There is a configuration file that contains the distances for detection, weapon data, and pretty all things related to gamplay. In order to not get my game spoiled I have just roughly taken a look to know what's inside, but I closed it after 20 seconds. I think if I knew everything I would not play the game anymore. And that would be a pitty
If you are interested in the game I advice you NOT to take a look, the mania to 'know' everything usually does no good...Sigmund Freud would say: those are infantile dreams, he didn't know about VR...
Except of course if you only mod the game. But then, this file should be the first one taking your attention, don't you think?
If the moon/sun plays any role then it would be there inside, or in the 'environment' files (less likely, because they rather establish the grafics rather than gameplay sim).