How to use radar sensor?

I wants to create space draughts game. Its same as original 2-dimention game, but any gamer have 64 spheres and game space is cube divided on 8 cells by the width, height and depth - 512 cells at summ. When enemy sphere will seen near any our spheres,we must calculate direction and distance from enemy to nearest unit,drive unit behind enemy on all dimensions and destroy that enemy. But I cant use a radar sensor: when I trying to catch it,I saw warning:“btCollisionDispatcher::needsCollision: static-static collision!”, and nothing expect that.There are my python script for radar:

import GameLogic
co = GameLogic.getCurrentController()
rad = co.getSensor("sensor2")
if rad.isPositive():
	print dir(rad)

Does somebody know, how to use this sensor?