MATISSE is the 2nd generation mid-infrared instrument designed to combine four VLTI telescopes in the L, M and N spectral bands. It’s commissioning in Paranal is in progress since March 2018 and should continue until the middle of 2019. Here we report, in June 2018, the commissioning plan, tools and the preliminary results of the first two commissioning runs in MATISSE that show that the instrument is already fully operational with a sensitivity well beyond its specification. The quality of the measurements, as they obtained by the current observing procedures and delivered by the current pipeline are already good enough for a broad range of science observations. However, our results remain quite preliminary and they will be quite substantially improved by the work in progress in instrument calibration, observing procedures optimization and data processing updates.
MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the spectro-interferometer for the VLTI of the European Southern Observatory (ESO), operating in the L-, M- and N- spectral bands, and combining up to four beams from the unit or the auxiliary telescopes (UTs or ATs). MATISSE will offer new breakthroughs in the study of circumstellar environments by allowing the mapping of the material distribution, the gas and essentially the dust. The instrument consists in a warm optical system (WOP) accepting four beams from the VLTI and relaying them after a spectral splitting to cold optical benches (COB) located in two separate cryostats, one in L-M- band, and one in N-band. The test plan of the complete instrument has been conducted at the Observatoire de la Côte d’Azur in order to confirm the compliance of the performance with the high-level requirements. MATISSE has successfully passed the Preliminary Acceptance in Europe the 12th September 2017. Following this result, ESO gave approval for the instrument to be shipped to Paranal. The Alignment, Integration and Verification phase was conducted until end of February 2018, at the end of which first observations on sky have been performed to test the operations with the VLTI and to obtain first stellar light. The two first runs of the commissioning followed, respectively in March and in May 2018. It has the goal to optimize the MATISSE-VLTI communication, the acquisition procedures and the interface parameters. The observations were performed on bright L-M- and N- stars, with four ATs located on short baselines and UTs. The limit magnitudes will be deduced.
This paper reports on the performance of the instrument measured in laboratory (results of test plan in Nice and AIV in Paranal) in terms of spectral coverage, dispersion laws and spectral resolutions, and transfer function analysis: instrumental contrast, visibility accuracy, accuracy of the differential phase, of the closure-phase and of the differential visibility. It also provides results of the first tests on sky and the planning of the on-going commissioning.
We report on a database service that allows users to query calibrated optical interferometry data (OIFITS format) as well as regularly-updated observation logs obtained with a wide range of interferometric instruments. It widely uses Virtual Observatory tools to increase diffusion and operability. In this contribution, we present the characteristics and functionalities of the first global optical interferometry archive service.
Observing reference stars with a known diameter is almost the only possibility to calibrate optical interferometry observations. The JMMC Calibrator Workgroup develops methods to ascertain the angular diameter of stars since 2000 and provides this expertise in the SearchCal software and associated databases. We provide on a regularly basis the JSDC, a catalogue of such stars, and an open access to our server that dynamically finds calibrators near science objects by querying CDS hosted catalogs. Here we propose a novel approach in the estimation of angular stellar diameters based on observational quantities only. It bypasses the knowledge of the visual extinction and intrinsic colors, thanks to the use of absorption free pseudo-colors (AFC) and the spectral type number on the x-axis. This new methodology allows to compute the angular diameter of 443 703 stars with a relative precision of about 1%. This calibrator set will become after filtering the next JSDC release.
This poster advertizes the Jean-Marie Mariotti Center software tools, databases and services aimed at facilitating the use of optical interferometry worldwide such as preparation of observations, data reduction and data analysis. Its mission and organization are presented before listing the current software suite. Finally some facts and perspectives are mentioned.
We present the third release of the AMBER data reduction software by the JMMC. This software is based on
core algorithms optimized after several years of operation. An optional graphic interface in a high level language
allows the user to control the process step by step or in a completely automatic manner. Ongoing improvement
is the implementation of a robust calibration scheme, making use of the full calibration sets available during
the night. The output products are standard OI-FITS files, which can be used directly in high level software
like model fitting or image reconstruction tools. The software performances are illustrated on a full data set of
calibrators observed with AMBER during 5 years taken in various instrumental setup.
