A beam control system and method: The inventive system includes, an arrangement
for receiving a first beam of electromagnetic energy; measuring wavefront aberrations
in the first beam with a wavefront sensor; and removing global tilt from the measured
wavefront aberrations to provide higher order aberrations for beam control. In
the illustrative embodiment, the invention uses a traditional (quad-cell) Shack-Hartmann
wavefront sensor to measure wavefront aberrations. An adaptive optics processor
electronically removes the global tilt (angular jitter) from this measurement leaving
only the higher-order Zernike components. These higher-order aberrations are then
applied to wavefront control elements, such as deformable mirrors or spatial light
modulators that correct the tracker image and apply a conjugate distortion to the
wavefront of the outgoing HEL beam. A track error (angular jitter) component is
supplied by a separate fine track sensor. This jitter error is then applied by
the adaptive optics processor to a fast steering mirror, which corrects jitter
in the tracker image and applies a compensating distortion to the LOS of the HEL beam.