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 40×40 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.
MATISSE is the 2nd generation mid-infrared (3.0μm to 12.0μm) spectro-interferometric instrument of the Very Large Telescope Interferometer (VLTI). It was designed to deliver its advertised performance when supported by an external fringe tracker. This proceeding gives an historical account of how the fringe tracker of the GRAVITY instrument, another 2nd generation K-band spectro-astrometric instrument of VLTI, became this external fringe tracker. For a more technical and performance-oriented description of the GRAVITY for MATISSE project, Woillez, Petrov, et al. (2024) should be consulted.
We discuss a new generation fringe tracker (FT) that implements a Hierarchical Fringe Tracker (HFT) architecture with a very broad band near infrared spectral coverage from 1.1 to 2.2μm in the J, H and K bands. The goal is to approach the absolute maximum fringe tracking sensitivity in optical long baseline interferometry, first on the VLTI, and to show that an HFT has performances independent from the number of apertures, a key characteristic for larger interferometers from CHARA to the VLTI with more UTs or combining all UTs and ATs to future very large interferometers. This paper describes the development in progress of an end-to-end simulator of such a system based on our first laboratory tests of prototype HFT. This simulator already allowed us to define a new optimization for the integrated optics HFT chips, to discuss a set of operating parameters for our new generation fringe tracker and to confirm that it is applicable to an indefinite number of apertures and should approach or even exceed a limiting sensitivity on the VLTI of K~16, which is a gain of at least 3 magnitudes over the expected performance of the current GRAVITY FT in the context of the ongoing GRAVITY+ VLTI upgrade.
Hierarchical Fringe Trackers (HFT) maximize the sensitivity and accuracy of fringe tracking. Their performances are independent from the number of apertures. They cophase pairs of telescopes, then pairs of pairs and so on. We report the key results of mathematical analysis, design, manufacturing, optical tests and simulated performances of 4 telescopes HFT chips for the VLTI and 6 to 8 telescopes HFT chips for CHARA or a VLTI extension. An end-to-end simulation with realistic input piston and flux, based on the experimental characterization of the signals on the test bench, validates the servo loop and state machine architectures and supports the performance analysis, confirming the expected performance gain of about 3 magnitudes (with a limiting magnitude K>16 on the VLTI with UTs) and the fact that the performances do not decrease with the number of apertures. The performance gain is based on the combination of the HFT architecture with a very broad band HFT covering the 1.1 to 2.2μm domain with 3 to 5 HFT chips working in broad sub bands in J, H and K. Analysis of fringe jumps and losses at the sensitivity limit show that an HFT manages then more efficiently than the standard pairwise architecture. The impact of HFT characteristics on AGN science programs for optical interferometers is illustrated, showing that this architecture is the key for fascinating applications including direct distance measurements of AGNs accurate enough to contribute to the Hubble tension problem.
The delivery of curated data from astronomical instruments has become a reality in many observatories. The European Southern Observatory (ESO) delivers science-ready data products for various instruments, ranging from imagers to integral field spectrographs. In the case of infrared long-baseline interferometry, scientists generally make their curated data available through the Optical Interferometry Database (OiDB) once it is published. We report on a project to create a curated data stream for the GRAVITY instrument at the Very Large Telescope Interferometer. We aim to transform the publicly available raw data in the ESO science archive into science-ready curated data.
The Very Large Telescope Interferometer (VLTI) is a wonderful infrastructure for long-baseline interferometry. MATISSE, the Multi AperTure mid-Infrared SpectroScopic Experiment, installed at the VLTI focus, accesses high resolution imaging over a wide spectral domain of the mid-infrared. The instrument is a spectro-interferometric imager operating in the L, M, and N transmission windows and combining four optical beams from the VLTI’s unit or auxiliary telescopes. We propose at the SPIE conference to advertise the use of the MATISSE instrument. We will illustrate the instrument capabilities through astrophysical results recently achieved (the focus on the astrophysical results is not reported in the article). We also show what are the expected future infrastructure optimizations and instrument adaptations (off-axis tracking, frame of GRAVITY+) that will permit to push the sensitivities and accuracies for the astrophysical programs in the context of the JWST.
The Very Large Telescope Interferometer (VLTI) is currently the best infrastructure for long-baseline interferometry in particular in terms of sensitivity and accessibility to the general user. MATISSE, installed at the VLTI focus since end of 2017, belongs to the second generation instruments. MATISSE, the Multi AperTure mid-Infrared SpectroScopic Experiment, for the first time accesses high resolution imaging over a wide spectral domain of the mid-infrared. The instrument is a spectro-interferometric imager in the atmospheric transmission windows called L, M, and N, from 2.8 to 13.0 microns, and combines four optical beams from the VLTI’s unit or auxiliary telescopes. The instrument utilises a multi-axial beam combination that delivers spectrally dispersed fringes. The signal provides the following quantities at several spectral resolutions: photometric flux, coherent flux, visibility, closure phase, wavelength differential visibility and phase, and aperture-synthesis imaging. MATISSE can operate as a stand alone instrument or with the GRA4MAT set-up employing the GRAVITY fringe tracking capabilities. The updated MATISSE performance are presented at the conference together with a selection of two front-line science topics explored since the start of the science operations in 2019. Finally we present the perspective and benefit of two technical improvements foreseen in the coming years: the MATISSE-Wide off-axis fringe tracking capability and new adaptive optics for the UTs in the context of the GRAVITY+ project.
VERMILION is a VLTI visitor instrument project intended to extend the sensitivity and the spectral coverage of Optical Long Baseline Interferometry (OLBIn). It is based on a new concept of Fringe Tracker (VERMILIONFT) combined with a J band spectro-interferometer (VERMILION-J). The Fringe Tracker is the Adaptive Optics module specific to OLBIn that measures and corrects in real time the Optical Path Difference (OPD) perturbations introduced by the atmosphere and the interferometer, by providing a sensitivity gain of 2 to 3 magnitudes over all other state of the art fringe trackers. The J band spectro-interferometer will provide all interferometric measurements as a function of wavelength. In addition to a possible synergy with MATISSE, VERMILION-J, by observing at high spectral resolution many strong lines in J (Paβ-γ, HeII, TiO and other metallic monoxides), will cover several scientific topics, e.g. Exoplanets, YSOs, Binaries, Active Hot, Evolved stars, Asteroseismology, and also AGNs.
Hierarchical Fringe Tracking (HFT) is a fringe tracking concept optimizing the sensitivity in optical long baseline by reducing to an absolute minimum the number of measurements used to correct the OPD fluctuations. By nature, the performances of an HFT do not decreases with the number of apertures of the interferometer and are set only by the flux delivered by the individual telescopes. This a critical feature for future interferometers with large number of apertures both for homodyne and heterodyne operation. Here we report the design and first optical bench tests of integrated optics HFT chips for a 4 telescopes interferometer such as the VLTI. These tests validate the HFT concept and confirm previous estimates that we could track accurately fringes on the VLTI up to nearly K~15.9 with the UTs and K~12.2 with the ATs with a J+H+K fringe tracker with one HFT chip per band. This is typically 2.5 magnitudes fainter than the best potential performance of the current ABCD fringe tracker in the K band. An active longitudinal and transverse chromatic dispersion correction allows the optimization of broad band fiber injections and instrumental contrast. We also present a preliminary evaluation of the potential of such a gain of sensitivity for the observations of AGNs with the VLTI.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.