Impact of the boundary layer on pointing and tracking in airborne free-space laser communication links

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes vita.Includes bibliographical references (p. 117-118).Free-space laser communication is a developing technology with enormous potential to revolutionize the way people communicate across the globe. Of specific interest are air-to-space lasercom links. Such a link experiences atmospheric scintillation, platform jitter, and boundary layer turbulence. This research investigated the tracking challenge using a focal plane array sensor with centroid and peak tracking algorithms. Also investigated was the use of a deformable mirror to recreate optical phase distortions from boundary layer turbulence. Experiments were conducted with realistic channel effects for multiple look angles between a subsonic aircraft at 29 kft and geosynchronous satellite. Performance was determined by power delivered to an optical fiber. The results show that the two tracking algorithms can differ by up to one decibel of fiber power, with centroid tracking generally performing best. Conclusions are highly dependent on aircraft and spacecraft parameters but point towards centroid tracking for maximizing received power. Keywords: Lasercom, FPA Tracking, Boundary Layer Disturbances, Deformable Mirror.by Ross Aaron Conrad.S.M