The JMMC1 Calibrator Workgroup has long developed methods to ascertain the angular diameter of stars, and provides
this expertise in the SearchCal2 software. SearchCal dynamically finds calibrators near science objects by querying CDS3
hosted catalogs according to observational parameters. Initially limited to bright objects (K magnitude ≤ 5.5), it has been
upgraded with a new method providing calibrators without any magnitude limit but those of queried catalogs. We
introduce here a new static catalog of stellar diameters, containing more than 38000 entries, obtained from SearchCal
results aggregation on the whole celestial sphere, complete for all stars with HIPPARCOS4 parallaxes. We detail the
methods and tools used to produce and study this catalog, and compare the static catalog approach with the dynamical
querying provided by SearchCal engine. We also introduce a new Virtual Observatory service, enabling the reporting of,
and querying about, stars flagged as "bad calibrators" by astronomers, adding this ever-growing database to our
In this paper we compare the performance of multi and single-mode
interferometry for the estimation of the phase of the complex
visibility in presence of detector, photon and atmospheric noises. We show that, despite the loss of flux
occurring when injecting the light in the single-mode component, the spatial
filtering properties of such single-mode devices often enable
higher performance than multimode concepts. In
the high flux regime speckle noise dominated,
single-mode interferometry is always more efficient, and its performance is
significantly better when the correction provided
by adaptive optics becomes poor, by a factor of 2 and more when the Strehl
ratio is lower than 10%. In detector noise regime, multimode interferometry reaches better performance, yet the gain never exceeds 20%, which corresponds to the percentage of photon loss due to the injection in the guides.
We finally show that
single-mode interferometry is also more robust to the turbulence
in both cases of fringe tracking and phase referencing, at the exception of narrow field of views. We conclude that fringe trackers built using single-mode optics should be considered as a solution both practical and competitive.
We present here a new observational technique, Phase Closure Nulling (PCN), which has the potential to obtain
very high contrast detection and spectroscopy of faint companions to bright stars. PCN consists in measuring
closure phases of fully resolved objects with a baseline triplet where one of the baselines crosses a null of the
object visibility function. For scenes dominated by the presence of a stellar disk, the correlated flux of the star
around nulls is essentially canceled out, and in these regions the signature of fainter, unresolved, scene object(s)
dominates the imaginary part of the visibility in particular the closure phase. We present here the basics of the
PCN method, the initial proof-of-concept observation, the envisioned science cases and report about the first
observing campaign made on VLTI/AMBER and CHARA/MIRC using this technique.
The VLTI Spectro Imager project aims to perform imaging with a temporal resolution of 1 night and with a maximum
angular resolution of 1 milliarcsecond, making best use of the Very Large Telescope Interferometer capabilities. To
fulfill the scientific goals (see Garcia et. al.), the system requirements are: a) combining 4 to 6 beams; b) working in
spectral bands J, H and K; c) spectral resolution from R= 100 to 12000; and d) internal fringe tracking on-axis, or off-axis
when associated to the PRIMA dual-beam facility.
The concept of VSI consists on 6 sub-systems: a common path distributing the light between the fringe tracker and the
scientific instrument, the fringe tracker ensuring the co-phasing of the array, the scientific instrument delivering the
interferometric observables and a calibration tool providing sources for internal alignment and interferometric
calibrations. The two remaining sub-systems are the control system and the observation support software dedicated to the
reduction of the interferometric data.
This paper presents the global concept of VSI science path including the common path, the scientific instrument and the
calibration tool. The scientific combination using a set of integrated optics multi-way beam combiners to provide high-stability
visibility and closure phase measurements are also described. Finally we will address the performance budget of
the global VSI instrument. The fringe tracker and scientific spectrograph will be shortly described.
The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer
providing the ESO community with spectrally-resolved, near-infrared images at angular resolutions
down to 1.1 milliarcsecond and spectral resolutions up to R = 12000. Targets as faint as K = 13 will be imaged
without requiring a brighter nearby reference object; fainter targets can be accessed if a suitable reference is
available. The unique combination of high-dynamic-range imaging at high angular resolution and high spectral
resolution enables a scientific program which serves a broad user community and at the same time provides the
opportunity for breakthroughs in many areas of astrophysics. The high level specifications of the instrument are
derived from a detailed science case based on the capability to obtain, for the first time, milliarcsecond-resolution
images of a wide range of targets including: probing the initial conditions for planet formation in the AU-scale
environments of young stars; imaging convective cells and other phenomena on the surfaces of stars; mapping
the chemical and physical environments of evolved stars, stellar remnants, and stellar winds; and disentangling the central regions of active galactic nuclei and supermassive black holes. VSI will provide these new capabilities
using technologies which have been extensively tested in the past and VSI requires little in terms of new
infrastructure on the VLTI. At the same time, VSI will be able to make maximum use of new infrastructure as it
becomes available; for example, by combining 4, 6 and eventually 8 telescopes, enabling rapid imaging through
the measurement of up to 28 visibilities in every wavelength channel within a few minutes. The current studies
are focused on a 4-telescope version with an upgrade to a 6-telescope one. The instrument contains its own
fringe tracker and tip-tilt control in order to reduce the constraints on the VLTI infrastructure and maximize
the scientific return.
