means? >> yes. mr. ledgerwood has worked very hard and he has shared with us via e-mail his various thoughts. we appreciate them. i shared with him yesterday that we were certain we were right with the southern route rather than the northern route. the doppler shift, in very simple terms, is the way in which we see the effect of the slight movement of the satellite in space relative to the aircraft and from that proses, the compression or an expansion of the wave length, you can know whether the aircraft is moving closer or further away from the satellite. >> anderson, that would be exactly how we use doppler radar to determine that there is a tornado on the grown. the shift in the speed of the signal coming back or going forward is determined by the movement. it is like a train coming to you. if the train is coming to you, blowing its whistle, it is higher in pitch as it goes by