WAVE-FRONT CORRECTION BY ONE OR MORE SYNTHETIC BEACONS

Adaptive optics has been used in a cooperative mode to measure the pha se distortion of the light from a star and to correct its image with a deformable mirror. A wave-front sensor in the adaptive-optics system that measures the phase aberrations requires that an object be fairly bright for accurate performance of the measurement. The use of synthet ic beacons provides a means of correcting the images of objects that a re too dim to allow one to use their light to provide correction in a cooperative mode. Synthetic beacons at a finite distance do not provid e a perfect correction in imaging an object at a greater distance. The error in making a correction with one or more beacons is analyzed. An alytical expressions that can be used to determine performance in a va riety of geometries, with various beacon altitudes and numbers, are de rived. This analysis is applied to 60-cm and 4-m systems.