Adaptive Optics Facility. When cutting-edge technology meets operational robustness and performance

The Adaptive Optics Facility (AOF) is an ESO project started in 2005, which transformed Yepun, one of the four 8m telescopes in Paranal, into an adaptive telescope. This has been done by replacing the conventional secondary mirror of Yepun by a 1172 actuator Deformable Secondary Mirror (DSM) and attaching four Laser Guide Star (LGS) Units to its centerpiece, each of them featuring a high stability narrow-band 20 W laser. Additionally, two Adaptive Optics (AO) modules (GALACSI serving MUSE a 3D spectrograph, and GRAAL, serving Hawk I a wide field infrared imager) have been assembled onto the telescope Nasmyth adapters, each of them incorporating four LGS WaveFront Sensors (WFS) and one tip-tilt sensor used to control the DSM at 1 kHz frame rate. These WFSs are based on 0 Read-out Noise (RoN) detectors. The complete AOF has been operated on-sky for more than 2 years and is routinely delivering science. This paper presents the most important and amazing features of the AOF, focusing on cutting-edge technology in use, operational concept and overall performance. In the first part of the paper, the AOF design is recalled, with a focus on the DSM, the lasers, the WFS cameras and the Real Time Computer technology. Then, the acquisition sequence and overall on-sky operation efficiency will be detailed; finally, on-sky performance of AOF will be presented.