arXiv subjects

Thibaut Moulin

Publications and source records attributed to Thibaut Moulin.

6 recordsLinked to original sources

arXiv2026

MORFEO: Advancing Towards Final Design

The Multiconjugate adaptive Optics Relay For ELT Observations (MORFEO) is a first-generation adaptive optics module for the Extremely Large Telescope (ELT), designed to deliver a diffraction-limited, highly uniform 53x53 arcsec field of view to the MICADO near-infrared camera. As the project advances toward its Final Design Review (FDR), significant consolidations have been achieved across all subsystems. This paper presents an updated overview of the MORFEO system, highlighting its dual operational modes (MCAO and SCAO) and recent developments in its opto-mechanical architecture. We dedicate specific focus to the core adaptive hardware, detailing the fifth-generation post-focal deformable mirrors, the highly complex Laser Guide Star (LGS) objective zoom system required to track sodium layer variations, and the Natural Guide Star (NGS) low-order and reference sensing strategies. Furthermore, we detail the advanced pseudo-open-loop control strategy managed by a split Hard and Soft Real-Time Computer architecture. Finally, we report the latest end-to-end performance estimations obtained via the SPECULA simulation framework, demonstrating compliance with the stringent Strehl Ratio and sky coverage requirements under median atmospheric conditions.

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arXiv2022

HARMONI at ELT: A Zernike wavefront sensor for the high-contrast module -- Testbed results with realistic observation conditions

ELT-HARMONI is the first light visible and near-IR integral field spectrograph (IFS) for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews. The High Contrast Module (HCM) will allow HARMONI to perform direct imaging and spectral analysis of exoplanets up to one million times fainter than their host star. Quasi-static aberrations are a limiting factor and must be calibrated as close as possible to the focal plane masks to reach the specified contrast. A Zernike sensor for Extremely Low-level Differential Aberrations (ZELDA) will be used in real-time and closed-loop operation at 0.1Hz frequency for this purpose. Unlike a Shack-Hartmann, the ZELDA wavefront sensor is sensitive to Island and low-wind effects. The ZELDA sensor has already been tested on VLT-SPHERE and will be used in other instruments. Our objective is to adapt this sensor to the specific case of HARMONI. A ZELDA prototype is being both simulated and experimentally tested at IPAG. Its nanometric precision has first been checked in 2020 in the case of slowly evolving, small wavefront errors, and without dispersion nor turbulence residuals. On this experimental basis, we address the performance of the sensor under realistic operational conditions including residuals, mis-centring, dispersion, sensitivity, etc. Atmospheric refraction residuals were introduced by the use of a prism, and turbulence was introduced by a spatial light modulator which is also used to minimise wavefront residuals in a closed loop in the observing conditions expected with HARMONI.

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arXiv2022

Coronagraphy for DiRect Imaging of Exoplanets (CIDRE) testbed 1: concept, optical set up, and experimental results of adaptive amplitude apodization

Oncoming exoplanet spectro-imagers like the Planetary Camera and Spectrograph (PCS) for the Extremely Large Telescope (ELT) will aim for a new class of exoplanets, including Earth-like planets evolving around M dwarfs i.e., closer than 0.1'' with contrasts around 10^-8. This can be achieved with coronagraphs to modulate the wavefront. Classical coronagraphs are not optimal: 1) they impose a planetary photon loss, which is particularly problematic when the instrument includes a high spectral-resolution spectrograph, 2) some aberrations such as the missing segments of the ELT are dynamic and not compatible with a static coronagraph design, 3) the coupling of the exoplanet image with a fiber for spectroscopy only requires the electric field to be controlled on a small region of the detector. Such instruments would benefit from an adaptive tool to modulate the wavefront in both amplitude and phase. We propose to combine in the pupil plane a deformable mirror (DM) to control the phase and a digital micro-mirror device (DMD) i.e., an array made of 1920*1080 micro-mirrors able to switch between two positions, to control its amplitude. If the DM is already well-known in the field in particular for adaptive optics applications, the DMD has so far not been fully considered. At IPAG, we are currently assembling a testbed called CIDRE (Coronagraphy for DiRect Imaging of Exoplanets) to develop, test, calibrate, and validate the combination of these two components with a Lyot coronagraph. Since March 2022, CIDRE is assembled albeit without the Lyot coronagraph yet. The first few months have been dedicated to the calibration of the DMD. Since May 2022, it is operational and used to test dynamic amplitude apodization coronagraphs (so-called Shaped Pupils). This proceeding presents the set up of the CIDRE testbench and the first experimental results on adaptive Shaped Pupils obtained with the DMD.

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arXiv2022

HARMONI at ELT: designing a laser guide star wavefront sensors for the ELT

HARMONI is the first light visible and near-IR integral field spectrograph for the ELT covering a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes-SCAO and LTAO-or with no AO. The project is preparing for Final Design Reviews. The laser Tomographic AO (LTAO) system provides AO correction with very high sky-coverage thanks to two systems: the Laser Guide Star Sensors (LGSS) and the Natural Guide Star Sensors (NGSS). LGSS is dedicated to the analysis of the wavefront coming from 6 laser guide stars created by the ELT. It is made of 6 independent wavefront sensor (WFS) modules mounted on a rotator of 600mm diameter to stabilise the pupil onto the microlens array in front of the detector. The optical design accepts elongated spots of up to 16 arcsec with no truncation using a CMOS detector from SONY. We will present the final optical and mechanical design of the LGSS based on freeform lenses to minimize the numbers of optical components and to accommodate for the diversity of sodium layer configurations. We will focus on rotator design, illustrating how we will move 1 tons with 90" accuracy in restrictive environment. Finally, we will present the strategy to verify the system in HARMONI context. The main challenge for the verification being how to test an AO system without access to the deformable mirror, part of the ELT.

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arXiv2018

Multiple Star Systems in the Orion Nebula

This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium Cluster with the recently comissioned GRAVITY instrument. We observe a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for $θ^1$ Ori B, $θ^2$ Ori B, and $θ^2$ Ori C. We determine a separation for the previously suspected companion of NU Ori. We confirm four companions for $θ^1$ Ori A, $θ^1$ Ori C, $θ^1$ Ori D, and $θ^2$ Ori A, all with substantially improved astrometry and photometric mass estimates. We refine the orbit of the eccentric high-mass binary $θ^1$ Ori C and we are able to derive a new orbit for $θ^1$ Ori D. We find a system mass of 21.7 $M_{\odot}$ and a period of $53$ days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about 2, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints towards a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We exclude collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.

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arXiv2018

Characterisation of ALPAO deformable mirrors for the NAOMI VLTI Auxiliary Telescopes Adaptive Optics

The Very Large Telescope Interferometer Auxiliary Telescopes will soon be equipped with an adaptive optics system called NAOMI. The corrective optics deformable mirror is the commercial DM241 from ALPAO. Being part of an interferometer operating from visible to mid-infrared, the DMs of NAOMI face several challenges (high level of reliability, open-loop chopping, piston-free control, WFS/DM pupil rotation, high desired bandwidth and stroke). We here describe our extensive characterization of the DMs through measurements and simulations. We summarize the operational scenario we have defined to handle the specific mirror properties. We conclude that the ALPAO DMs have overall excellent properties that fulfill most of the stringent requirements and that deviations from specifications are easily handled. To our knowledge, NAOMI will be the first astronomical system with a command in true Zernike modes (allowing software rotation), and the first astronomical system in which a chopping is performed with the deformable mirror (5'' sky, at 5~Hz).

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