Voyager and Galileo Images of Ganymede, The Ganymede images and mosaics thread Options

[EDG]

Cool. That looks like the set I used in this one.

[attachment=22801:gancol1fvoyager1.jpg]

Very nice! What filters did you use for that? I thought I'd used all the available images in those filters in mine, but maybe I ran out of steam and missed a few.

[ugordan]

EDG, any idea why you have color shifting in the 3-color footprints near the terminator? It looks to me the green and blue filters are darker there than their neighboring footprints, causing some reddening there. For fun I tried coaxing your O+UV color near the left limb to the OGB in the center and I can get them to match more closely than the actual OGB footprints agree.

[EDG]

EDG, any idea why you have color shifting in the 3-color footprints near the terminator? It looks to me the green and blue filters are darker there than their neighboring footprints, causing some reddening there. For fun I tried coaxing your O+UV color near the left limb to the OGB in the center and I can get them to match more closely than the actual OGB footprints agree.

Are you referring to what looks like some of the component images near the terminator being different brightness/contrast to the others? (e.g. the voyager image on the bottom right of the green mosaic looks darker than the surrounding images)? I'm not sure why that's like that - I think the images might not have been calibrated properly relative to eachother? I'll see if I can find my scripts for this one and see if there's any clue to what's going on in there.

[ugordan]

Are you referring to what looks like some of the component images near the terminator being different brightness/contrast to the others?

Yes. I assume all the frames were taken at roughly the same time so the terrain illumination as well as phase angle are pretty much constant? It looks like a calibration thing. I guess I didn't expect to see that much calibration uncertainty with ISIS, although I've never really worked with it or Voyager images in general.

See the red strip near the terminator and a yellow-green bit below it - the part of the terminator that looks ok is a synthetic red channel.

[tedstryk]

I am trying to find my notes...I did that image three or four years ago. I'm pretty sure I used OG(B+UV) where I could. Where I couldn't, I used whatever was available and shifted it to match the color in wide angle shots.

[EDG]

Yes. I assume all the frames were taken at roughly the same time so the terrain illumination as well as phase angle are pretty much constant? It looks like a calibration thing. I guess I didn't expect to see that much calibration uncertainty with ISIS, although I've never really worked with it or Voyager images in general.

See the red strip near the terminator and a yellow-green bit below it - the part of the terminator that looks ok is a synthetic red channel.

Yeah, I see that... I wonder if Ted ran into the same issue when he made his mosaic? I don't see the same problem in his image. I'm still looking for my script for this one, maybe that'll reveal an explanation.

[tedstryk]

I didn't notice that problem.

[tedstryk]

Here is my latest version of Galileo's E6 mosaic (with help from other orbits).

[elakdawalla]

That is lovely. Is the shift from reddish tones to more gray (or more blue) colors from mid-northern latitudes to northern polar latitudes real or a result of some boundary between image coverage?

[tedstryk]

Toward the poles, it definitely seems grayer.

[EDG]

I've found the scripts for the Voyager 1 mosaics, but they are broken down into individual filters. It also looks like I did it as a two-stage process - I have one script that updates the SPICE labels with the RAND data using spicelab, and then I have the script that makes the mosaic (which refers to the rmb file created in the first part of the process). Each filter's zipfile contains a RAND#.rmb that's already been generated. Does anyone know if this is even necessary anymore, or has the SPICE data been updated to something more accurate in the years since I did this?

So here's the scripts for each filter. The randcolour.zip file is the SPICE label updater but for all the images involved in all the filters that I use here - it just puts the updated data into a single file called RAND.rmb, instead of separate rmb files for each filter. Unfortunately I don't have a single script file that you can edit to make all the mosaics at once.

As before, I'd advise looking through these files and checking that they'll work in your system (e.g. the cd2isis command in RANDcolour.txt script refers to IMQ files mounted locally, so that won't work without being changed). You'll also have to look at the scripts to see what IMQ files you'll need (easiest way is to check the input2.txt files) And use the scripts at your own risk .

Attached File(s)

 globalblue.zip ( 5.88K ) Number of downloads: 319
 globalgreen.zip ( 4.5K ) Number of downloads: 335
 globalorange.zip ( 4.75K ) Number of downloads: 349
 globalUV.zip ( 3.8K ) Number of downloads: 333
 globalviolet.zip ( 5.9K ) Number of downloads: 319
 randcolour.zip ( 6.31K ) Number of downloads: 358

 

[ugordan]

It's supposed to be an irradiation thing - the boundaries roughly match the latitude where magnetic field lines transition from closed (equatorial region) to open (polar) so charged particles can spiral down there and pepper the surface. Or so I've read.

[DrShank]

thats right, those are the aggregate effects of small scale deposits within the two polar caps. well documented. also very visible in the Atlas in global views and at high resolution, where it is seen as pole-facing bright deposits

Attached thumbnail(s)

 

[tedstryk]

Here is an alternate color mix.

[ngunn]

Titan has veiled wonders and Io suppurates, but to my eye from a distance Ganymede is just the most beautiful moon in the solar system. Thanks to all for the magnificent images.