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Global True Color View Of Venus?
elakdawalla
post Aug 8 2005, 06:53 PM
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I'm creating a website with views of the worlds of the solar system, to scale with each other (it'll march up and down the few orders of magnitude necessary), and I am having a terrible time finding a global view of Venus to include in it that fits the criteria I'm trying to apply. To the extent possible, I am searching for:

- Full-disk, global view
- Minimum phase angle available
- Approximate true color, as would be perceived by a human observing the globe from space

For Venus, the only global views I am finding are either based on Magellan data (radar views, nothing like what a human would see) or are colorized ultraviolet views (which greatly overemphasize the visibility of cloud patterns in the Venusian atmosphere). I've seen the lovely partial global view of Venus on Don Mitchell's website -- that's the sort of thing I'm looking for, but I need a full disk. Does anybody have any suggestions? Anybody done any work with Mariner 10 or Galileo data that produces a nice, realistic view?


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4th rock from th...
post Dec 29 2008, 01:08 PM
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Hi all,

I've updated my webpage with some Venus Express images processed in approximate real color.

The images seem to show the Venusian atmosphere extending from the limb with a bluish color. The general tone of the planet is yellowish, in accordance to similar processing I've done with Mariner 10 images, available on this site. The brightest clouds are bluish, given that they reflect strongly on the UV parts of the spectrum.

RGB channels were computed from NIR1, VIS and UV images using the following averages:

Red = 0.3 x NIR1 + 0.7 x VIS = 0.3 x 965 + 0.7 x 513 = 649
Green = VIS = 513
Blue = 0.5 x VIS + 0.5 x UV = 0.5 x 513 + 0.5 x 365 = 439

Here's one image, you can see more at http://www.astrosurf.com/nunes/explor/explor_vex.htm



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ugordan
post Jun 1 2009, 06:48 PM
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I've been messing around with the MESSENGER calibrated data and even though it's not a complete global view, I thought I'd share it here. From the filter choice standpoint, it's the closest we get to a RGB image for the time being. I already posted a few of those in the MESSENGER PDS threads, but those were quick-n-dirty versions.

Below is the familiar inbound view by the wide-angle camera, but this time I approached it somewhat differently. Instead of the typical E/D/C "red/green/blue" filter combo, I used E/D/F. Even though the "F" filter is labeled as violet, at 430 nm central wavelength it's actually much closer to the peak sensitivity of the blue light-sensitive cones in the human eye (437 nm). The "C" filter is shifted way too much toward green at 480 nm and also much more narrowband. Venus composites using the "blue" filter as a result fail to capture the bright clouds that reflect strongly in the UV, while the "F" filter does exactly that while still being inside human vision boundaries, i.e. not being UV.

I used the ground calibration tables when calibrating the data as the inflight-derived results look inconsistent across filters to me. Next, I took the central filter wavelengths and compared them to the sRGB colospace central wavelengths. I calculated approximate channel mixes to bring the "average" wavelength in all 3 RGB channels to sRGB, this is what I used:

red = 0.72*E + 0.28*D
grn = 0.93*D + 0.07*F
blu = 0.73*F + 0.27*D

Finally, I boosted saturation by +15 to compensate for a slight loss of saturation by above mixing.

Here is the resulting composite:
Attached Image


It looks as it's in the same ballpark as some other versions here. This one is not gamma-corrected because absolutely all contrast would be washed out and you'd end up with a shiny white billiard ball.

Here's a high-pass enhancement to bring the clouds out a bit:
Attached Image


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4th rock from th...
post Jun 2 2009, 09:55 AM
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QUOTE (ugordan @ Jun 1 2009, 06:48 PM) *
... I calculated approximate channel mixes to bring the "average" wavelength in all 3 RGB channels to sRGB...
...This one is not gamma-corrected because absolutely all contrast would be washed out and you'd end up with a shiny white billiard ball.
....


Nice results. I think that the channel mixing to average center wavelenght works very very well and can be used with almost any filter set. I'm not shure it saturation suffers that much, because that would have more to do with each filter bandwidth. Nevertheless, results are consistent. I think that you could include a gamma corrected version, because that would show exactly why the details are dificult to see at the telescope. It would also be closer to what we might see if in orbit of the planet.


