The Martian Sky |
The Martian Sky |
Oct 11 2009, 06:41 PM
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IMG to PNG GOD Group: Moderator Posts: 2254 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
I have been attempting to make computer generated images of the Martian atmosphere, both as seen from the surface and from space. To check the results I have been looking for spacecraft images to use as ground truth. I have found lots of images - by far the best ones I have found are from UMSF in this thread: http://www.unmannedspaceflight.com/index.php?showtopic=3324
However, I'm always looking for more ;-). So if anyone knows of more and/or better images I'm interested in them. What would be best are mosaics showing the sky from the horizon (with the horizon/surface visible) and towards the zenith. The sky varies a lot because of variable amount of dust but the general impression I get is that the sky is bright near the horizon (usually brighter than the surface) but gets much darker higher in the sky. There is probably a fairly large, bright area in the sky near the sun, possibly less reddish (lower R/B ratio) than parts of the sky farther from the sun. I'm already getting fairly interesting results, this one has a field of view of 90 degrees: (needless to say this one is 'overexposed' near the horizon; dynamic range is sometimes a problem) The problem is that even though this may not be bad the limb currently appears far too bright as seen from space : This shows that my atmospheric model is erroneous in some way - I suspect that as seen from the surface the Martian sky is darker high above the horizon than I have been assuming. |
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Sep 4 2021, 06:31 PM
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Senior Member Group: Members Posts: 1669 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Thanks JohnVV. Revisiting this a bit I made a sequence of frames with a Monte Carlo ray-tracing algorithm located here:
https://stevealbers.net/ast/mars/mc/ An HTML5 viewer to see an example 16-bit frame with various brightness settings can be found here: http://stevealbers.net/ast/mars/mc/briloop...ghtness_36.html It still needs some work on the blue sunrise. In fact the blue color surrounding the sun should actually be present all day long in addition to sunrise/set. Exactly how strong the blue color saturation is appears open to some interpretation. Figure 10 of this paper gives a modestly blue chromaticity near sunset. Another more recent paper has some interesting discussion. It's a bit unclear how to translate this into the optical properties I'm looking for, so it's a bit of trial and error to simulate close to observed chromaticities. -------------------- Steve [ my home page and planetary maps page ]
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