DSCOVR |
DSCOVR |
Jan 6 2006, 08:55 PM
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#101
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
ADMIN NOTE: Please note that this topic was unavoidably poltical before the 'No Politics' rule. Please restrict future comments to the mission/spacecraft/news updates etc.
WHAT'S NEW Robert L. Park Friday, 6 Jan 06 Washington, DC DEEP SPACE CLIMATE OBSERVATORY KILLED. http://bobpark.physics.umd.edu/index.html -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Mar 23 2016, 08:25 PM
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#102
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Senior Member Group: Members Posts: 1669 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
I'm continuing to think about the most realistic brightness/contrast adjustment for the DSCOVR imagery. One line of reasoning is that in green light the oceanic areas (with overlying atmosphere) should be about 12% reflectance. The brightest clouds would be about 100% reflectance. So that is a ratio of 8.5 in brightness and a gamma corrected ratio of 2.62. In other words, if the bright white clouds are 255 counts, the oceanic areas near the center of the image (though outside of sun glint) should be about 97 counts. This means I should try a greater contrast reduction for the DSCOVR imagery than I had done previously (in post #81). I have posed a question to the DSCOVR team somewhat along these lines.
It's also interesting to note that the brightest clouds are found near the center of the Earth. Near the limb they are paler looking. Some of this is related to there being more intervening atmosphere above the clouds with the more grazing path. However it also seems to be related to a reduction of backscattering when light hits the cloud at a glancing angle and/or on the side. This can be compared with limb darkening on other cloudy planets and moons in the Solar System. -------------------- Steve [ my home page and planetary maps page ]
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