Innovative UAV-to-satellite communication link concepts using adaptive optics

Covertness of an Unmanned Aerial Vehicle (UAV) could be enhanced by replacing the radio frequency communications link with a laser communication (lasercomm) link.  But, in order to have a large enough field of regard, the lasercomm system requires a heavy mechanical gimbal mounted in a dome.  This produces a turbulent aero-optics boundary layer that induces mechanical jitter and distorts the lasercomm beam with high spatial and temporal frequency aberrations.  A conventional adaptive optics (AO) system designed to correct the aberrations would have a deformable mirror (DM) with hundreds of moving actuators, greatly impacting size, weight, and power (SWAP) requirements.  This effort will investigate replacing the gimbal and dome with a wide angle steering system (WASS) based on a volume Bragg grating and liquid crystal spatial light modulators (LCSLM).  Without the dome, the aero-optics boundary layer will be inviscid, greatly reducing the amplitude and spatio-temporal frequencies of the aberrations.  The mechanical DM could then be replaced by another LCSLM, further decreasing SWAP.  This effort will include a preliminary design of the WASS and LCSLM AO systems, a prediction of the aero-optics flow-fields, and a wave-optics prediction of the cumulative distribution function of the lasercomm received power. BENEFIT: For any airborne optical system, replacing the gimbal and dome with a Wide Angle Steering System (WASS) could greatly reduce the size, weight, and power (SWAP) requirements and produce a much more benign aero-optical boundary layer.  This would mitigate the aero-mechanical jitter problem and reduce the amplitude and spatio-temporal frequency requirements of the adaptive optics (AO) system enough so that the mechanical deformable mirror (DM) could be replaced by a liquid crystal spatial light modulator (LCSLM), further decreasing SWAP and also increasing reliability.  The LCSLM AO system investigated in this effort could also be beneficial in other applications that do not require a very high temporal frequency.  A satellite based optical system might also benefit from the lower SWAP of a WASS relative to a mechanical gimbal.  In addition to the optical system design, significant capabilities will be added to one of the governments standard wave optics codes and it will be used to predict performance of both conventional systems and the new designs.