Galileo images and mosaics of Europa Options

[tedstryk]

I have worked on sprucing up some global views of Europa from Galileo. There are a few more global views I hope to get to eventually. But the best two at nearly full phase benefited a lot.



[Moderator note: There are several more threads containing Galileo Europa images but they all contain several inactive image links. The main threads are:
http://www.unmannedspaceflight.com/index.php?showtopic=2016
http://www.unmannedspaceflight.com/index.php?showtopic=2174
http://www.unmannedspaceflight.com/index.php?showtopic=2222
http://www.unmannedspaceflight.com/index.php?showtopic=2082
http://www.unmannedspaceflight.com/index.php?showtopic=2142 ]

[deglr6328]

Wow, I do believe that bottom one is the most spectacular view I have ever seen of Europa. Well done! Is that one true color? Interesting to contrast it with what Voyager saw.

[Bob Shaw]

Yup. Verrrrrry good!

[edstrick]

That Voyager view is the best color mosaic view, but the image quality of that version is poor. A bit fuzzy and with a bad color-cast.

[Decepticon]

WooHoo! My favorite LittleMoon! I love Europa.

[tedstryk]

That Voyager view is the best color mosaic view, but the image quality of that version is poor.  A bit fuzzy and with a bad color-cast.

In my galileo mosaic, the color data is a mixture of two band data from the orbit, as well as a crude reprojection of data from other orbits. So the Voyager mosaic is best.

[tedstryk]

That Voyager view is the best color mosaic view, but the image quality of that version is poor.  A bit fuzzy and with a bad color-cast.

In my galileo mosaic, the color data is a mixture of two band data from the orbit, as well as a crude reprojection of data from other orbits. So the Voyager mosaic is best.

I think the super-res effect really helped them.

[tedstryk]

In my galileo mosaic, the color data is a mixture of two band data from the orbit, as well as a crude reprojection of data from other orbits.  So the Voyager mosaic is best.

I think the super-res effect really helped them.

I am also working with Voyager...Here is the best Voyager 1 set, in OGB color.

[tedstryk]

I have worked a bit more....I am having OGB Voyager problems. To the right is the image as produced through standard processing. To the left is a version edited to try to look more like a Galileo image.

[tedstryk]

I just made an exciting "discovery" - well, a discovery to me...there is one more global color view in the Galileo set from the C10 orbit. I am surprised this hasn't been used more. The Color is IR-7560-Green-Violet. However, the green image clips the terminator, so that area is filled in with a synthetic green from the IR-7560 image and Violet image. The black and white image is a combination of a super-resolution image produced from the IR-9680, IR-7560, and Violet image, all of which were transmitted after being binned 2x2, and, for the areas available, the green image was then merged creating an even better product.

[Phil Stooke]

Ted - fabulous! Keep it up!

Phil

[scalbers]

These can be compared with the cylindrical map that is on my website at http://laps.fsl.noaa.gov/albers/sos/sos.html#EUROPA

[tedstryk]

That map is awesome...I hve spent much time admiring it.

As for the color mosaic, I have tried many times to make it, but I have hit pitfalls. First, the lack of green data on the terminator. Second, when I try to fill it in with lower resolution data, it looks odd, since the green image is the only one sent back at full resolution. Third, the albedo patterns looked wierd, because the green filter data was used as for the grayscale. By making a super-res image from the binned imagery, I was able to prevent a great resolution drop on the terminator and was able to make a more realistic grayscale image without degrading it with low resolution input. By overlaying the green image over a synthetic green created from violet and IR data, I was able to make the end of the green image less noticeable.

The only other galileo global shot of Europa was from the e17 orbit. I have crudely matched it with other color data here...I will put more time into this someday. I also plan to eventually work on the G1 data and merge it with some other data for a global view.

[JRehling]

Ted - fabulous!  Keep it up!

Phil

Ditto. My silence belies awe and gratitude.

John

[scalbers]

Ted,

Your images are very nice as well, particularly the large gibbous view in post #1. One thing in particular I'd consider is comparing the hue and saturation realism to what I had used, namely the colors from Bjorn's map (that I may have tweaked a bit). Do you have a feel for the pros and cons of the color accuracy compared with Bjorn's? Both look pretty good to me - I wonder what new insights you have come up with. I'll reread your posts as well.

