Abstract: This paper reports progress in the use of laser beacons for compensating the images of faint objects using adaptive optics. The system describe is located at the USAF Phillips Laboratory's Starfire Optical Range near Albuquerque, New Mexico on a 1.5 m telescope. The adaptive optics system uses a 241 actuator continuous facesheet deformable mirror. A copper vapor laser beacon focused at 10 km range is used to sense higher-order distortions. A natural guide star is used for sensing full aperture tilt. The limiting factor for long exposure performance of the system is tracking - the correction of full aperture tilt. The main goal of the work reported here was to determine the performance of the tracking system under conditions of weak signal but good higher order compensation (similar to conditions encountered in laser beacon adaptive optics). Single axis rms track errors of approximately 20 milliarcsec were achieved for track signal levels equivalent to stars of 13$+th$/ magnitude. However, we cannot track stars fainter than 9 - 10$+th$/ magnitude because the laser induces very low level, long lived phosphorescence in the optical train. This appears to be a fundamental limitation for our system as it is presently configured.!9
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