re: synthesized color versus calibrated subtractive color
"average color of sunlight on Mars" - I love the way NASA handled the Viking data for some 25 years. Mars atmsohperic dust loading over time should long since have been pulled out of the Viking ground shots, but as it is...
Isn't the fast and dirty way to handle MER images simply to set the average Matian sky to a known value (D65 white)? This might compensate for dust loading and angle of incidence, albeit not thoroughly and particularly with respect to shadowing - that requires an intelligent filter.
I'd just label the images in the header, if not in a surround, so that everyone knows...
ep