[paxdan]

nice work on europa guys. It is so cool to see the images being properly reproduced instead of horrid stuff you still see in text books.

[tedstryk]

Ted,

Your images are very nice as well, particularly the large gibbous view in post #1. One thing in particular I'd consider is comparing the hue and saturation realism to what I had used, namely the colors from Bjorn's map (that I may have tweaked a bit). Do you have a feel for the pros and cons of the color accuracy compared with Bjorn's? Both look pretty good to me - I wonder what new insights you have come up with. I'll reread your posts as well.

Be careful of that image. The filter sets available were limited at best, and those used to produce the image vary throughout. Plus, some color data is from the actual set the grayscale image was made from, but a lot of it is from different orbits at different illumination angles. So the color, while processed to seem roughly realistic, is quite treacherous - a lot of guesswork went into it, and then I normed it a bit to fit the other images. As for the others, they are as accurate as I could make, but I can't directly compare them because I don't know how Bjorn's color was produced.

[Guest_Sunspot_*]

How about trying the same with images of Io?

[tedstryk]

I have thought of that. The only problem is that Io has much more color contrast than Europa (europa has some color contrast, but it is pretty predictable - Io's isn't). I am not sure if it would come out well or not. I may try.

[Decepticon]

Keep them coming! Europa really deserves an orbiter.

[tedstryk]

Keep them coming! Europa really deserves an orbiter.

Well, I might work on some other moons, or try some mosaics. This is the only other global view of Europa I could find in the Galileo set that was worth combining with some color data.

[Bjorn Jonsson]

Regarding my Europa map, the color there was taken from global Voyager images only. I used these to colorize higher resolution grayscale data (mainly clear filter). The reason I used Voyager and not Galileo data was higher resolution and IIRC Galileo had not imaged Europa globally in color at the time I made the map. I don't remember whether I used OGB or OGV (probably the latter) - I'm at work and can't check it now.

I'm pretty sure the color is a bit too saturated in my map. It may too reddish as well, a common problem when the wavelength of the data used for colorizing is too short (e.g. O instead of R and/or V instead of B ).

I have been working on a much bigger Europa map (9000+ pixels in the horizontal direction) from time to time for more than two years. I have reprojected most of the high-res data I plan to use but haven't started working on the color. I plan to use Galileo images for color where possible, filling gaps (or very low-res areas) with Voyager data and/or synthetic color. I also expect to use synthetic B instead of V. The V images are more contrasty than the B images but mixing G and V should give a fairly good results (definitely better than using V only). One thing that complicates color work is Europa's photometric properties, limb darkening varies with wavelength and I prefer images as close to zero phase angle as possible.

Ted's images look fairly good, especially wrt sharpness but there are some saturation problems, caused both by saturation in the red images (this manifests itself as pinkish areas) and in all of the images in some cases (bright, white areas). I have some early 'test images' of Europa that look similar. And I should add that there is great color data at 1.4 km/pixel in the E14 data.

BTW Europa's color should be kid's stuff compared to Io. There is some information on Io's color on my experimental renderings page ( http://www.mmedia.is/bjj/3dtest/ ) and I will add more once I make my new map of Io available, I've been too swamped in data recently to update my website . In particular, it is impossible to use 'unmodified' IR7560 as red without seriously messing up the color balance.

[4th rock from th...]

If you consider the Galileo filters and their wavelenghts, you have:

Violet - 404 : Green - 559 : Red - 671 : IR756 - 756 : IR968 - 968


The human color vision has a peak response of:

Blue - 440 : Green - 510 : Red - 650


So to "convert" the Galileo filters in to "human colors" we can mix images from different filters to get the proper wavelenghts.

I've calculated the ratios and corresponding wavelenghts:

75% Violet + 25% Green = blue (443)
70% Green + 30% Violet = green (513)
80% Red + 20% Green = red (649)
50% IR756 + 50% Green = red (658)
20% IR968 + 80% Green = red (641)


I've tried this on two Europa images and the results look good. Saturation is low, but that's expected when you mix the color data. Also, Europa looks white through a telescope anyway ;-)

[tedstryk]

I experimented with filter mixes. Realistically, the problem is that Galileo image quality varies wildly depending on compression used. Also, it is rare to get a color mosaic without some bad gaps. But I did use similar mixes.

