Jean Gabriel Cuby

EAGLE MOAO system conceptual design and related technologies

EAGLE is the multi-object spatially-resolved near-IR spectrograph instrument concept for the E-ELT, relying on a distributed Adaptive Optics, so-called Multi Object Adaptive Optics. This paper presents the results of a phase A study. Using 84×84 actuator deformable mirrors, the performed analysis demonstrates that 6 laser guide stars (on an outer ring of 7.2 diameter) and up to 5 natural guide stars of magnitude R < 17, picked-up in a 7.3 diameter patrol field of view, allow us to obtain an overall performance in terms of Ensquared Energy of 35% in a 75×75mas2 resolution element at H band whatever the target direction in the centred 5 science field for median seeing conditions. In terms of sky coverage, the probability to find the 5 natural guide stars is close to 90% at galactic latitudes |b| ~ 60 deg. Several MOAO demonstration activities are also on-going.

Come-on-plus project: an upgrade of the come-on adaptive optics prototype system

This paper is a presentation of the Come-On-Plus adaptive optics system, based on the Come-On prototype. Come-On-PIus will be set up in 1992 on the ESO 3.6 m telescope in La Silla (Chile). It is an upgrade of the Come-On instrument, with a 52 actuator deformable mirror, and 30 Hz correction bandwidth. But the main improvement concerns the wavefront sensing, designed in this instrument for astronomical applications, with a high detectivity wavefront sensor and a specific mirror control algorithm. This system is planned for routine astronomical observing as well as providing design parameters for the adaptive optics system of the ESO Very Large Telescope (VLT).

Electron-bombarded CCD: first results with a prototype tube

The aim of this paper is to show the relevance of the electron bombardment technique of photon counting for astronomical applications, using results obtained both in the laboratory and on the sky with a prototype tube. The potential astronomical applications discussed are in techniques requiring high time resolution, either in an analog or a photon counting mode (wavefront analysis, speckle interferometry, multitelescope interferometry, etc.) and observation of rapidly varying objects. Current prototypes will be used to achieve wavefront analysis in the near future. The first priority in further technical development must obviously be to develop a larger and faster CCD.

Modeling highly aspherical optical surfaces using a new polynomial formalism into Zemax

We developed a new mathematical formalism to model highly aspherical optical surfaces opening the possibility to explore innovative optical designs. This formalism is based on Bernstein polynomials allowing to describe from low to high order deformations of the optical surface. It has been implemented into Zemax making use of the User-Defined Surface (UDS-DLL) Zemax capability. In this case, the mathematical definition of the surface is imported into Zemax then allowing to apply classical optimization and analysis functionalities. This paper presents the UDS-DLL tool based on Bernstein polynomials together with an initial optical analysis performed to evaluate the gain obtained in using such a new formalism.

Wavefront sensing in imaging through the atmosphere: a detector strategy

Wavefront sensing is a very powerful technique whose capability in the field of diffraction- limited imaging through turbulence has been demonstrated. The ultimate performance of a Hartmann-Shack wavefront sensor is analyzed and used to define a detector choice strategy.

Active Optics techniques and complex instrumentation for future ELTs

In the frame of the future European Extremely Large Telescope, the Laboratoire d’Astrophysique de Marseille is developing manufacturing methods and complex instrumentation for astronomy, based on the active bending of mirrors.

Toward high-dynamic active mirrors for LGS refocusing systems

In the frame of the E-ELT-EAGLE instrument phase A studies, we designed a convex VCM able to compensate for the focus variation on the Laser Guide Star (LGS) wavefront sensor, due to the elevation of the telescope and the fixed sodium layer altitude. We present an original optical design including this active convex mirror, providing a large sag variation on a spherical surface with a 120mm clear aperture, with an optical quality better than lambda/5 RMS up to 820μm of sag and better than lambda/4 RMS up to 1000μm of sag. Finite element analysis (FEA) allowed an optimisation of the mirrors variable thickness distribution to compensate for geometrical and material non linearity. Preliminary study of the pre-stressing has also been performed by FEA, showing that a permanent deformation remains after removal of the loads. Results and comparison with the FEA are presented in the article of F.Madec et al (AS10-7736-119, this conference), with an emphasis on the system approach.