MATISSE is the second-generation mid-infrared spectrograph and imager for the Very Large Telescope Interferometer (VLTI) at Paranal. This new interferometric instrument will allow significant advances in various fundamental research fields: studying the planet-forming region of disks around young stellar objects, understanding the surface structures and mass loss phenomena affecting evolved stars, and probing the environments of black holes in active galactic nuclei. As a first breakthrough, MATISSE will enlarge the spectral domain of current optical interferometers by offering the L and M bands in addition to the N band. This will open a wide wavelength domain, ranging from 2.8 to 13 μm, exploring angular scales as small as 3 mas (L band) / 10 mas (N band). As a second breakthrough, MATISSE will allow mid-infrared imaging - closure-phase aperture-synthesis imaging - with the four Unit Telescopes (UT) or Auxiliary Telescopes (AT) of the VLTI. Moreover, MATISSE will offer a spectral resolution range from R ~ 30 to R ~ 5000. Here, we remind the concept, the instrumental design, and the main features of MATISSE. We also describe the last months of preparation, the status of the instrument, which was shipped to Cerro Paranal on the site of the ESO Very Large Telescope in October 2017, and the expected schedule for the opening to the community. The instrument is currently in its Commissioning phase. A complementary dedicated article details the Commissioning results, which include the first performance estimates on sky.
MATISSE is the second-generation mid-infrared spectrograph and imager for the Very Large Telescope Interferometer (VLTI) at Paranal. This new interferometric instrument will allow significant advances by opening new avenues in various fundamental research fields: studying the planet-forming region of disks around young stellar objects, understanding the surface structures and mass loss phenomena affecting evolved stars, and probing the environments of black holes in active galactic nuclei. As a first breakthrough, MATISSE will enlarge the spectral domain of current optical interferometers by offering the L and M bands in addition to the N band. This will open a wide wavelength domain, ranging from 2.8 to 13 μm, exploring angular scales as small as 3 mas (L band) / 10 mas (N band). As a second breakthrough, MATISSE will allow mid-infrared imaging - closure-phase aperture-synthesis imaging - with up to four Unit Telescopes (UT) or Auxiliary Telescopes (AT) of the VLTI. Moreover, MATISSE will offer a spectral resolution range from R ∼ 30 to R ∼ 5000. Here, we present one of the main science objectives, the study of protoplanetary disks, that has driven the instrument design and motivated several VLTI upgrades (GRA4MAT and NAOMI). We introduce the physical concept of MATISSE including a description of the signal on the detectors and an evaluation of the expected performances. We also discuss the current status of the MATISSE instrument, which is entering its testing phase, and the foreseen schedule for the next two years that will lead to the first light at Paranal.
MATISSE represents a great opportunity to image the environment around massive and evolved stars. This will allow one to put constraints on the circumstellar structure, on the mass ejection of dust and its reorganization, and on the dust-nature and formation processes. MATISSE measurements will often be pivotal for the understanding of large multiwavelength datasets on the same targets collected through many high-angular resolution facilities at ESO like sub-millimeter interferometry (ALMA), near-infrared adaptive optics (NACO, SPHERE), interferometry (PIONIER, GRAVITY), spectroscopy (CRIRES), and mid-infrared imaging (VISIR). Among main sequence and evolved stars, several cases of interest have been identified that we describe in this paper.
We present an overview of the scientific potential of MATISSE, the Multi Aperture mid-Infrared SpectroScopic Experiment for the Very Large Telescope Interferometer. For this purpose we outline selected case studies from various areas, such as star and planet formation, active galactic nuclei, evolved stars, extrasolar planets, and solar system minor bodies and discuss strategies for the planning and analysis of future MATISSE observations. Moreover, the importance of MATISSE observations in the context of complementary high-angular resolution observations at near-infrared and submillimeter/millimeter wavelengths is highlighted.
