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

[Hungry4info]

That's very nice!

[tedstryk]

Superb work!

[Juramike]

Beautiful!

[Bjorn Jonsson]

One more example of what can be done with the Voyager images using modern computers and software. This is one of the best Voyager mosaics I have seen of Ganymede and of course much better than any of the official stuff produced back in 1979.

[machi]

Thanks!

Yes, new reprocessed images from Voyagers are mostly better than old official versions, but I have great respect to people who made this old images.
With much slower computers and not very user friendly software, it must have been really damn difficult.

[tedstryk]

Many were processed using a VAX. I can't even imagine it.

[jasedm]

Very impressive Machi.
The terrain in the far south near the terminator is incredibly similar to Enceladus' south polar terrain (on a much larger scale of course)

[Ian R]

Brilliant work, Daniel!

I'm beginning to think that a website based upon the NASA Planetary Photojournal site, but dedicated solely to 'amateur' image products, might be a good way of collating the ever-growing portfolio of great work produced by people on here. We could even call it the 'UMSF Photojournal'.

Oh, Ted: I used to own a VAX. It was the best darn vacuum-cleaner I've ever had...

[machi]

Ian, I have actually similar idea and in fact it's partially on the way. Because I haven't my own server, I must use public server with 300 - 500 MB data storage.
So I suppose, that in first phase I will create simple gallery with my images (png's) and then (second phase) I will be using only thumbnails with location reference to full image or page with image.
There is minor problem with my programming skills, so I will plan only simple html gallery with thumbnails and basic informations about every image.

[EDG]

This is a colour global view of Ganymede, taken using Orange, Blue and Violet images (in the RGB channels respectively) from Voyager 2. I made it using ISIS around 1998 or 1999, it's an orthographic reprojection of a mosaic of the antijovian hemisphere. I don't think I stretched the histograms in the component images at all.

I wish I could remember what specific images I used (I'm reasonably sure that I was using the images that start around C2063105). Annoyingly I can't find my notes on it - I'm lucky I actually managed to find the image itself! . I think there were around 39 images in total (about 13 for each filter)?

I do remember that I had to manually match the images - I didn't have IDL or any of that other fancy stuff, working in a UK university that didn't have the funds to buy it. I looked at each adjacent/overlapping image pair in a given filter, looked for a minimum of three match points between the images, and noted down the pixel locations for all of them in a little black book and in a text file that ISIS would read, and then did that several times for each overlapping image pair - it took weeks to find all the match points, and sometimes ISIS would still just not match the darn thing properly and so I had to go back and find different ones. As it is it nearly broke the computer I used to make it (which of course was great for the time and completely laughable by modern standards), and I think the end mosaic (in original .cub format) was over a gigabyte in size! I'd have to leave the ISIS script to take it from level 0 to level 4 running overnight and hope it all worked. I also used updated SPICE data for Voyager that I got from Tim Colvin at RAND Corporation (that IIRC wasn't in ISIS at the time). The resolution of the mosaic is 2 km/pxl.

Probably not awesomely useful for science, but I'm pretty proud of it considering the effort it took to make it - hope you like it .

[DrShank]

>>I wish I could remember what specific images I used (I'm reasonably sure that I was using the images that start around C2063105). Annoyingly I can't find my notes on it - I'm lucky I actually managed to find the image itself! . I think there were around 39 images in total (about 13 for each filter)?

yep those are the numbers. it was a 3-color 6-frame mosaic (18 total). i dont know why it didnt cover the poles. the basic color patterns of ganymede are in this mosaic: the reddish color of dark terrain, the different colors of the dark rays, even the bluish polar caps in a few spots. i used it in the Atlas to fill certain areas but used lower resolution Galileo color because that included IR data globally.

[tedstryk]

One of my Ganymede mosaics uses that set with wide angle data for the poles.

[EDG]

Only 18 images? Seemed like a lot more! (maybe I'm thinking of how many overlapping pairs there were, or something).

So barring the slight difference that using OBV filters instead of RGB ones would make, is this actually close to the colours that Ganymede would have if we were there looking at it with our own eyes? There doesn't seem to be much of a colour/brightness difference between "bright" and "dark" terrains (the ejecta around Osiris is much more noticeably brighter though).

[ugordan]

So barring the slight difference that using OBV filters instead of RGB ones would make, is this actually close to the colours that Ganymede would have if we were there looking at it with our own eyes?

It's pretty close, I'd say. FWIW, I ran your image (great mosaic, btw!) through some code to interpolate the entire visible spectrum (linearly between OBV wavelengths) and convert to sRGB:



The brightness is due to gamma-correction, the actual color is similar to yours, only less reddish/brownish.

[EDG]

Very nice! Thanks for doing that, I've often wondered if there was any software that could interpolate between the filters.