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ugordan
post Jun 2 2009, 10:15 AM
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QUOTE (4th rock from the sun @ Jun 2 2009, 11:55 AM) *
I think that you could include a gamma corrected version, because that would show exactly why the details are dificult to see at the telescope. It would also be closer to what we might see if in orbit of the planet.

Well, you asked for it:
Attached Image


This was done on the 8 bit PNG above, not the 16 bit one I worked with as I'm at work now, but this only induces a slightly higher noise near the terminator. I continue to be amazed at just how sharply defined the planet's limb is. It really looks like someone put a solid ball in space - no limb brightening or other Rayleigh scattering effects.


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Posts in this topic
- elakdawalla   Global True Color View Of Venus?   Aug 8 2005, 06:53 PM
- - BruceMoomaw   You might look into the images from Pioneer 12...   Aug 8 2005, 06:58 PM
|- - tedstryk   Yes, but I don't think it took multiband image...   Aug 8 2005, 10:09 PM
- - JRehling   QUOTE (elakdawalla @ Aug 8 2005, 11:53 AM)I...   Aug 8 2005, 09:02 PM
- - 4th rock from the sun   My best attempts, using Mariner 10 "clear...   Aug 8 2005, 11:48 PM
|- - elakdawalla   QUOTE (4th rock from the sun @ Aug 8 2005, 04...   Aug 10 2005, 03:39 AM
- - 4th rock from the sun   Ok, here's a Venus atmospheric profile. It s...   Aug 8 2005, 11:55 PM
- - 4th rock from the sun   Check my page http://www.astrosurf.com/nunes/explo...   Aug 10 2005, 12:44 PM
- - 4th rock from the sun   OK, here's all the data I have. This atmosph...   Aug 10 2005, 07:10 PM
- - planet_guy   If you are interested in the surface stuff done by...   Aug 25 2005, 01:17 PM
|- - algorimancer   QUOTE (planet_guy @ Aug 25 2005, 08:17 AM)If ...   Aug 26 2005, 01:09 PM
|- - tedstryk   QUOTE (planet_guy @ Aug 25 2005, 01:17 PM)If ...   Aug 26 2005, 02:00 PM
- - planet_guy   well the 16km/pix are using the 'holes' t...   Aug 26 2005, 03:18 PM
|- - tedstryk   QUOTE (planet_guy @ Aug 26 2005, 03:18 PM)wel...   Aug 26 2005, 03:25 PM
|- - JRehling   QUOTE (tedstryk @ Aug 26 2005, 08:25 AM)Sound...   Aug 26 2005, 03:50 PM
- - planet_guy   trust me.. I'm also hoping the predictions are...   Aug 26 2005, 03:28 PM
- - BruceMoomaw   I promised fully 2 months back to dig up whatever ...   Aug 29 2005, 12:39 AM
- - Tayfun Íner   It is unbelievable that Venus is the nearest plane...   Dec 4 2005, 06:41 PM
|- - JRehling   QUOTE (Tayfun Íner @ Dec 4 2005, 10:41 AM)It ...   Dec 5 2005, 02:03 AM
|- - DonPMitchell   There is a spectral albedo for Venus. That can be...   May 5 2006, 08:49 PM
- - JRehling   QUOTE (elakdawalla @ Aug 8 2005, 11:53 AM...   Oct 12 2007, 10:32 PM
- - scalbers   Well, I guess this wouldn't be true color, yet...   Oct 12 2007, 10:52 PM
- - Gladstoner   .   Jan 4 2008, 09:05 AM
- - 4th rock from the sun   Hi all, I've updated my webpage with some Ven...   Dec 29 2008, 01:08 PM
|- - ugordan   I've been messing around with the MESSENGER ca...   Jun 1 2009, 06:48 PM
