Pyramid sensors for AO and co-phasing Two key projects in Arcetri AO groups for 8m class telescopes and ELT wavefront sensing: -WFS for LBT AO system -Segment co-phasing for EELT

Pyramid WFS in Adaptive Optics A Strehl Ratio plot (peak value of the corrected PSF normalized to peak value for perfect correction) as a function of guide star magnitude in R band for Pyramid Sensor (PS) and Shack-Hartmann sensor (SH). PS is less sensitive to uncorrected atmospheric perturbations. Energy left In the PSF halo is 1/3 for PS. Enabling higher PSF contrast. PS achieve same performance With a star about 2 mag fainter. AO system sky coverage is doubled. SH PS Strehl Ratio in seeing limited case (8m tel.)

AO system for LBT -An astronomical AO system with two key components: 1) DM: a deformable secondary with 672 actuators. 2) Sensor: a pyramid WFS with up to 30x30 subapertures. -AO system coupled to 1-2.5 mm DL imager & spectrograph LUCIFER the main LBT instrument for diffraction limited observations Project main dates: -AO #1 comm. date: Dec08 -AO #2 comm. date: Sep09 FLAO on LBT telescope The secondary unit The pyramid WFS unit

A closer view to WFS unit Wavefront sensing W unit Acquisition & guiding AG unit The WFS board during integration The glass pyramid for LBT WFS

Closed loop lab test of the AO system The lab set-up for AO system test Closed loop lab test of the AO system 45-actuator prototype The 45 actuators prototype of deformable secondary WFS unit

Segment co-phasing for the ELT Arcetri AO group demonstrated that the Pyramid sensor can detect simultaneously segment differential piston as well as tip and tilt of the segments. -A single WFS for segmented mirror alignment -A single WFS for co-phasing and AO Closed loop alignment of the segmented DM of NAOMI AO system @ WHT [Opt.Lett.,Esposito,2005] Piston signals, (X,Y) Tip tilt rms Piston rms Tilt signals (X,Y)

The active Phasing Experiment (APE) Active Phasing Experiment (APE) is the WP4600 of the ELT Design Study. Experiment is aimed to realize , test and compare three co-phasing Sensor in lab at ESO and at the VLT. Initial rms > λ/2 Co-phasing loop: Start 110nm rms Stop 12nm rms Final rms 23nm

New projects: LGS GLAO system for LBT MCAO for EELT phase A study A project to provide LBT with a Laser Guide Star Ground Layer AO system is started as phase A study in May07. The program has an upgrade path aimed to extend GLAO system to LGS diffraction limited AO for imaging on small FoV. -GLAO system will be coupled with the multi-object spectroscopic unit of LUCIFER having a 4x2 arcmin FoV. MCAO for EELT phase A study ONERA Oss. Ast. Padova A 2 years phase A study to analize the design of a Multi-Conjugate AO system for the EELT leaded by Osservatorio di Bologna (OAB).