We present here the general formalism and data processing steps used in the data reduction pipeline of the AMBER instrument. AMBER is a three-telescope interferometric beam combiner in J, H and K bands installed at ESO's Very Large Telescope Interferometer. The fringes obtained on the 3 pairs of telescopes are spatially coded and spectrally dispersed. These are monitored on a 512x512 infrared camera at frame rates up to 100 frames per second, and this paper presents the algorithm used to retrieve the complex coherent visibility of the science target and the subsequent squared visibility, differential phase and phase closure on the 3 bases and in the 3 spectral bands available in AMBER.
Since several years, long baseline infrared interferometry succeeds in
providing handful of astrophysical results from model fitting of the visibility measurements alone. Continuing on these encouraging results, and thanks to the development of elaborated recombination scheme which allow to gather stellar light coming from 3 telescopes or more, recent (IOTA/IONIC, NPOI) and new (VLTI/AMBER) interferometers have also access to closure phase measurements as well as to a better (u,v) coverage. When the (u,v) coverage is still insufficient to perform image reconstruction. a least square fit approach is required, taking benefit of the closure phases together with visibility informations. Within this framework, and in the light of the AMBER experiment, we simulate realistic observations of star-planet systems. Computing the statistics of the observables, and then characterizing the performances of this instrument, we investigate the potential of AMBER to detect Jovian planets around sun-like stars
by computing Signal to Noise Ratio on the constrained parameters, i.e. the flux ratio and the separation. We focus here on the specific system sun-planet, knowing that the general case will be treated in a forthcoming paper. We particularly study how important is the contribution of the closure phase in the model-fitting process, relatively to the visibility.
The science objectives of VITRUV is to investigate the morphology of compact astrophysical objects in optical wavelengths like the environment of AGN, star forming regions, stellar surfaces. This instrument will take full advantage of the VLTI site with 4 very large telescopes and 4 auxiliary telescopes. The instrument concept is to built aperture synthesis images like the millimeter-wave radiointerferometer of the IRAM Plateau de Bure. VITRUV coupled to the VLTI will have similar and even better resolution than ALMA. The astrophysical specifications although not yet finalized will be a temporal resolution of the order of 1 day, spectral resolution from 100 to 30,000, image dynamic from 100 to 1,000, a field of view of 1 arcsec for an initial wavlength coverage from 1 to 2.5 microns that could be extended from 0.5 to 5 microns. The technology that is contemplated at this stage is integrated optics.
Interferometry beam combiners that use optical waveguides, i.e. optical fibers or integrated optics, become popular in optical interferometry because of their flexibility, but also in the case of single-mode waveguide because of their properties of spatial filtering that increases the accuracy of interferometric measurement in an atmosphere-perturbed environment. However we know very little
about the way the electric field propagates and even less about the
correlation between the different beams of an optical interferometer. In this paper, we present in this paper an analysis of single mode optical waveguides in the framework of stellar interferometry. We first analyze the output electric field using
radiated modes and show that the rejection rate we can derive in the
case of nulling interferometry depends on many parameters, including the flux integration radius and the force of the aberrations. Secondly, since the interferometric equation can be interpreted in terms of carrying wave that carries respectively the optical power received by each telescope and the coherent power between two telescopes, we show that the interferometric equation involves a quantity called the modal visibilities which is not equal to the object visibility. The relationship between the two visibilities and the behaviour in the presence of atmosphere are also presented.
The Jean-Marie Mariotti Center is a network of 11 French Institutes,
Laboratories or Observatories, appointed by CNRS in 2000. It coordinates the efforts of the member institutes to offer all the potential users of interferometric facilities the best operational environment, providing software, academic formation and stimulating the prospective on new interferometric developments. At present,
besides academic formation, the major effort is focused on the
development of the software to prepare the observations, to reduce the data and to interpret the results in terms of models or reconstructed images. In this contribution, we describe the achievements and the future plans of the Mariotti Center.
AMBER is the General User near infrared focal instrument of the Very Large Telescope Interferometer. Its a single mode, dispersed fringes, three telescopes instrument. A limiting magnitude of the order of H=13 will allow to tackle a fair sample of extra galactic targets. A very high accuracy, in particular in color differential phase and closure phase modes gives good hope for very high dynamic range observation, possibly including hot extra solar planets. The relatively high maximum spectral resolution, up to 10000, will allow some stellar activity observations. Between this extreme goals, AMBER should have a wide range of applications including Young Stellar Objects, Evolved Stars, circumstellar material and many others. This paper tries to introduce AMBER to its future users with
information on what it measures, how it is calibrated and hopes
to give the readers ideas for applications.
