CEDRAT TECHNOLOGIES Innovation in Mechatronics Piezo actuators for Astronomical instrumentation In astronomical instrumentation, the trend is currently to build up large telescopes. Such structures enable to gather more light and hence, to see our universe brighter. Numerous projects like VLT, ELT, TMT … are well known cases showing the tendency. Fig. 1: CEDRAT TECHNOLOGIES piezoelectric actuators The full-size telescopes are sensitive to their environment. The challenge is to eliminate the external disturbances which lower the image quality. The disturbances can be environmental factors like gravity, wind, telescope axis deformation… or less intuitive factors like wave front distortion by the atmosphere. Telescopes are hence equipped with real-time monitoring systems controlling and adapting the position and shape of the mirrors by piston, tilt and steering operations. CEDRAT TECHNOLOGIES ACTUATORS Fig. 2: Extremely Large Telescope ( ELT ) ESO/L. Calçada CEDRAT TECHNOLOGIES (CTEC) designs actuators and mechanisms (Fig.1) to answer to the compact, dynamic and precise motion requirement from the astronomical instrumentation designer and manufacturer. Here below we show some applications in the field of astronomy. Fig. 3: Actuator APA500XXL for M5 field stabilization EXTREMELY LARGE TELESCOPE (ELT) - ESO CTEC has been involved in the development & delivery of several piezo actuators and mechanisms for criticlal subsytem parts of the ELT (fig.2) stucture and instrumentation like M5 filed stabilization unit and MICADO instrumentation detailed in the paragraphs below. Copyright © CEDRAT TECHNOLOGIES | 10/2020 ELT - M5 FIELD STABILIZATION UNIT - ESO The aim is to generate a dynamic tip-tilt motion with stabilized piston motion on the M5 tip-tilt elliptical mirror of 2.7 m x 2.2 m and 430 kg mass in the Extremely Large Telescope (ELT). The actuation is made by three heavy duty APA500XXL (Fig.3) piezo actuators with 500 µm stroke and 30 kN blocked force under 1 kV voltage. This high force and stiffness make this APA500XXL a certified robust actuator to earthquakes. The first prototypes delivered to SENER with CSEM collaboration fulfilled ESO specifications (Fig.4). To reach the specified 30 years minimum of operations, CTEC decided to encapsulate the piezo stack into a bellows assembly (Fig.5&6) to protect the piezo ceramic against humidity and then increase significantly the Mean Time To Failure (MTTF) of the APA500XXL. Fig. 4: APA500XXL integrated in the Tip Tilt platform of the M5 field Stabilization unit CEDRAT TECHNOLOGIES • 59 Chemin du Vieux Chêne • Inovallée • 38246 MEYLAN Cedex France • Tel. : +33 (0

CEDRAT TECHNOLOGIES Innovation in Mechatronics Piezo actuators for Astronomical instrumentation Thanks to its high resolution, the APA500XXL, coupled with an optimized close-loop control, allows to compensate perturbations caused by the telescope mechanisms and wind vibrations, with an accuracy of few micro-radians and 10 Hz bandwidth and alignment system in three degrees of freedom (Z, Rx, Ry) for the fifth mirror positioning. Although the M5 mirror will be the smallest mirror on the ELT, it will be the largest tip-tilt stabilized mirror in the world that will compensate perturbations caused...

CEDRAT TECHNOLOGIES Innovation in Mechatronics > Piezo actuators for Astronomical instrumentation BEAM STEERING MIRROR (CELTIC PROJECT) - LAM The astronomical laboratory of Marseille (LAM) has developed a beam steering mirror (BSM) using actuators APA230L (Fig.9) and power electronics from CTEC. The BSM has been designed according to the specifications required on an ELT instrument and can perform translation, tip-tilt and deformation. The active surface deformation is meant to compensate for astigmatism introduced by spherical pickoff mirrors. A prototype has shown that this design allows to...