Galileo Io

[Darryl Roy]

Here's a peek at an attempt to colorise the medium resolution Galileo probe Io basemap with the true(r) colors revealed by the Galileo probe:



Full texture available here:

http://www.geocities.com/inequity30/io-1st_draft.txt

(using the geocities .txt trick)

Only posting this preliminary view because I'm so psyched that using a freeware image warping/morphing tool to warp the BADLY out of register Galileo 1.3k color map available for the JPL solar system simulator (I used about 70 reference points, and it still needs tweaking) with the USGS Io Galileo b/w mosaic.

Galileo b/w coverage, where it exists, is superior to Voyager coverage, but has huge gaps on hemisphere facing Jupiter. Voyager coverage is much more complete, but its color (with violet & near IR faking the red, and little color callibration) is badly off, and difficult to fix in the RGB color space.

The next step is to 1) warp both the Galileo b/w and color images into the reference space defined by Voyager coverage, 2) merge the Galileo & Voyager b/w maps, 3) colorise with low res Galileo color.

When done, it should dazzle on the 'splash screen'.

[Darryl Roy]

Another attempt to get the image to work:



Compare to:

[/img]http://antwrp.gsfc.nasa.gov/apod/image/0210/iosurface_gal.jpg[/img]

If they don't, the URL's are

memorex:
http://www.geocities.com/inequity30/io/io-1st_draft-snapshot.txt

real:
http://antwrp.gsfc.nasa.gov/apod/image/0210/iosurface_gal.jpg

[Darryl Roy]

Yikes. HERE is the first draft, presented as a 4096x2048 jpg.

http://www.geocities.com/inequity30/io/io-1st_draft.txt

As it turns out, the Galileo color mosaic I was using (the only one I've seen, only used color images through orbit 6 or so. Much better is
possible, if one is willing to warp more hemispheres sized mosaics into the correct reference space...[/url]

[selden]

Darryl,

Instead of using a morphing program that you have to tweak point by point, you might want to investigate Iris by Christian Buil. Its MAP commands include the ability to remap from telescopic views of hemispheres into "simple cylindrical" image projections like those Celestia uses. Iris does seem to have some off-by-one bugs, but it's usable.

[Darryl Roy]

Selden,

Thank you for the pointer.

I doubt it will entirely solve my problems, as I don't know, from the hemispheric projection (or assembly) of these images, just where the
North pole is. And if that's off (even fractionally) the whole image will
be seriously out of kilter - most likely at a slant.

I was originally working with an image reported to be in simple cylindrical projection - and it seemed to be altered from an original in sinusoidal projection, but it was still out of register, and in a very irregular way, setting one definable point to match the reference map (at the same scale) other points seemed to vary quite irregularly (N,S,E,W, in no prevalent pattern). Clearly I was working with some mishandled (somewhere in the chain) mosaics, but with a little play in BitMorph (which either has serious memorly access issues or had a virus tagging along...)
I was able to resolve most of them.

However, now that I found a trove of good hemispheric images (of Io, and Europa as well) I think I should be able to pull off a decent 4k all-real Io and 8k (with part fictional bumping) Europa...

[Darryl Roy]

A couple hours learning IRIS, and now I've got one hemisphere done,
in Galileo true colors in near-full resolution (downsampled a factor of about 0.75). The registry with the Voyager basemap may wait a short while:





Unfortunately, the other full hemispheres I've seen are slightly lower resolution, have lighting issues, and are in 'enhanced' color. I think they
are fixable to nearly this standard though. Two more hemispheres (for overlap), and Galileo Io is done..



[/img]

[selden]

Darryl,

You might want to consider using Celestia's AltSurface declaration and/or "Limit of Knowledge" masks to help indicate which parts of the surface map(s) come from which sources.