Bjorn: I see the problem in my large mosaic, but could you point out what you are talking about in my other images? I am not sure which spots you are referring to, and would like to know so I can try to correct the problem. Some of what you are seeing may be due to the fact that I jacked the contrast up on the posted images.

[Bjorn Jonsson]

The pinkish areas are very prominent in the C10 image (the message dated yesterday at 05:29 PM), especially in the bright areas near the left limb and near Pwyll.

[tedstryk]

The pinkish areas are very prominent in the C10 image (the message dated yesterday at 05:29 PM), especially in the bright areas near the left limb and near Pwyll.

This is a tweaked version.



And another.

[Bjorn Jonsson]

These are better but still a bit pinkish. I'm not sure why - now that I'm at home and can have a look at what happened when I was processing these same images a few years ago I see I also had some problems with pinkish areas, especially near Pwyll. They were less pinkish but still pinkish.

Time to try to finish that 9816 x 4908 map of Europa I have been working on for two years, I should be able to get more realistic color for that map. I have now checked and seen that my current map of Europa was colorized using OGV as I thought. This means it is probably too reddish and saturated.

It is probably an interesting idea to check if there are any Cassini RGB (or CB1-GB) images of Europa near closest approach.

[scalbers]

If you try the CICLOPS site and use their new search feature for "Europa" a couple of nice (if small) color images will pop up.

[Decepticon]

Some "True Color" Images of Europa.

Somthing I found looking around. http://pirlwww.lpl.arizona.edu/HIIPS/EPO/gallery.html

[ljk4-1]

This could bode well for life on Europa (and Enceladus?):

Scientific American, 30 September 2005

http://www.sciam.com/article.cfm?chanID=sa...A8E83414B7F4945

Geologists have produced evidence of abundant marine life on the earth from a
period when others say a thick layer of ice gripped the entire planet. The find lends
considerable support to one side of a scientific controversy that has been widely debated for
decades.

The hullabaloo is over a glacial period dating to about 750 million to 600
million years ago.

Experts agree about the presence of ice on the planet then--even at the
equator--but how much and to what extent is still up in the air. Theories range from a "snowball
Earth" hard packed in kilometer-thick ice to a "slush ball Earth" characterized by thin ice and
areas of open water. The range of conditions would have impacted the microorganisms present.

Thick ice would have made life difficult for plants and animals, one line of reasoning goes,
choking oxygen out of the sea and blocking sunlight needed for photosynthesis. Mass extinction
would ensue and after the thaw, give rise to an explosion of multicellular life.

[Decepticon]

Has anyone here cleaned up this picture? It one of my favorite images of Europa http://photojournal.jpl.nasa.gov/jpeg/PIA02528.jpg

[t_oner]

Here is a rendering using my map.

Attached thumbnail(s)

 

[Decepticon]

WOW! Keeping that one!

Have anymore? Webpage?

[mike]

So many moons and planets, so little time.. perhaps the Planetary Society will get enough money for a close inspection of Europa sometime soon.

[Decepticon]

Europa has always capture my imagination.

I even dream of swimming around its oceans!

This leads me to a kinda off topic question. Has Europa ever been in a Hollywood movie besides 2010?

[t_oner]

Decepticon,

I don't have a website but I have contributed many maps to Calvin Hamilton's Views of the Solar System. The above Europa image is created using the map at:
http://www.solarviews.com/eng/eurmap.htm

[Decepticon]

Thanks!

[tedstryk]

Great work! I have always enjoyed your work on Views. Great to see you in this forum!

[vexgizmo]

Thank you all for the time and effort put into these beautiful Europa products! Ted, your E14-based Europa color mosaic is amazing. Sorry we couldn't get you that green-filter near-terminator strip returned to Earth....

-Bob P.

[ilbasso]

So many moons and planets, so little time..  perhaps the Planetary Society will get enough money for a close inspection of Europa sometime soon.

Can you imagine how many spacecraft we could build if France, the UK, Russia, and the US stopped building warplanes for just one year and diverted the money to space hardware? I know that's totally fanciful, and I know we need planes, and our military plays a vitally important role (and my son is a helicopter pilot in the US Army)...but would it really "kill" us to go one measly year without building new ones? We could fund many of the projects we would so dearly love to do. Think how much we could learn about our solar system!

Add it to your New Year's wish list!

