1 1 st Light AO 4 LBT Pyramid WFS Adaptive Secondary MMT Unit

2 The two main system characteristic Adaptive Secondary MMT Unit LBT AdSec unit: LBT actuators 1ms average settling time Perform WF reconstruction Pyramid WFS WFS board (300x400) moveable for source acq. Adj. samp. 30x30,15x15,10x10…(on-chip binning) RON 3.5 Lim R mag: 16.7 (0.2 on axis SR, 0.6” r0) Use of LLLCCD CCD60 128x128 WFS camera EEV39/L3CCD Acquisition camera WFS path ACQ. Camera path

3 ELTs application of LBT AO components Adaptive secondaries technologies to be used for adaptive segments for ELTs. Use of Pyramid WFS as co-phasing sensor for ELTs segmented mirrors Use of Pyramid sensor as High Order WFS > 100 subapertures Use of LLL CCD in future ELTs AO system. Needs for many pixels 256x256 and 1Kfps speed with low RON <1e- JRA1: High Order WFS comparison : Development of Adaptive secondaries having 1500 acts. Fundings form European Community FP6 : Co-phasing sensor to test at VLT (APE experiment) : Development of adaptive segments

4 Adaptive Primary: OWL case Using AdSec technique for OWL [pitch mm] OWL OWL optical train M1100m Spherical 1 M233.5m Flat 3 M3 8.2m Aspherical 12 M48.1mAspherical 12 M5 4.2 m Aspheric 24 M62.4mElliptical 42 M54.2m km M62.4m 42 0km courtesy A. Riccardi M6 2.5m (0km) act. Pitch 27mm 6060 acts M5 4.2m (7.8km) act. Pitch 80mm 2190 acts Adaptive segments for M1 or M2 ? Overall fitting error 290nm (Kband) P. Dierickx, SPIE 2002, Hawaii K band Adaptive surfaces

5 Co-Phasing Using Pyramid Sensor PWFS (2) assembly FISBA interf. Unit (1) Unit for (3) Differential piston FISBA Diff. Pist unit PWFS Aim of the set up is to measure at the same time a certain differential piston introduced using (3) with the two instrument FISBA (1) and PWFS (2). Reflecting surfaces of the cubes actuator for cube displacements The lab unit devoted to introduce A differential piston

6 WFS signal versus differential piston Initial signal value End signal value time Dinamical behaviour of the DP signal on a single pixel when the DP is changing in time of more than 4  Signal computation uses the same formula used for wavefront Derivative estimation Pupil images on CCD 2D signal from pupils

7 Differantial piston measurement accuracy RMS of pyramid measurement with respect to fitting values is 15.8 nm (9 deg in phase angle) RMS of pyramid measurement with respect to fitting values is 15.8 nm (9 deg in phase angle) Comparison of interferometer and pyramid measurements of the same differential piston,using: 1)LBT pyramid wavefront sensor (Y axis) and 2)FISBA interferometr (X axis).

8 Pyramid Sensor sensitivity Signal amplitude measured in lab as a function of the tilt modulation showing an inversely proportional law. The wavefront error due to pure photon noise can be stimated using the sensitivity measurements. In particular considering a segment of 2.1 m 2, a 15 magnitude star and 30 s exposion, we found a residual differential piston error on the wavefront of 7.3 nm The wavefront error due to pure photon noise can be stimated using the sensitivity measurements. In particular considering a segment of 2.1 m 2, a 15 magnitude star and 30 s exposion, we found a residual differential piston error on the wavefront of 7.3 nm