|- - 4th rock from the sun   QUOTE (ugordan @ Jun 1 2009, 06:48 PM) .....   Jun 2 2009, 09:55 AM
|- - ugordan   QUOTE (4th rock from the sun @ Jun 2 2009, 11...   Jun 2 2009, 10:15 AM
- - Stu   Absolutely beautiful images, thanks for posting th...   Jun 1 2009, 08:48 PM
|- - ugordan   Sure, no problem at all, Stu. Glad you like them.   Jun 1 2009, 09:08 PM
- - Stu   Wow, there really would be b****r all to see if yo...   Jun 2 2009, 10:35 AM
|- - ugordan   Yep, and every time I see a montage of all solar s...   Jun 2 2009, 10:43 AM
|- - tedstryk   QUOTE (ugordan @ Jun 2 2009, 10:43 AM) Ye...   Jun 4 2009, 09:42 PM
||- - ngunn   QUOTE (tedstryk @ Jun 4 2009, 10:42 PM) c...   Jun 4 2009, 10:18 PM
|- - Stu   QUOTE (ugordan @ Jun 2 2009, 11:43 AM) Ye...   Jun 4 2009, 11:21 PM
|- - tedstryk   QUOTE (Stu @ Jun 5 2009, 12:21 AM) Every ...   Jun 5 2009, 10:21 AM
- - Juramike   Personally, I don't like the wavelength limita...   Jun 5 2009, 11:08 AM
|- - tedstryk   I would say that there is a difference between fal...   Jun 5 2009, 01:51 PM
- - Stu   The problem I encounter is that editors want to us...   Jun 5 2009, 01:58 PM
|- - tedstryk   I agree, but I still think that showing the Venusi...   Jun 5 2009, 04:41 PM
- - Stu   It's this image I have had to fight to stop ed...   Jun 5 2009, 05:40 PM
|- - tedstryk   Not only is the color bad, but that is a Mariner 1...   Jun 5 2009, 05:44 PM
- - Stu   Okay, but you get the idea, right? Editors can be ...   Jun 5 2009, 05:52 PM
|- - tedstryk   Yes, I get the idea. However, to me, the fact tha...   Jun 6 2009, 10:16 AM
- - brellis   When's Google Venus gonna be up and running?   Jun 5 2009, 08:42 PM
- - scalbers   Is this web page with a Venus image showing some r...   Oct 15 2010, 09:12 PM
|- - CJSF   QUOTE (scalbers @ Oct 15 2010, 05:12 PM) ...   Oct 16 2010, 12:26 AM
|- - scalbers   QUOTE (CJSF @ Oct 16 2010, 12:26 AM) I ag...   Oct 16 2010, 05:53 PM
|- - ugordan   It's not merely about color, it's about co...   Oct 16 2010, 06:01 PM
- - machi   It looks like old UV image from Pioneer Venus. I ...   Oct 15 2010, 09:26 PM
- - 4th rock from the sun   Here's my Pioneer Venus image galery: http://w...   Oct 16 2010, 03:33 PM
- - Phil Stooke   Nice set of pictures! The last image on your ...   Oct 16 2010, 04:18 PM
- - scalbers   Yes indeed the actual contrast is much more subtle...   Oct 16 2010, 06:06 PM
|- - 4th rock from the sun   QUOTE (scalbers @ Oct 16 2010, 07:06 PM) ...   Oct 17 2010, 01:26 PM
|- - scalbers   QUOTE (4th rock from the sun @ Oct 17 2010, 0...   Oct 17 2010, 08:59 PM
- - EDG   Has anyone actually tried to make a true-colour ma...   Oct 17 2010, 12:52 AM
- - nprev   I don't know how you could ever make a 'tr...   Oct 17 2010, 01:37 AM
|- - EDG   QUOTE (nprev @ Oct 16 2010, 06:37 PM) I d...   Oct 17 2010, 07:02 PM
|- - tedstryk   How on earth would that be any less simulated than...   Oct 17 2010, 07:45 PM
|- - EDG   QUOTE (tedstryk @ Oct 17 2010, 11:45 AM) ...   Oct 17 2010, 09:20 PM
- - JohnVV   QUOTE Has anyone actually tried to make a true-col...   Oct 18 2010, 02:53 AM


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