Up until now and with the first generation of the next optical interferometers, only a few telescopes, such as 3 or 4, are enabled for gathering the starlight. In such a case, short night-time observational runs will only provide small number of measured baselines. The lack of spatial frequencies mapped in the uv plane thus prevents from a reconstruction of the studied object. It therefore implies to define an a-priori model and to constraint its parameters from the available measurements. We propose here to fit the model parameters from a least square minimization-type approach. We develop a general formalism that can be applied to the three common interferometric observables. These observables are the square visibility, the closure phase and the differential phase. We also pay attention on the formal analysis of the error on the estimated observables and on the resulting error on the model parameters. This approach allows us to run realistic pre-observational simulations, to estimate the performances of the telescope/recombiner instrument, and to sense the feasibility of the intended observation. We finally apply this theoretical study to the recombiner AMBER on the VLTI when pointing at a single star.
AMBER is a focal instrument for the Very Large Telescope Interferometer working in the near infrared from 1.1 to 2.4 micrometers . It has been designed having in mind the General User of interferometric observations and the full range of his possible astrophysical programs. However the three programs used to define the key specifications have been the study of Young Stellar Objects, the study of Active Galactic Nuclei dust tori and broad line regions and the measure of masses and spectra of hot Extra Solar Planets. AMBER combines up to three beams produced by the VLTI 8 m Unit Telescopes equipped with Adaptive Optics and/or by the 1.8 m Auxiliary Telescopes. The fringes are dispersed with resolutions ranging from 35 to 10000. It is optimized for high accuracy single mode measurements of the absolute visibility, of the variation of the visibility and phase with wavelength (differential interferometry) and of phase closure relations with three telescopes. The instrument and its software are designed to allow a highly automated user friendly operation and an easy maintenance.
Optical fibers are now often used in long baseline interferometry because they offer spatial filtering which leads to better accuracy in presence of atmospheric turbulence. Although this property is now well-known and spatial filtering used at various interferometers (IOTA, PTI, ...) and planned for upcoming facilities (VLTI/AMBER, Keck), the underlying physics of spatial filtering is far from being understood. For example up to now, nobody has been able to theoretically predict in which conditions the use of spatial filters improves the quality of the measures. In this paper, we study the propagation of the light through different spatial filters (pinhole, step index fibers) and given preliminary theoretical prediction for the domain of superiority of spatial filtering. We show that for typical observations in the near-infrared with large telescopes corrected by a 64-actuators adaptive optics system, the spatial filtering always provide a better signal-to-noise ratio than the direct coupling of the light.
We present the method which computes the expected signal-to- noise ratio of the observations carried out by AMBER, the near-infrared focal instrument of the VLTI. We include photon noise, detector read-out noise, thermal noise as well as the instrument OPD stability and Strehl fluctuations. We believe that this algorithm can be extended to any other optical interferometers. The performances are computed in a variety of conditions: size of the apertures (8-m Unit telescopes or 1.8-m Auxiliary telescopes), adaptive optics correction (tip-tilt, 64 actuators), atmospheric conditions (averaged 0.7 arcsecond seeing and excellent 0.5 arcsecond seeing), wavelengths (from the J-band to the K-band), fringe tracking accuracy (from no to perfect fringe tracking), elementary exposure times, spectral resolution (35, 1000 and 10000), off-axis/on-axis operation.
The wavefront correction by an adaptive optics (AO) system is never perfect, but images obtained with AO can be restored by deconvolution methods, if the point spread function is known. We present the first result of PSF reconstruction from the wavefront sensor measurements applied to the AO system ADONIS installed at the 3.6m ESO telescope at La Silla.
Differential speckle interferometry is based on the cross analysis of series of speckle patterns produced in different wavelengths. The study of the position differences between these speckles provides angular information on objects much smaller than the diffraction limit. In order to make the measurements of the photocenter displacement, we have built an instrument which behaves like a spectrograph in one direction and a speckle interferometer in the perpendicular direction. A mirror anamorphoser permits us to meet the different sampling requirements. The dispersed speckle pattern is recorded by a photon counting camera. The measurements of the photocenter displacements are very sensitive to differences of aberration between spectral channels and temporal variations of the detector's distorsion. Our instrument provides images with a quality equal to the diffraction limit plus residual aberrations of the order of one hundreth of the wavelength used. The distorsion of the optics is much smaller than the size of the temporal variations of the detector's distorsion. In order to correct this variable distorsion, spatial and spectral modulations are made in a fully automated instrument.