Juno at Jupiter, mission events as they unfold Options

[nprev]

This topic will consist of discussion of Juno operations post-JOI until end of mission, currently anticipated in Feb 2018.

[Gerald]

Ah, yes, this could resolve the discrepancy. I've seen material from Earth's moon from less than a meter distance, and it looked perfectly grey. But it likely wasn't directly from the surface. If Moon's surface reddens from space weathering, then it should look reddish, consistent with the appearence of Moon in EFB01, after I've been following your advice to use Earth's clouds as white calibration targets. (One of the (large!) resulting processed EFB12 files here.) However, the color of the clouds aren't quite uniform, so this a compromise.
Since then I've applied the weights (0.74, 0.88, 1.0) for square-root encoded (r,g,b ). Stretching to red=1.0, this would correspond to (1.0, 1.19, 1.35) for square-root encoded (r,g,b ), or to about (1.0, 1.41, 1.83) for linearized (r,g,b ).

The CCD should behave close to linear with exposure time, according to subsection 4.1 of the JunoCam paper:

Linearity and full well were measured using integrating sphere images taken with a series of exposure times. This shows excellent linearity (r = 0.99) until the full well is reached at about 1872 DN (30,500 electrons), illustrated in Fig. 18.

[scalbers]

Nice to see your updated large Earth view. It is true the cloud colors can vary, especially with lower sun elevation angles and when viewing near the limb. For example it's OK for the clouds right at the terminator to be a bit on the red side. The bright high clouds would be the best reference. For these there are still some effects with atmospheric scattering and absorption, though intensities of various colors should shift by only a few percent.

What is most noticeable to me though is that the ocean areas (including the sun glint) surrounding Chile/Argentina appear to have a greenish cast. I think when color does appear in this situation it would be more orangeish. At the risk of going outside the bounds of this forum, there are lots of videos available showing Earth from various geometries illustrating this that reasonably match the geometry we're seeing with Juno.

Just for fun I made a subjective adjustment to your image that hopefully changes it in the right direction (lowering green by 14% in the GIMP in "shadowed" areas):



Looking more online, I can also see data about the moon being reddish, more so in the brighter highlands.

Ah, yes, this could resolve the discrepancy. I've seen material from Earth's moon from less than a meter distance, and it looked perfectly grey. But it likely wasn't directly from the surface. If Moon's surface reddens from space weathering, then it should look reddish, consistent with the appearence of Moon in EFB01, after I've been following your advice to use Earth's clouds as white calibration targets. (One of the (large!) resulting processed EFB12 files here.) However, the color of the clouds aren't quite uniform, so this a compromise.
Since then I've applied the weights (0.74, 0.88, 1.0) for square-root encoded (r,g,b ). Stretching to red=1.0, this would correspond to (1.0, 1.19, 1.35) for square-root encoded (r,g,b ), or to about (1.0, 1.41, 1.83) for linearized (r,g,b ).