The M4 adaptive unit for the E-ELT

Cilas proposes a M4 adaptive mirror (M4AM) that corrects the atmospheric turbulence at high frequencies and residual tip-tilt and defocus due to telescope vibrations by using piezostack actuators. The design presents a matrix of nearly 7000 actuators (hexagonal geometry, spacing equal to 29 mm) leading to a fitting error simulated by Onera reaching the fitting error goal. The mirror is held by a positioning system which ensures all movements of the mirror at low frequency and selects the focus (Nasmyth A or B) using a hexapod concept. This subsystem is fixed rigidly to the mounting system and permits mirror displacements. The M4 control system (M4CS) ensures the connection between the telescope control/monitoring system and the M4 unit - positioning system (M4PS) and piezostack actuators in particular. This subsystem is composed of electronic boards, mechanical support fixed to the mounting structure and the thermal hardware. With piezostack actuators, most of the thermal load is minimized and dissipated in the electronic boards and not in the adaptive mirror. The mounting structure (M4MS) is the mechanical interface with the telescope (and the ARU in particular) and ensures the integrity and stability of M4 unit subsystems. M4 positioning system and mounting structure are subcontracted to Amos company. We will also report on the manufacturing of the demonstration prototype that will be tested in the next phase. Keywords: Adaptive optic, Adaptive unit, E-ELT, hexapod, mirror, PZT actuato

Last progress concerning the design of the piezo stack M4 adaptive unit of the E-ELT

International audienceCILAS proposes a M4 adaptive mirror (M4AM) that corrects the atmospheric turbulence at high frequencies and residual tip-tilt and defocus due to telescope vibrations by using piezostack actuators. The design presents a matrix of 7217 actuators (triangular geometry, spacing equal to 29 mm) leading to a fitting error reaching the goal. The mirror is held by a positioning system which ensures all movements of the mirror at low frequency and selects the focus (Nasmyth A or B) using a hexapod concept. This subsystem is fixed rigidly to the mounting system and permits mirror displacements. The M4 control system (M4CS) ensures the connection between the telescope control/monitoring system and the M4 unit - positioning system (M4PS) and piezostack actuators of the M4AM in particular. This subsystem is composed of electronic boards, mechanical support fixed to the mounting structure and the thermal hardware. With piezostack actuators, most of the thermal load is minimized and dissipated in the electronic boards and not in the adaptive mirror. The mounting structure (M4MS) is the mechanical interface with the telescope (and the ARU in particular) and ensures the integrity and stability of M4 unit subsystems. M4 positioning system and mounting structure are subcontracted to AMOS company

Demonstration prototype and breadboards of the piezo stack M4 adaptive unit of the E-ELT

International audienceIn order to mitigate the risks of development of the M4 adaptive mirror for the E-ELT, CILAS has proposed to build a demonstration prototype and breadboards dedicated to this project. The objectives of the demonstration prototype concern the manufacturing issues such as mass assembly, integration, control and polishing but also the check the global dynamical and thermal behaviour of the mirror. The local behaviour of the mirror (polishing quality, influence function, print through...) is studied through a breadboard that can be considered as a piece of the final mirror. We propose in this paper to present our breadboard strategy, to define and present our mock-up and to comment the main results and lessons learned