Galileo images and mosaics of Europa Options

[vexgizmo]

Does anyone know what the composition of those brown areas are?
And did they come from the ocean floor?

Probably sulfur-rich materials from charged particle bombardment of salts and/or sulfuric acid hydrate, which in turn may have churned upward from Europa's ocean. But no one is sure... part of why we need a new mission, with a better spectrometer.

[vexgizmo]

Im certain it would be possible to do that, I did some fast dabbling with the small one you provided, but as soon I zoomed in I noted the jpeg noise and well...at least I would feel it more rewarding to spend time on if one had a larger sized image than that so one wouldnt get artifacts from masking the various parts.

Here is blue

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[vexgizmo]

...and green...

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[vexgizmo]

...and red (near-IR, really).

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[Guest_Myran_*]

Thank you vexgizmo for the samples, since the last one was near ir, and only covered a smaller part of the area I ended up working on two colours. Part reason was that while working on the image I noted that some stripe of the blue channel was out of aligment, seems to me it was one layer below where two others images have been pasted on top.



But not entirely certain, I adjusted that at best of my ability though. In the end we see one completely unscientific interpretation of mine.

[Exploitcorporati...]

A second, equally unscientific attempt at colorizing the E6 transect from your new data :

[vexgizmo]

Gaw-geous!!! Are you able to colorize E6ESDRKLIN01 with this? And certainly not "my" data; Galileo's data! Well, everyone's data now

[Exploitcorporati...]

E6ESDRKLIN01...first attempt:



Credits-
Background mosaic: NASA/JPL
Color processing: Myron
Color overlay: Exploitcorporations
Concept: vexgizmo
Images:Galileo

[Exploitcorporati...]

Just for S&G, a badly tweaked version of the 1997 false-color JPL release:

[ljk4-1]

To quote:

Our good friend Arthur Clarke, who wrote of Europan life in his novels, in a letter dated 27 May 1997, described the picture as being the "most extraordinary ever received from space.......".

http://www.cf.ac.uk/maths/wickramasinghe/europa.html

[Guest_BruceMoomaw_*]

Yes, and -- unfortunately -- he suggested, apparently seriously, the possibility that one of the bands in it was actually an artificial roadway mde by aliens. Alas, in his old age Arthur seems to have been possessed by the evil spirit of Richard Hoagland.

[Bjorn Jonsson]

I have been trying to make (true ?) color images of Europa using mainly Galileo data. I am using red (IR756 in some cases), green and violet images. The violet images have considerably more contrast than the green images. Using Voyager images as a crude guide it seems the blue images have a contrast somewhere between the contrast in the green and violet images. Because of this I also made synthetic blue images as B=(G+V)/2.

I am attaching two preliminary versions of my images, one image using G1 data (IR756, G and V) and a C10 image (R, G, V). Images using V and synthetic blue are included. I should be able to get more realistic results in the future, the color balance is just a crude guess and it would be more accurate to use synthetic red instead of IR756. The red images have a bit higher contrast than the IR756 images so using synthetic red would be more realistic. Also it is probably not very accurate to use the exact average of green and violet as blue. A weighted average should be more accurate.

I eventually plan to use this to colorize a huge (roughly 10000x5000 pixels) global grayscale map of Europa I am working on. When complete it should be of slightly higher quality in terms of coverage than the USGS map. To colorize I need to remove limb darkening etc. because it varies with wavelength, making the color 'change' towards the limb. My biggest problem is that I do not know the wavelength-dependent photometric parameters for Europa. Does anyone know if Hapke parameters as a function of wavelength (or Galileo filter) are available somewhere ?

BTW I also did something similar (synthetic blue) for images of Io, see http://www.mmedia.is/bjj/3dtest/io/index.html for details.

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[ugordan]

Somehow the IR-G-V images look more "natural" to me than the ones with a synthetic blue channel. I find the orangish colors more natural than the pinkish ones using a synthetic blue channel.
That preference may have its roots in the Voyager imagery so one comes to expect an orange colored Europa -- not neccessarily its true color at all.

[Big_Gazza]

Err.. this may be stupid question (here it comes...) but if my $150 digital camera can take a true(ish) colour picture in a single take, why can't space probes? (well, at least the modern ones built with digital technology).

(this is where the image-processing experts roll their eyes and curse the ignorant noobs )

[edstrick]

A consumer digicam usually has one CCD, and except for the Foveon CCD now being used in a few cameras, it cannot see all three colors with each hardware pixel. Instead, each pixel has either a red, green or blue single-pixel color filter in front of it. The standard design has a checkerboard pattern with 1/2 of the squares being green pixels and the rest are alternating red and blue.

When the data is read out from the CCD, smart software compares adjacent pixels and local brightness trends and makes a smart educated guess for what the missing two colors's brightness SHOULD be at the location of each pixel. It works. Pretty well. If you're not fussy.

That's why Pro-sumer video cameras often have 3 CCD chips and use special "dichroic" filters to let one color through and reflect another directly to that color's CCD. They're more sensative, since no photons are being absorbed, and each matched set of 3 pixels detects all the red, blue and green light that aren't randomly lost in reflection and transmission.

Spacecraft cameras, like Mariners, Viking Orbiters, Voyagers, Galileo and Cassini use one or two filter-wheels in front of cameras to swap a wide variety of filters in front of the single CCD, which you CAN'T do with a color-mosaic CCD like the ones in a consumer camera.

Some, like the MER camera filters split up the entire spectrum entering the cameras into fairly regularly spaced segments so a full set of narrowband MER filter images adds up to a 11 measurement spectrum of light entering the camera from violet to near infrared.

Galilleo and Cassini cameras also have narrow band filters that are specially designed to measure brightness in a narrow part of the spectrum. In their case, they measure light reflected from Saturn and Titan in bands where methane strongly absorbs, and you can use a set of methane and non-methane band images to measure the height <or depth> of clouds and hazes in the atmosphere. Cassini also has a set of polarizing filters to measure the polarized scattering of light by gasses and cloud/haze particles, which depends strongly on size and shape of cloud particles.

To take "TRUE-color" images, you have to design a set of color filters who's transmission varies with wavelength so that when combined with the transmission of the optics and wavelength dependent response of the camera CCD <or vidicon on old missions> you fairly precisely match the red, blue and green responses of "standard" color vision. To do that, you end up with a set of filters that are less ideal for scientific purposes, like estimating a surface spectrum as in the MER cameras.

MSR is planeed to have "hi-def" camera capabilities in color, and I suspect those detector/filters will be mosaic types, as in consumer cameras and camcorders. Even if color data from them won't be "full scientific grade" in quality, it will still be more useful for navigation and spotting "interesting" targets to look at closer than the monochrome hazcam and navcam images.