arXiv subjects

Roderick Dembet

Publications and source records attributed to Roderick Dembet.

6 recordsLinked to original sources

arXiv2026

The MICADO first-light imager for the ELT: first steps of the SCAO system MAIT

MICADO is the ELT first light instrument, an imager working at the diffraction limit of the telescope thanks to two adaptive optics (AO) modes: a single conjugate one (SCAO), available at the instrument first light and developed by the MICADO consortium, and a multi conjugate one (MCAO), developed by the MORFEO consortium. Although the project final design review process is about to be completed, the review board and ESO acknowledged that "the review of the final design can be considered complete for the majority of the MICADO sub-systems" and agreed that MICADO can start manufacturing. For the MICADO SCAO module, we have started the manufacturing of several parts: the majority of the SCAO optics and of the SCAO mechanics, the real-time computer software and the instrument control software. This manufacturing is ordered in several steps to allow the progressive integration of a first full AO close loop with the final SCAO parts. In this contribution, we will focus on the first two steps: on our AO S\'esame bench and the so-called "beta flat configuration". We will present the status of this manufacturing and the first results obtained.

astro-ph.IM↗

arXiv2026

The MICADO first light imager for the ELT: the SCAO module AIT in France, from the beta flat configuration towards the flat and final configurations

MICADO is the designated ELT first light instrument, a near-infrared imager working at the diffraction limit of the telescope thanks to a SCAO and an MCAO mode. Since summer 2024, MICADO is in its AIT phase and all MICADO partners are currently integrating their subsystems. The MICADO SCAO module will follow three successive AIT phases in France: the beta flat configuration, the flat configuration and the final configuration. In this contribution I will first present the progress made in the AIT of the beta flat configuration and its closed loop results. I will then present the performed and on-going tasks for the flat and final configurations (manufacturing, delivery and integration of several SCAO subsystems and pieces of software) and the results obtained so far in the flat configuration. I will then conclude with the expected following steps of the SCAO module AIT in Garching.

astro-ph.IM↗

arXiv2025

GRAVITY+ adaptive optics (GPAO) tests in Europe

We present in this proceeding the results of the test phase of the GRAVITY+ adaptive optics. This extreme AO will enable both high-dynamic range observations of faint companions (including exoplanets) thanks to a 40x40 sub-apertures wavefront control, and sensitive observations (including AGNs) thanks to the addition of a laser guide star to each UT of the VLT. This leap forward is made thanks to a mostly automated setup of the AO, including calibration of the NCPAs, that we tested in Europe on the UT+atmosphere simulator we built in Nice. We managed to reproduce in laboratory the expected performances of all the modes of the AO, including under non-optimal atmospheric or telescope alignment conditions, giving us the green light to proceed with the Assembly, Integration and Verification phase in Paranal.

astro-ph.IM↗

arXiv2023

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.

astro-ph.IM↗

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 $\theta ^1$ Ori B, $\theta ^2$ Ori B, and $\theta ^2$ Ori C. We determine a separation for the previously suspected companion of NU Ori. We confirm four companions for $\theta ^1$ Ori A, $\theta ^1$ Ori C, $\theta ^1$ Ori D, and $\theta ^2$ Ori A, all with substantially improved astrometry and photometric mass estimates. We refine the orbit of the eccentric high-mass binary $\theta ^1$ Ori C and we are able to derive a new orbit for $\theta ^1$ 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.

astro-ph.SR↗

arXiv2015

The GRAVITY instrument software / High-level software

GRAVITY is the four-beam, near- infrared, AO-assisted, fringe tracking, astrometric and imaging instrument for the Very Large Telescope Interferometer (VLTI). It is requiring the development of one of the most complex instrument software systems ever built for an ESO instrument. Apart from its many interfaces and interdependencies, one of the most challenging aspects is the overall performance and stability of this complex system. The three infrared detectors and the fast reflective memory network (RMN) recorder contribute a total data rate of up to 20 MiB/s accumulating to a maximum of 250 GiB of data per night. The detectors, the two instrument Local Control Units (LCUs) as well as the five LCUs running applications under TAC (Tools for Advanced Control) architecture, are interconnected with fast Ethernet, RMN fibers and dedicated fiber connections as well as signals for the time synchronization. Here we give a simplified overview of all subsystems of GRAVITY and their interfaces and discuss two examples of high-level applications during observations: the acquisition procedure and the gathering and merging of data to the final FITS file.

astro-ph.IM↗