Rotating UFOs to aim at target

So I'm trying to get a group of UFOs flying in formation, which closes in on a target and have it surrounded. I need them to turn their beam of destruction (which is now pointing downwards) to a target on the ground and unleash hell.

If the UFOs are controlled by a joystick that only allows input on the X and Y axis wrt themself, what should the values be respectively? The height above ground and radius of their formation is known. ![alt text][1]

http://i.imgur.com/VPI3mJz.jpg [1]: /storage/temp/56229-2015-10-15-16-57-37-448.jpg