Has anyone totalled up the surface area of the moons and major asteroids, even just a rough order of magnitude, and compared it to the Earth's surface area? Isn't it amazing to think about how much unexplored territory there is in our solar system? Once we get the technology to visit them, the human race will be busy for decades crawling over every nook and cranny.

[ilbasso]

Answering my own question: counting only the terrestrial and icy planets and moons, and not including any asteroids, comets or KBOs, the total surface area of the non-Earth "solid" solar system objects is roughly 281.7 million square kilometers, or about 2.2 times the total surface area of the Earth (including the oceans).

That seems low somehow.

But assuming it's correct, and assuming that an astronaut could explore 10 km^2 of surface area per day, it would take 28 million "person-days" to explore the surfaces of the moons and planets in our solar system. That sounds like steady employment well into the next century.

[vexgizmo]

Here's a challenge that I hope one of you might accept. During the E12 Galileo orbit, there was a sequence of Galileo color images obtained of Conamara Chaos. Below is work by the Galileo SSI team to assemble these into color mosaics. This color imaging is enough to paint much of the famous E6 Conamara Chaos mosaic in true color (or near-true color extrapolated from 2 colors)--unfortunately we still only see this region painted by false bluish color based only on the E4 Europa albedo images. Can someone accept the challenge of painting Conamara with its true E12 color?

-Bob P.

Attached thumbnail(s)

 

[ljk4-1]

Here's a challenge that I hope one of you might accept.  During the E12 Galileo orbit, there was a sequence of Galileo color images obtained of Conamara Chaos.  Below is work by the Galileo SSI team to assemble these into color mosaics.  This color imaging is enough to paint much of the famous E6 Conamara Chaos mosaic in true color (or near-true color extrapolated from 2 colors)--unfortunately we still only see this region painted by false bluish color based only on the E4 Europa albedo images.  Can someone accept the challenge of painting Conamara with its true E12 color?

-Bob P.

Does anyone know what the composition of those brown areas are?

And did they come from the ocean floor?

[Guest_Myran_*]

Vexgizmo said:  Can someone accept the challenge of painting Conamara with its true E12 color?

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.

I include the quick dabbling I did for reference though.



Edit: Images where each colour channel would be separated would of course be the very best.

[David]

Answering my own question:  counting only the terrestrial and icy planets and moons, and not including any asteroids, comets or KBOs, the total surface area of the non-Earth "solid" solar system objects is roughly 281.7 million square kilometers, or about 2.2 times the total surface area of the Earth (including the oceans). 

That seems low somehow.

Most of that must be Venus (9/10s of Earth's total area, including oceans; a vast territory to explore, if one could only get to it -- drat that Venusian atmosphere!).

Given that Mars' surface area is about the same as that of the whole land area of Earth, and the Moon's is about the size of Asia, and there are only five bodies intermediate in size between Mars and the Moon, yeah, that seems about right.

[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.

[Bill Harris]

Good explanation, Ed. Photography is all smoke and mirrors, whether it be black and white, grayscale, color, silver halide or doped silicon.

--Bill

[Bjorn Jonsson]

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.

The C10 (global) images look more 'natural' to me than the G1 images. This may be because I altered the color balance to make the area around Pwyll whitish whereas for the G1 image I didn't change the color balance. I should probably have changed it to something more similar to the C10 image. That said, I don't think Europa is as reddish as in the C10 RGsB image but I plan to use Cassini CB1GB images where both Europa and Jupiter are visible to see what Europa looks like when I process the image to make Jupiter's color balance similar to what one sees through a telescope.

[ugordan]

That said, I don't think Europa is as reddish as in the C10 RGsB image but I plan to use Cassini CB1GB images where both Europa and Jupiter are visible to see what Europa looks like when I process the image to make Jupiter's color balance similar to what one sees through a telescope.

You might have problems there because Cassini only used CB1 when it was still far away from Jupiter. Once the imaging plan changed to a 2x2 coverage footprint, they reduced the filter set and dropped CB1, leaving only CB2 as a close alternative. OTOH, I can't remember if they even kept the GRN filter coverage.
As a result, CB1 images of Europa are very distant and color differences will probably be unresolvable on such a small disk. My experiments with CB1 always resulted in Europa being more or less white.
There are a few RED/CB1 images taken near C/A IIRC, but they're severely underexposed, see my topic on Cassini Galilean images.
Note that in no way am I saying those colors I got are even remotely accurate (in fact, they're probably very wrong), that attempt was primarily driven by me wanting to know how well Cassini could resolve the moons from such a distance.

