Bootstrap beacon creation technique for lower altitude and ground based targets

Abstract

The task of delivering a sufficient amount of laser energy to the ground based targets and the targets located at lower altitudes is of a high interest. The laser beam propagating through atmosphere is significantly degraded by the turbulence. As a result, the laser beam arriving at the target does not have sufficient amount of power. To overcome the degradations induced by atmospheric turbulence the artificial beacon for probing the atmospheric conditions is needed.The current techniques implementing a Rayleigh beacon at the target or at some intermediate distance between the transmitter and the target provide some means of improvement. In this work we extend our work on earlier proposed bootstrap technique in volving creating multiple beacons between the laser transmitter and the target. In the bootstrap technique, the light from each beacon is propagated back to the wavefront sensor located at the receiver. Signal from the wavefront sensor is processed to generate commands for the deformable mirror and the next beacon gets pre-compensated for the further distance.The process continues till the last beacon is created at the target. We have previously reported the results on implementation of the bootstrap techniques on ground based targets demonstrating noticeable improvement in the final laser beam power at the target. In this work we examine the possibility of using the bootstrap technique for cases when laser energy needs to be delivered over nearly horizontal propagation distances and at lower altitudes. The system performance is examined using both Hufnagel-Valley and HufnageVAndrewslPhillips models for structure constant C� characterizing the strength of the index of refraction fluctuation, and compared with the sceneries when the beacon is generated directly on the target or at some intermediate positions between the transmitter and the target.