This is why the NK Bright Star satellite has not been shot down
US Defense analysts are not certain, but suspect that the device may be a dirty bomb of sorts. They suspect that it may contain nuclear material, not a nuclear weapon, but radioactive material.
To shoot the device down would spread whatever it contains. So all that can be done is to wait and see what happens. If the US acts and the device contaminates a thrid party nation the reactiob is unpredictable. At this point not touching it leaves ownership of the outcome solely upon DPRK.