[vexgizmo]

Does anyone know if Hapke parameters as a function of wavelength (or Galileo filter) are available somewhere ?

Unfortunately, not yet for the Galileo data. This is the only photometric study I know of from the Galileo Europa data:

Helfenstein, P., N. Currier, B. Clark, J. Veverka, M. Bell, R. Sullivan, J. Klemaszewski, R. Greeley, R. T. Pappalardo, J. W. Head III, T. Jones, K. Magee, K. Klaasen, P. Geissler, R. Greenberg, A. McEwen, C. Phillips, T. Colvin, M. Davies, T. Denk, and M. Belton, Galileo obervations of Europa's opposition effect, Icarus, 135, 41-63, 1998.

The best from Voyager data is:

Domingue, D. L. and B. Hapke, Disk-Resolved Photometric Analysis of Europan Terrains, Icarus, 99, 70- 81, 1992.

[jrdahlman]

edstrick's explanation made me think of a question of spaceprobe construction:

Why even use filter wheels at all?

Now that 1000 x 1000 pixel sensors are so cheap, we can load probes with as many cameras as we want. Look how many the MERs have. So instead of possibly-sticky mechanical wheels, or prism arrangements (imagine a gigantic 8-prism for 8 filters!), why not just have an array of 8 separate cameras all pointing the same way, each with its own dedicated filter?

Granted, for landers or other close-up features the parallax would be unacceptable, but for planetary flyby/orbits, parallax would be too tiny to see. (Wouldn't it?) Then it could take pictures with ALL the filters all at the same time--no motion shift between them! And you wouldn't even have to worry about 8x the data coming back, because you could still transmit them sequentially, or even decide which filtered pictures are worth sending.

How come they're not being built this way now?

[paxdan]

edstrick's explanation made me think of a question of spaceprobe construction:

Why even use filter wheels at all?

Now that 1000 x 1000 pixel sensors are so cheap, we can load probes with as many cameras as we want. Look how many the MERs have. So instead of possibly-sticky mechanical wheels, or prism arrangements (imagine a gigantic 8-prism for 8 filters!), why not just have an array of 8 separate cameras all pointing the same way, each with its own dedicated filter?

Granted, for landers or other close-up features the parallax would be unacceptable, but for planetary flyby/orbits, parallax would be too tiny to see. (Wouldn't it?) Then it could take pictures with ALL the filters all at the same time--no motion shift between them! And  you wouldn't even have to worry about  8x the data coming back, because you could still transmit them sequentially, or even decide which filtered pictures are worth sending.

How come they're not being built this way now?

Because the cost of the sensor isn't the limiting factor, it is the size and weight of the camera(s). Mass and volume constraints are very tight on space craft. A filter wheel is a far more elegent solution to capturing a variety of wavelengths than duplicating the entire camera. A filter wheel weighs very little and occupies very little space, far far less than duplicating the sensor, optics and camera body multiple times.

The problem of motion shift is an interesting one for orbiters/flyby craft. There has been recent discussion regarding the use of 'sport mode' on the MER PANCAM. This cuts the interval between frames to 3 seconds from 10-20. While the interval between frames for Cassini is longer, one wonders wheather the use of subframe images or better routines will be able to squeeze a higher frame rate from the camera.

It is important to remember that spacecraft are primarily scientific instruments. Thus when spacecraft are designed, and choices made between returning scientifically calibrated data or pretty pictures the former must take priority and thus we should be thankfull that the latter is so often acheived as well.

[JRehling]

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.

Great stuff.

The area in the left image is an example of terrain where bright ice was seen to vary in IR brightness even though it was fairly uniform in visible. That might mean that it's impossible to interpolate/extrapolate between 756nm (near IR, actually just on the fringe of the visible spectrum) and 650nm (more of a central "red"). The differences between the "whites" can be seen vaguely in your image, and might not in "true" color. But beautiful stuff, and probably otherwise very on target, IMO.

[Decepticon]

Exploitcorporations Did you find any global images that have not been seen yet?

[Exploitcorporati...]

Exploitcorporations Did you find any global images that have not been seen yet?

