30th Anniversary Voyager 2 at Europa, a hint of things to come Options

[DrShank]

It seems to be a season of anniversaries over the next year or so.
20 years since Voyager 2 at Neptune (see my posting there), 30 yrs since Voyager 1 at Io,
30 since Voyager 2 at Europa, 30 years since VEJUR at . . . . well never mind!
plus all the Galileo 400th commemorations (I will have more on that next week).

I thought it would be a good time to start a thread on this one, which occurred on a
tuesday morning in July 1979. Although the images had been taken on July 9, they were
recorded for playback the next day. I was a mere summer intern in those days and was attending
the morning briefing along with the rest of the Sci Support Team of which i was a member.
Linda Horn and Ellis Miner were my gurus that wonderful summer. Playback was scheduled for
sometime between 8 and 9, as i recall, and I can still remember looking up at the monitor
as the first high resolution images ever seen of Europa first appeared. Wonderful, even
tho only 2 kilometers in resolution. Little did I know where it would lead me . . .

Here is a restored version of one of the two mosaics returned that day. They hint at some of
the exotic things that Galileo later discovered.

cheers
paul

Attached thumbnail(s)

 

[Bjorn Jonsson]

Yes, the same dataset with one exception: I didn't use any of the wide angle images for color, I only used narrow angle data. The drawback of this is the absence of green filter data but as mentioned above I don't think that's a big issue. But it's not always easy to know exactly how accurate the resulting color is.

One 'crazy' color processing idea I have is to somehow use Europa's entire visible spectrum together with the color information from spacecraft images to compute an entire synthetic, visible spectrum for each point in an image and use this to make synthetic R/G/B. I'm not sure exactly how I would do this but this would replace the linear interpolation that is usually used, both when mixing the color channels as I did above and also when the entire visible spectrum is created from (usually) three filters and then converted to sRGB. I doubt this will work very well though but I'm interested in trying it. One obvious complication is that the leading and trailing hemispheres have slightly different spectra and obviously the spectrum of a dark feature is different from the bright terrain. And there is no spectral information available in visible light that resolves these small (relative to Europa itself) features and also has high spectral resolution.

[JRehling]

Bjorn, I share your crazy dream. I think Europa's entire surface can be represented fairly well as a pointwise blend of three or four surface components. Then the subtasks would be:

1) Determine the Hapke parameters of each of those components, based on areas where the surface is a relatively pure representative of that component.
2) Determine for as much of the surface as possible, what the local coefficients are that weight how much the various components contribute.

Once this process came along, it would probably be possible to make some pretty good estimates of (2) based even on single-filter images.

And then one could render realistic color images of much of the surface of Europa even where no such images have been captured.