Adaptive optics system for the observation of terrestrial point-like sources: Results and problems

The development of a system intended as a demonstrator for improving the tracking of distant point-like sources through the correction of the atmospheric optical distortions is here reported. The demonstrator consists of a motorized mirror, which can pursuit a moving light source, united to an adaptive optics setup to improve the performances and the precision of the tracing of the object trajectory. The adaptive optics setup consists of a closed loop between a quad cell sensor and a tip-tilt mirror for the atmospheric jitter compensation and of another closed loop between a Shack-Hartmann sensor and a membrane deformable mirror for the compensation of higher order aberrations. Atmospheric measurements of an incoherent source will be also presented. In the case of our interest, where the atmospheric disturbances cannot be addressed only to a turbulent layer near the pupil (near field approximation), the scintillation becomes an important part of the noise. Its effects w ill be analyzed here, with particular attention to the influence on the wavefront sensor.