[X] My Assistant

[Juramike]

Flyby page is up (mission description not yet posted): http://saturn.jpl.nasa.gov/mission/flybys/titan20090505/

[ngunn]

Mention of atmospheric emissions sent me off to do some reading on that as well. As a complete beginner I found this article useful:

http://astroprofspage.com/archives/445

It seems that on Earth sunlight is the main source of energy for natural airglow, with cosmic rays providing a smaller but still considerable contribution. In Titan's case one might expect that situation to be reversed, perhaps enormously reversed with a big Cerenkov component, but I'm only guessing there. How bright is it relative to ambient starlight? I haven't a clue, but maybe it could dominate after all. A comparative set of Rhea eclipse images (when Titan is out of the way) would be interesting. I wonder whether that will figure in future plans, or if indeed existing Rhea images (at their full dynamic range) could come into play here. Where was Titan when those shots were taken? Questions, questions.

I think I'll give up at this point (sighs of relief all round) and wait to see what the professionals come up with. I've learned enough to know that their task is not straightforward.
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EDIT: a terrestrial comparison, QUOTE from here http://www.albany.edu/faculty/rgk/atm101/airglow.htm (my highlighting):

Airglow is commonly divide into:
Dayglow (when entire atmosphere is illuminated by the Sun) is the brightest airglow due to the importance of RESONANT and FLUORESCENT processes (see below) but it is overwhelmed by direct and scattered sunlight
Twilightglow (when only the upper atmosphere is illuminated) is the most readily observable airglow from the ground since the observer is in darkness (and Rayleigh scattering of sunlight by the dense lower atmosphere is absent) while the airglow region of upper atmosphere is still illuminated
Nightglow (when entire atmosphere is in darkness) is not as bright as dayglow since CHEMILUMINESCENCE (see below) is the dominant process; however contributes more light than starlight to the total luminosity of the night sky