Nouvelles recherches sur l'ensemble paléochrétien et médiéval d'Ereruyk en Arménie

Premiers résultats des campagnes d'investigations menées en 2009-2011 sur le site paléochrétien et médiéval d'Ereruyk, dans le nord-ouest de la république d'Arménie, par une équipe du LA3M (UMR 7298, Aix-Marseille Université / CNRS)

Exoplanet imaging with ELTs: exploring a second-stage AO with a Zernike wavefront sensor on the ESO/GHOST testbed

We propose to explore a cascade extreme Adaptive optics (ExAO) approach with a second stage based on a Zernike wavefront sensor (ZWFS) for exoplanet imaging and spectroscopy. Most exoplanet imagers currently use a single-stage ExAO to correct for the effects of atmospheric turbulence and produce high-Strehl images of observed stars in the near-infrared. While such systems enable the observation of warm gaseous companions around nearby stars, adding a second-stage AO enables to push the wavefront correction further and possibly observe colder or smaller planets. This approach is currently investigated in different exoplanet imagers (VLT/SPHERE, Mag-AOX, Subaru/SCExAO) by considering a Pyramid wavefront sensor (PWFS) in the second arm to measure the residual atmospheric turbulence left from the first stage. Since these aberrations are expected to be very small (a few tens of nm in the near-infrared domain), we propose to investigate an alternative approach based on the ZWFS. This sensor is a promising concept with a small capture range to estimate residual wavefront errors thanks to its large sensitivity, simple phase reconstruction and easiness of implementation. In this contribution, we perform preliminary tests on the GHOST testbed at ESO to validate this approach experimentally. Additional experiments with petalling effects are also showed, giving promising wavefront correction results. Finally, we briefly discuss a first comparison between PWFS-based and ZWFS-based second-stage AO to draw preliminary conclusions on the interests of both schemes for exoplanet imaging and spectroscopy with the upgrade of the current exoplanet imagers and the envisioned ExAO instruments for ELTs.Comment: 17 pages, 10 figures, pre-print of the proceeding of the AO4ELT7 conference held in June 2023 in Avignon, Franc

Enabling and Enhancing Science Exploration Across the Solar System: Aerocapture Technology for SmallSat to Flagship Missions

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The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI

The GRAVITY instrument has been revolutionary for near-infrared interferometry by pushing sensitivity and precision to previously unknown limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer (VLTI) in GRAVITY+, these limits will be pushed even further, with vastly improved sky coverage, as well as faint-science and high-contrast capabilities. This upgrade includes the implementation of wide-field off-axis fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser guide stars in an upgraded facility. GRAVITY+ will open up the sky to the measurement of black hole masses across cosmic time in hundreds of active galactic nuclei, use the faint stars in the Galactic centre to probe General Relativity, and enable the characterisation of dozens of young exoplanets to study their formation, bearing the promise of another scientific revolution to come at the VLTI.Comment: Published in the ESO Messenge

Development of a probe for in-situ radiative heat flux measurements at the surface of an ablator

International audienceWe present a radiative heat flux probe capable of directly accessing a radiative boundary layer around an ablative sample. Unlike previous approaches that have suffered from pollution of the optical system by ablative species, our probe utilizes a system for preventing contamination of the optical system. We are therefore able to make measurements over a long period of time during testing in a plasma torch facility. The probe operates on a battery-powered system and can therefore be installed in facilities without optical access. It is designed for use under a wide variety of conditions within ground test facilities. Prototype tests of the probe were performed in our 50 kW plasma torch facility to study an equilibrium air flow around an ablative CBCF turning wedge and flat surface samples. Further tests of the probe were performed in the much larger plasmatron facility at VKI to demonstrate probe functionality

Composite Structure for Deep Space CubeSats

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Reentry Platform for Radiation Studies

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