No, that mine has been exhausted, and was unfortunately not very deep. Partial 1-4km scale mosaics were obtained on G1, E4, E6, G7, E12, E14, I25 and one nice full-frame view on E17. More distant, full-globe images were obtained on G2, C9, C10, G28, and I33. Eclipse and very distant plume search view were taken on C10 and C20. The exquisite color work seen here by Ted Stryk, Bjorn Jonsson, Mattias Malmer, and others covering these views, particularly the E14 mosaic, are as good as it gets.

[DDAVIS]

Has anyone here cleaned up this picture? It one of my favorite images of Europa http://photojournal.jpl.nasa.gov/jpeg/PIA02528.jpg

Yup. Here is my initial attempt at this, which has been crudely colorized as well.

Don

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[Decepticon]

Nice!

[tedstryk]

Yeah, global color views and what the Cassini folks would call "Kodak Moments" were some of the big losers to Galileo's woes.

C10 images were more intended to study the rings, but Europa happened to be there, and kind of stole the show. It is a pretty set, but is black and white.



The two C20 images are so underexposed and extremely noisy, making them almost unrecognizable. Here is the best I have been able to pull from them.

[mgrodzki]

Yup. Here is my initial attempt at this, which has been crudely colorized as well.

Don

that is one awesome image of europa. for one of the most important bodies in the solar system… its shocking how few there are of this. #59 that is.

[remcook]

pretty map
http://news.bbc.co.uk/1/hi/sci/tech/6454039.stm

[PhilHorzempa]

The remarkable mosaics on the "Ganymede Revisited" thread got me thinking
about what might have been done for Galileo's Europa images on UMSF.
Lo and behold, there are earlier threads that included Europa mosaics. I say that
in the past tense because if you check out threads such as "Europa's Northern
Plains" and "Thera, Thrace, and Agneor Linea," then you will see that most, if not
all, of those mosaics are gone. It appears that the host for those data may no longer
exist, as such.

Can the members of UMSF re-create some of those Europa mosaics, which, from
the comments in those threads, were impressive?


Another Phil

[tedstryk]

Exploitcorporations has a spectacular collection on her Flickr site.

[Exploitcorporati...]

Hi Phil. All of those mosaics are in reduced-scale form at the flickr link at the bottom of my posts now...the site they had been linked to was deleted in my long absence last summer. I will eventually have those dead links connected to the flickr page, and hopefully get those images up there at full size once I scrape enough change out of my sofa to get a paid account.

[tty]

It appears that the host for those data may no longer
exist, as such.

As always in such cases: try the Wayback Machine (http://www.archive.org/index.php). At least one of the mosaics is available there.

[MarcF]

Here is one mosaic I really like and which I found only recently:

http://berlinadmin.dlr.de/HofW/nr/080/

Just 4 pictures assembled out of 30 taken during E19 in order to search for plumes.
Anyway, the perspective is amazing !
Marc.

[ugordan]

It's so nice to see mosaic footprints aligning nicely in Galileo imagery. That's what a scan platform and a fast camera gives you, I guess. Were it not for forced JPEG-like compression, the imagery would have been very crisp. The PSF of the Galileo SSI camera was pretty tight and images could be sharpened nicely. Galileo may have had a lower resolution CCD than Cassini, but the image crispness more than compensated for it. It really was a capable camera...

All the more reasons to regard the loss of the HGA as catastrophic.

[tedstryk]

Take a look at the raws from the lunar flybys. Gives you an idea of what could have been done had the antenna opened.

[MarcF]

May be this is not really new, but I just found it on the USGS planetary nomenclature site:
The big albedo features (bright plains and mottled terrains) on Europa have now official names (as Regio):


Name (LAT / LON / DIAM) :

Annwn Regio (20.0 / 320.0 / 2,300)

Argadnel Regio (-14.6 / 208.5 / 1,900)

Balgatan Regio (-50.0 / 30.0 / 2,500)

Dyfed Regio (10.0 / 250.0 / 1,750)

Falga Regio (30.0 / 210.0 / 2,500)

Moytura Regio (-50.0 / 294.3 / 483)

Powys Regio (0.0 / 145.0 / 2,000)

Tara Regio (-10.0 / 75.0 / 1,780)

I already knew about Argadnel and Moytura Regiones, but the other names seem to be quite new.
Some new crater and Lineae names have also been assigned.
Marc.

