But it is a difficult task to scan the earth with a laser beam the size of a head of a needle, it would take alot of swingig and you would probably end up spending any gold money on doctors fees to fix your sore elbow from swinging the laser around.
read more about it at
http://www.nmp.csiro.au/ion.html
Estebans system was different and quite clever.
He modulated the laser output so the reflected wave is close to the modulated frequency, so you detect the reflected wave not the laser frequence.
rgds