In addition to visible light filters, it also has a near infrared filter to help detect clouds; a methane filter in addition the visible color filters. The camera is a 'push-broom' type imager, generating an image as the spacecraft turns moving the sensor in sweeping motion over the observation area.[10]"

[Brian Swift]

Low Res PJ45 Jupiter Images overview exaggerated color/contrast.

(Edited)Full resolution version at https://www.missionjuno.swri.edu/junocam/processing?id=13963

[scalbers]

Here's an approximate remapping of Bjorn's PJ45_2 image (in grayscale) blinking with the earlier map.

[StargazeInWonder]

Nice work, scalbers!

It seems that maybe because Juno was so close to Europa that projecting the imagery as though the distance were infinity creates some significant distortion near the limb.

It's very nice how the coverage here happened to fill an area where existing coverage was particularly lacking, particularly in the north.

At a glance, it looks like the new imagery reveals some dark linea in the north that didn't exist before, but a less sensational explanation would be that the linea vary in visibility as a function of viewing geometry and that previous imagery was simply incapable of observing them. But I'm sure we'll hear an expert review soon.

The other thing that would be interesting to learn from this is if the slippage of Europa's icy shell over ~25 years is large enough to be detectible. The details near the terminator are extremely sensitive to the exact rotation between now and any points in the past. We know that the slippage occurs, and maybe 25 years is enough to give us the first direct measurement of it.

[scalbers]

Thanks StargazeinWonder - I was assuming a projection distance from 4 Europa radii. This can be adjusted now that I found the actual geometry on the Juno website. Indeed the illumination geometry and contrast are different, some adjustment of things may be possible along with adding some color info.

[djellison]

At any rate....

You just cited a wikipedia page...which in turn is wrongly using a citation which is a paper on which Mike is a co-author.

https://www.missionjuno.swri.edu/pub/e/down...each_Camera.pdf

No where will you find the phrase pushbroom in that paper.

Because JunoCam - as Mike VERY correctly points out ( as he is - after all - the JunoCam systems engineer ) is NOT a pushbroom camera.

It is a pushFRAME camera which is very different.

It's probably best to trust the paper itself ( and one of its coauthors you were arguing with ) rather than a Wikipedia page editor who wrongly cited it.

[scalbers]

A 4K version of the earlier Europa blinking comparison, with more accurate mapping:

https://stevealbers.net/albers/sos/jupiter/...uropa_blink.gif

UPDATE: PJ45_4 now added.

[StargazeInWonder]

That's a much better fit, scalbers! I'm sure that it took a lot of work. Also, it does a lot to resolve the question of "new" linea in the north. Because the existing imagery came from more than one (usually, in any area: one or two) different illuminations, we can see clearly that in some cases, the same linea appears dark in some earlier imagery, and light in others, then dark in the Juno imagery. I guess this is because of the interaction between some locally extreme topography and albedo, with a raised linea appearing lighter than (or the same brightness as) the background terrain when viewed fore-lit from the side, but darker than the background terrain when viewed from basically any other angle. Ultimately, we're not going to have a seamless map of Europa until we have every part of the surface viewed from approximately the same geometry… but until then, this work is great!

[Bjorn Jonsson]

That's a much better fit, scalbers! I'm sure that it took a lot of work. Also, it does a lot to resolve the question of "new" linea in the north. Because the existing imagery came from more than one (usually, in any area: one or two) different illuminations, we can see clearly that in some cases, the same linea appears dark in some earlier imagery, and light in others, then dark in the Juno imagery. I guess this is because of the interaction between some locally extreme topography and albedo, with a raised linea appearing lighter than (or the same brightness as) the background terrain when viewed fore-lit from the side, but darker than the background terrain when viewed from basically any other angle. Ultimately, we're not going to have a seamless map of Europa until we have every part of the surface viewed from approximately the same geometry… but until then, this work is great!

The relative contrast and brightness of various features on Europa is known to vary a lot depending on viewing geometry, even when the illumination geometry doesn't change much. Here is a particularly interesting example I posted somewhere years ago, a map-projected blink comparison of Galileo G1 and E14 images:



The image with overall lower contrast was obtained during Galileo's G1 orbit and the other one during Galileo's E14 orbit. These two images were obtained when the illumination geometry was very similar but the viewing geometry was not. The viewing geometry can be seen below:

[StargazeInWonder]

What a perfect illustration, Bjorn. The topography of the ridges is visible and makes clear why the appearance depends so much on the geometry.

[scalbers]

Here's a color blinking 2K sized comparison:



Links for 4K comparison and 4K map.

The "map" version has some optimization of where the Juno vs Galileo / Voyager imagery is being used.

[ZLD]

Here's a color blinking 2K sized comparison:

Great comparison. Now, when do we get to argue over which has the more correct color?

[Daniele_bianchin...]

I image that never haven't an fantastic high resolution image like 12/m pixel Conamara Chaos from Galileo SSI?

https://planetary.s3.amazonaws.com/web/asse...haos_schenk.jpg

Attached thumbnail(s)

 

[Bill Harris]

You just cited a wikipedia page...which in turn is wrongly using a citation which is a paper on which Mike is a co-author.

https://www.missionjuno.swri.edu/pub/e/down...each_Camera.pdf

No where will you find the phrase pushbroom in that paper.

Because JunoCam - as Mike VERY correctly points out ( as he is - after all - the JunoCam systems engineer ) is NOT a pushbroom camera.

It is a pushFRAME camera which is very different.

It's probably best to trust the paper itself ( and one of its coauthors you were arguing with ) rather than a Wikipedia page editor who wrongly cited it.

I called it a "pushbroom type" of camera, as did Wiki, referring to the general type of sensor on a rotating spacecraft. So, pushbroom, pushframe, whatever. No arguement intended, I learned there were different types of that type of system.
"At any rate", I was questioning whether the blue fringe was chromatic abberation. Correctly, it appears to be misregistration of the color channels.