And why must it land on only one part of the moon?
You forget that there is ALWAYS a location on the moon which you could land on - there is ALWAYS a spot in lunar dawn. As for your reliability arguements, you have failed to prove anything with your handwaving. You'll need to make more specific claims before we can make anything of them (specific as in NUMBERS. I don't care if the plan is always changing - the changes right now are minor. Do calculations based on its current state).