[ugordan]

Here's my version of the Europa 14ESGLOCOL01 mosaic using all color that was available. A lot of synthetic color at places, the terminator is pretty much only green filter data. Too bad about that huge gouge of missing data at upper left.


Color balance was roughly based on a Cassini RGB image showing pretty much an identical vantage point. Still slightly exaggerated colors, I think.

[CAP-Team]

Nice work!

[tedstryk]

Good work. I primarily stole from the G-1 mosaic to fill that nasty gap.

[ElkGroveDan]

That is a fantastic image. It sure emphasizes the "bloodshot eye" appearance of Europa (but I have to go from memory as it has been years since I went to a college fraternity party).

[nprev]

Really amazing work, G. The long troughs near the terminator really stand out in this view; don't recall seeing them as well in previous global mosaics.

[DrShank]

Really amazing work, G. The long troughs near the terminator really stand out in this view; don't recall seeing them as well in previous global mosaics.

the long troughs are part of a global pattern. several other troughs elsewhere form part of a set of two giant circles
on opposite sides of the moon. They actually match the stress patterns produced if you rotate Europa's floating ice shell
almost 90 degrees (aka polar wander).
check out the story at http://www.lpi.usra.edu/science/schenk/europaCropCircles/

paul

[machi]

Merry Christmas to everyone on the site!

(It's one of the highest resolution mosaic of Europa from Galileo, with resolution around 10 m/pix horizontal. Artificially colorised by average color of this regio (Lat. -8.55;Long. 215))

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[Decepticon]

^ That just made my day! Amazing view.

[algorimancer]

That is really nice. I especially like that sharp boundary between white above and dark below on the big fracture a little above center. I suspect the dark material must be sulfur compounds from Io settling on low areas of the surface, but it almost looks stratigraphic in that spot.

[machi]

Little preview from Europa.
High resolution mosaic of Conamara Chaos (~12 m/pix). Image is colorized from lower resolution images (~200 m/pix)
This image is reduced in size (2×).

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[elakdawalla]

Wonderful!! I think this is the first time I have seen this mosaic without it being horribly saturated, and the color makes it even better. I love the pieces of ridges crossing rafts.

Every fine image from a Galilean moon that I see at UMSF makes me want to go back to Jupiter and do the Galileo mission properly, with a working HGA...

[nprev]

(Sigh)...me too, Emily, me too. Sure wish we'd see something like that proposed in the RFP cycles...could probably do it on a less-than-Flagship budget these days.

[stevesliva]

It would also be nice to have a few 10s of kilos of Pu-238.

[DrShank]

Wonderful!! I think this is the first time I have seen this mosaic without it being horribly saturated, and the color makes it even better. I love the pieces of ridges crossing rafts.

Every fine image from a Galilean moon that I see at UMSF makes me want to go back to Jupiter and do the Galileo mission properly, with a working HGA...

Nice work! here is my version from the Atlas of Galilean Satellites for comparison. scaled by 50% for upload

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[elakdawalla]

OK, that's pretty super too. I need to get my hands on a copy of that book. The guy running the booth at DPS/EPSC had packed up his display copies before I had a chance to bat my eyelashes at him and wheedle it out of him. (I did have success with that tactic at the Springer booth, got me the display copy of Michael Carroll's latest book, Drifting on Alien Winds. I've *really* been enjoying that one.)

[antipode]

Wow - there are some substantial shadows there. How much vertical relief are we looking at on the edge of some of those....islands....rafts....Europabergs?

P

[machi]

I can help with this little bit
Actually my new blog entry (planned) is about stereoscopic images from this mosaic. That mosaic has "only" supporting role (but at the end, it is better than I expected).
I think, that some cliffs are significantly more than 100 meters high and some are nearly vertical.
Little preview:

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[stevesliva]

Every fine image from a Galilean moon that I see at UMSF makes me want to go back to Jupiter and do the Galileo mission properly, with a working HGA...

To some extent there is hope for that with the flyby-oriented mission mentioned here:
http://futureplanets.blogspot.com/2011/10/...ew-options.html
... a relatively heartening post. Interesting idea to split the super-rad-hard science that must be on an orbiter from the less-rad-hard science that can be on a Galileo-like flyby tour. Seems like a reasonable economy and not a false one.

Also... fantastic mosaics!