MATISSE is the mid-infrared spectrograph and imager for the Very Large Telescope Interferometer (VLTI) at Paranal. This second generation interferometry instrument will open new avenues in the exploration of our Universe. Mid-infrared interferometry with MATISSE will allow significant advances in various fundamental research fields: studies of disks around young stellar objects where planets form and evolve, surface structures and mass loss of stars in late evolutionary stages, and the environments of black holes in active galactic nuclei. MATISSE is a unique instrument. As a first breakthrough it will enlarge the spectral domain used by optical interferometry by offering the L & M bands in addition to the N band, opening a wide wavelength domain, ranging from 2.8 to 13 μm on angular scales of 3 mas (L/M band) / 10 mas (N band). As a second breakthrough, it will allow mid-infrared imaging – closure-phase aperture-synthesis imaging – with up to four Unit Telescopes (UT) or Auxiliary Telescopes (AT) of the VLTI. MATISSE will offer various ranges of spectral resolution between R~30 to ~5000. In this article, we present some of the main science objectives that have driven the instrument design. We introduce the physical concept of MATISSE including a description of the signal on the detectors and an evaluation of the expected performance and discuss the project status. The operations concept will be detailed in a more specific future article, illustrating the observing templates operating the instrument, the data reduction and analysis, and the image reconstruction software.
Claudia Paladini, Daniela Klotz, Stephane Sacuto, Josef Hron, Markus Wittkowski, Eric Lagadec, Tijl Verhoelst, Alain Jorissen, Andrea Richichi, Martin Groenewegen, Hans Olofsson, Franz Kerschbaum
The mass-loss process is a key ingredient for our understanding in many fields of astrophysics, including stellar evolution and the enrichment of the interstellar medium (ISM) via stellar yields. We combined the capability of the VLTI/MIDI and VLT/VISIR instruments with very recent Herschel/PACS observations to characterize the geometry of mass loss from evolved red giants on the Asymptotic Giant Branch (AGB) at various scales. This paper describes the sample of objects, the observing strategy, the tool for the interpretation, and preliminary MIDI results for two targets: U Ant and θ Aps.
KEYWORDS: Visibility, Stars, Error analysis, Data modeling, Interferometry, Geometrical optics, Monte Carlo methods, Physics, Statistical analysis, Black bodies
We developed the tool GEM-FIND that allows to constrain the morphology and brightness distribution of ob-
jects. The software fits geometrical models to spectrally dispersed interferometric visibility measurements in the
N-band using the Levenberg-Marquardt minimization method. Each geometrical model describes the bright-
ness distribution of the object in the Fourier space using a set of wavelength-independent and/or wavelength-
dependent parameters. In this contribution we numerically analyze the stability of our nonlinear fitting approach
by applying it to sets of synthetic visibilities with statistically applied errors, answering the following questions:
How stable is the parameter determination with respect to (i) the number of uv-points, (ii) the distribution of
points in the uv-plane, (iii) the noise level of the observations?
MATISSE is a mid-infrared spectro-interferometer combining the beams of up to four Unit Telescopes or Auxiliary
Telescopes of the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory.
MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. New characteristics present in
MATISSE will give access to the mapping and the distribution of the material, the gas and essentially the dust, in the
circumstellar environments by using the mid-infrared band coverage extended to L, M and N spectral bands. The four
beam combination of MATISSE provides an efficient uv-coverage: 6 visibility points are measured in one set and 4
closure phase relations which can provide aperture synthesis images in the mid-infrared spectral regime.
We give an overview of the instrument including the expected performances and a view of the Science Case. We present
how the instrument would be operated. The project involves the collaborations of several agencies and institutes: the
Observatoire de la Côte d’Azur of Nice and the INSU-CNRS in Paris, the Max Planck Institut für Astronomie of
Heidelberg; the University of Leiden and the NOVA-ASTRON Institute of Dwingeloo, the Max Planck Institut für
Radioastronomie of Bonn, the Institut für Theoretische Physik und Astrophysik of Kiel, the Vienna University and the
Konkoly Observatory.
One of the aims of next generation optical interferometric instrumentation is to be able to make use of information
contained in the visibility phase to construct high dynamic range images.
Radio and optical interferometry are at the two extremes of phase corruption by the atmosphere. While in
radio it is possible to obtain calibrated phases for the science objects, in the optical this is currently not possible.
Instead, optical interferometry has relied on closure phase techniques to produce images. Such techniques allow
only to achieve modest dynamic ranges. However, with high contrast objects, for faint targets or when structure
detail is needed, phase referencing techniques as used in radio interferometry, should theoretically achieve higher
dynamic ranges for the same number of telescopes.
Our approach is not to provide evidence either for or against the hypothesis that phase referenced imaging
gives better dynamic range than closure phase imaging. Instead we wish to explore the potential of this technique
for future optical interferometry and also because image reconstruction in the optical using phase referencing
techniques has only been performed with limited success.
