Abstract. The need for both high quality images and lightweight structures is one of the main drivers in space telescope design. An efficient wavefront control system will become mandatory in future large observatories, retaining performance while relaxing specifications in the global system's stability. We present the mirror actively deformed and regulated for applications in space project, which aims to demonstrate the applicability of active optics for future space instrumentation. It has led to the development of a 24-actuator, 90-mm-diameter active mirror, able to compensate for large lightweight primary mirror deformations in the telescope's exit pupil. The correcting system has been designed for expected wavefront errors from 3-m-class lightweight primary mirrors, while also taking into account constraints for space use. Finite element analysis allowed an optimization of the system in order to achieve a precision of correction better than 10 nm rms. A dedicated testbed has been designed to fully characterize the integrated system performance in representative operating conditions. It is composed of: a telescope simulator, an active correction loop, a point spread function imager, and a Fizeau interferometer. All conducted tests demonstrated the correcting mirror performance and has improved this technology maturity to a TRL4. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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We analyze the multilayer structure of sunflower leaves from Terahertz data measured in the time-domain at a ps scale. Thin film reverse engineering techniques are applied to the Fourier amplitude of the reflected and transmitted signals in the frequency range f < 1.5 Terahertz (THz). Validation is first performed with success on etalon samples. The optimal structure of the leaf is found to be a 8-layer stack, in good agreement with microscopy investigations. Results may open the door to a complementary classification of leaves.

ADONIS (ADaptive Optics Near Infrared System) is an upgrade ofthe C0ME-oN+ adaptive optics prototype. It will allow the astronomical community to use adaptive optics as a common user instrument. This paper describes the main features of the new system, including a mechanical and optical interface for specific visitor equipment and imaging capabilities. We present here the 128 x 128 infrared imaging camera, covering the 1-5 pm spectral range. Two interchangeable scales (35 and 100 milli-arcsec) can be selected to match the diffraction pattern respectively in J (1.25 pm) and L (3.6 pm) bands. A second imaging camera built by the Max-Planck-Institut fur Extraterrestrische Physik (Garching) covering the 1-2.5 pm region, is currently used by the European community for regular astronomical observations. The new real-time computer architecture and the associated control software are presented. It will allow the implementationofan open Artificial Intelligence software that will control the large number ofparameters such as bench configuration, infrared camera set-up, real-time computer initialization, telescope control system, seeing and meteo site sensor data acquisition and astronomical observing program organisation. In addition to its scientific use at La Silla, ADONIS will bring a substantial experience in optimizing the operation of an adaptive optics system, in particular in the VLT prospect. O-8194-/496-4/94/$6.OO SP1E Vol. 2201 Adaptive Optics in Astronomy (1994) / 955 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx SPIE Vol. 2201 Adaptive Optics in Astronomy (1994) / 957 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

Highly performing adaptive optical (AO) systems are mandatory for next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes, for studying new fields like circumstellar disks and extra-solar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500µm. MOEMS-based devices are promising for future deformable mirrors. We are currently developing a micro-deformable mirror (MDM) based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. In order to reach large stroke for low driving voltage, the originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials. We have developed the first polymer piston-motion actuator: a 10µm thick mobile plate with four springs attached to the substrate, and with an air gap of 10µm exhibits a piston motion of 2µm for 30V, and measured resonance frequency of 6.5kHz is well suited for AO systems. The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. We have successfully developed a dedicated 14-bit electronics in order to ''linearize'' the actuation. Actual location of the actuator versus expected location of the actuator is obtained with a standard deviation of 21 nm. Comparison with FEM models shows very good agreement, and design of a complete polymer-based MDM has been done.