Four-telescope fringe trancking for GRAVITY and precision astrometry
type: Distribution
access URL: https://theses.hal.science/tel-00772392
format: HTML
issued: 2026-05-15T10:42:39.705964
modified: 2026-05-15T10:42:39.602296

test_moissonnage_selune
type: Agent

Four-telescope fringe trancking for GRAVITY and precision astrometry
type: Dataset
contact point: Organization
  fn: CCSD
keyword: gravity
keyword: physastrimphysics-physicsastrophysics-astro-phinstrumentation-and-methods-for-astrophysic
keyword: high-angular-resolution
keyword: suivi-de-franges
keyword: sduastrsrsciences-of-the-universe-physicsastrophysics-astro-phsolar-and-stellar-astrophysi
keyword: physastrsrphysics-physicsastrophysics-astro-phsolar-and-stellar-astrophysics-astro-phsr
keyword: sduastrimsciences-of-the-universe-physicsastrophysics-astro-phinstrumentation-and-methods
keyword: haute-resolution-angulaire
keyword: turbulence-atmospherique
keyword: theses
keyword: atmopsheric-turbulence
keyword: fringe-tracking
keyword: interferometrie-optique
keyword: infoeu-reposemanticsdoctoralthesis
keyword: optical-interferometry
landing page: https://theses.hal.science/tel-00772392
description: My PhD was initiated in the framework of the development of GRAVITY, second generation instrument for the VLTI, whose first light is expected for 2014. GRAVITY will combine up to four telescopes in the K infrared spectral band (~2.2 µm). By stabilizing the phase of a reference star of magnitude as faint as K=10, this instrument will enable astrometric measurements with a precision of 10 µas on objects of magnitude up to K=15, and phase referenced imaging on objects as faint as K=16 with about 4mas angular resolution. The goal of my PhD consists in developing the fringe tracker algorithms of GRAVITY, a critical sub-system to reach these sensitivity limits unequaled in infrared long-baseline interferometry. To enable integrations longer than 100 s on the science beam, the fringe tracker will have to stabilize the optical path differences, with residues as low as 350 nm rms on the reference star, despite disturbance due to atmospheric piston, instrumental vibrations, and variations of flux in the recombined beams. In this aim, I performed numerical simulations of the whole control loop, by realistically modeling different disturbance sources inducing path length fluctuations in the beams, and flux variations in the beams. I demonstrated that fringes will be stabilized down to 310 nm rms on a K=10 magnitude star with the expected observing conditions at VLTI in 2014, with a predictive controller based on Kalman filtering that uses a disturbance model to compute the actuator commands. However, I showed that this performance strongly decreases for less optimistic conditions. In addition, I analyzed the efficiency in correcting both atmospheric piston and vibrations of the Kalman controller, compared to the algorithms currently used at VLTI. From on-sky phase measurements with the PRIMA instrument at VLTI, I showed that the disturbances are better corrected with the Kalman controller than with the PRIMA-FSU. Moreover, I performed numerical simulations demonstrating that th…
issued: 2026-05-15T10:42:39.632256
language: fr
modified: 2026-05-15T10:42:39.632262