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DSCOVR
scalbers
post Jan 3 2018, 09:49 PM
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Here is our "DSCOVR Transcendance" poster from AGU, highlighting Blueturn and the Simulated Weather Imagery. The authors included Michael Boccara, Jay Herman, and Zoltan Toth.

https://agu.confex.com/agu/fm17/meetingapp.cgi/Paper/232523

https://agu.confex.com/agu/fm17/mediafile/H...anscendance.pdf


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scalbers
post Mar 1 2018, 12:20 AM
Post #152


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I've recently made some fixes to the handling of Rayleigh scattering in making simulated Earth images. This makes the simulated blue sky (over ocean areas) somewhat darker than previously. As a result less color adjustment to the DSCOVR web images is need to make a match. Hopefully this is now a more realistic color and contrast.

Attached Image


The left is simulated (ray-traced) from global 3-D weather and land surface data, right is a DSCOVR/EPIC image at the same time. In general my simulations come up a little short on the brightest cloud reflectance values. This can be partially addressed by adjusting the anisotropic reflectance factor for the bright cloud tops.


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scalbers
post Mar 3 2018, 06:09 PM
Post #153


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Also for comparison, here is an image constructed from the DSCOVR calibrated counts data, converted to reflectance and then using my color processing algorithms to calculate the RGB values. The blue color looks somewhat brighter than in the DSCOVR web page images. This should be close to a true color / contrast astronaut view. The brightness is set to minimize clipping of the brightest white clouds. There's really an interesting variety of whiteness to the clouds with the deepest most opaque ones near the center being the brightest. Some additional processing would be needed to register the individual narrowband image locations better, considering the Earth's rotation.

Attached Image


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scalbers
post Jul 20 2018, 07:23 PM
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With some further adjustments I get this comparison that is hopefully a bit closer, including a slightly darker blue over the oceans. The land is now brighter relative to the scattered light in the atmosphere.

The ocean/sky blue is brighter in the image one post above for perhaps multiple reasons. One way to characterize this gap is to note that the simulated 551nm reflectance in the darkest ocean areas is about 4.4% compared with 5.0% observed. The blue channel and color saturation are also higher in the above post. The same dark ocean areas are observed to have ~12.4% reflectance at 443nm and the simulation has a lower value. This gap can be bridged by considering reflected sunlight from beneath the water surface, and also checking the reflected skylight from the surface.

Attached Image


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scalbers
post Jul 21 2018, 04:40 PM
Post #155


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With this refinement to increase the reflected light from beneath the water surface we can see the comparison below.

Attached Image


The simulated image on the left is a closer match to the observed color processed version in post #153. The image on the right is from the DSCOVR website with an empirical color adjustment.


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scalbers
post Sep 3 2018, 01:14 PM
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To help with rendering the Earth, a guideline I've come across is that the chromaticity of the blue sky (due to Rayleigh scattering) should be about x=0.23 and y=0.23. This helps quantify the relative values of RGB in the clear sky portion of Earth images. This is assuming that the standard CIE color matching functions are correct in describing how this color is perceived.

A relation that I hadn't before known is that this "Rayleigh Blue" color is about the same color a star would have with an infinite (or very high) blackbody temperature. Thus on an imaginary planet orbiting a very early type O star a water cloud there would be about the same color as a haze free blue sky on Earth, instead of white.


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scalbers
post Aug 12 2019, 10:14 PM
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DSCOVR has been in safe mode since June 27th: https://spacenews.com/dscovr-spacecraft-in-safe-mode/

I wonder if an archive of L1B files is stil available in NetCDF or HDF format?


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scalbers
post Oct 3 2019, 09:46 PM
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A fix is being worked on: https://spacenews.com/software-fix-planned-...restore-dscovr/


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scalbers
post Apr 1 2020, 10:07 PM
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DSCOVR has been back in operation now, already for a few weeks. The color processing for the web images is also now more accurate than it was before the hiatus.


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bkellysky
post Apr 4 2020, 11:27 AM
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QUOTE (scalbers @ Apr 1 2020, 06:07 PM) *
DSCOVR has been back in operation now, already for a few weeks. The color processing for the web images is also now more accurate than it was before the hiatus.


Thank you for your reports on DSCOVR!
In case anyone needs a link to the whole-earth photos: https://epic.gsfc.nasa.gov/
bob k
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scalbers
post Apr 23 2020, 10:02 PM
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Sounds good bkellysky! I'm attaching a relatively recent comparison (still before the hiatus) with a simulated Earth image from real-time (independent) 3D cloud / aerosol fields with land surface data. DSCOVR is on the right. This version underestimates the dust aerosols off the West Africa coast near the right limb, though I'm presently testing some improvements.

Attached Image


More info is here: http://stevealbers.net/albers/allsky/outerspace.html


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threadworm
post Jan 21 2022, 04:59 PM
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DSCOVR also caught the start of the eruption:

https://epic.gsfc.nasa.gov/archive/natural/...20115042159.png

Attached Image


Taken at 04:21:59 GMT
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Michael Boccara
post Oct 29 2022, 01:44 PM
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This is October, 25th, 2022, and the time is 11:19UTC.

Two cosmic events are happening at the same time, involving the 3 main celestial bodies. In one sentence:
The Sun is smiling while looking at the Moon cast its shadow onto the Earth.

Two pictures shot at the exact same moment:
1. Left: Almost total sun eclipse over Russia. See the Earth "eaten" at the North-East. Picture by DSCOVR satellite around L1. What the Sun sees of us...
2. Right: a smile draw on the Sun surface by its coronal holes. As if it liked the show smile.gif. Picture by NASA SDO satellite, also on L1, but looking the other way.
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bkellysky
post Oct 27 2023, 03:19 PM
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DSCOVR image including the darkness over western North America from the annular eclipse of Oct 14.
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john_s
post Oct 27 2023, 03:28 PM
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Nice image, but something must be off with the colors- the shadow looks brown but should be neutrally colored, as the moon will block all wavelengths equally.

John
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