Thank you! It seems wikipedia confirms what you are saying. Sadly the article it references is no longer available, so i can’t dig into it. But it sounds 1/270 is for the requirement for overall mission while the ascent and descent phases have 1/500 apportioned to them each.
Was trying to put this 1/500 number into perspective for myself. It sounds like it is rougly similar to the mortality of having appendicites. [1]