We have generated simulated, noisy, complex visibility data, analogous to the signal produced in radio interferometers,
using the VLTI as a template. We proceeded with image reconstruction using the radio image
reconstruction algorithms contained in aips imagr (clean algorithm). Our results show that image reconstruction
is successful in most of our science cases, yielding images with a 4 milliarcsecond resolution in K band.
We have also investigated the number of target candidates for optical phase referencing. Using the 2MASS
point source catalog, we show that there are several hundred objects with phase reference sources less than 30
arcseconds away, allowing to apply this technique.
KEYWORDS: Telescopes, Stars, Spectral resolution, Spatial resolution, Interferometry, Integrated optics, Space telescopes, Visibility, Image restoration, Signal to noise ratio
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 the work developed within the science team of the Very Large Telescope Interferometer Spectro-Imager (VSI) during the Phase A studies. VSI aims at delivering ~ 1 milliarcsecond resolution data cubes
in the near-infrared, with several spectral resolutions up to 12 000, by combining up to 8 VLTI telescopes. In
the design of an instrument, the science case plays a central role by supporting the instrument construction
decision, defining the top-level requirements and balancing design options. The overall science philosophy of
VSI was that of a general user instrument serving a broad community. The science team addressed themes
which included several areas of astrophysics and illustrated specific modes of operation of the instrument: a)
YSO disks and winds; b) Multiplicity of young stars; c) Exoplanets; d) Debris disks; e) Stellar surface imaging;
f) The environments of evolved stars; g) AGN tori; h) AGN's Broad Line Region; i) Supermassive black-holes;
and j) Microlensing. The main conclusions can be summarized as follows: a) The accessible targets and related
science are extremely sensitive to the instrument limiting magnitude; the instrument should be optimized for
sensitivity and have its own fringe tracker. b) Most of the science cases are readily achievable with on-axis fringe
tracking, off-axis fringe tracking enabling extra science. c) In most targets (YSOs, evolved stars and AGNs), the
interpretation and analysis of circumstellar/nuclear dust morphology requires direct access to the gas via spectral
resolved studies of emission lines, requiring at least a spectral resolution of 2 500. d) To routinely deliver images
at the required sensitivity, the number of telescopes in determinant, with 6 telescopes being favored. e) The
factorial increase in the number of closure phases and visibilities, gained in a single observation, makes massive
surveys of parameters and related science for the first time possible. f) High dynamic range imaging and very
high dynamic range differential closure phase are possible allowing the study of debris disks and characterization
of pegasides. g) Spectro-imaging in the near-infrared is highly complementary to ALMA, adaptive optics and
interferometric imaging in the thermal infrared.
MATISSE is foreseen as a mid-infrared spectro-interferometer combining the beams of up to four UTs/ATs of the Very
Large Telescope Interferometer (VLTI) of the European Southern Observatory. The related science case study
demonstrates the enormous capability of a new generation mid-infrared beam combiner.
MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. MIDI is a very successful
instrument which offers a perfect combination of spectral and angular resolution. New characteristics present in
MATISSE will give access to the mapping and the distribution of the material (typically dust) in the circumstellar
environments by using a wide mid-infrared band coverage extended to L, M and N spectral bands. The four beam
combination of MATISSE provides an efficient UV-coverage : 6 visibility points are measured in one set and 4 closure
phase relations which can provide aperture synthesis images in the mid-infrared spectral regime.
Classically, optical and near-infrared interferometry have relied on closure phase techniques to produce images.
Such techniques allow us to achieve modest dynamic ranges.
In order to test the feasibility of next generation optical interferometers in the context of the VLTI-spectro-imager
(VSI), we have embarked on a study of image reconstruction and analysis. Our main aim was to test the
influence of the number of telescopes, observing nights and distribution of the visibility points on the quality of
the reconstructed images. Our results show that observations using six Auxiliary Telescopes (ATs) during one
complete night yield the best results in general and is critical in most science cases; the number of telescopes is
the determining factor in the image reconstruction outcome.
In terms of imaging capabilities, an optical, six telescope VLTI-type configuration and ~200 meter baseline
will achieve 4 mas spatial resolution, which is comparable to ALMA and almost 50 times better than JWST will
achieve at 2.2 microns. Our results show that such an instrument will be capable of imaging, with unprecedented
detail, a plethora of sources, ranging from complex stellar surfaces to microlensing events.
VLTi Spectro-Imager (VSI) is a proposition for a second generation VLTI instrument which is aimed at providing
the ESO community with the capability of performing image synthesis at milli-arcsecond angular resolution. VSI
provides the VLTI with an instrument able to combine 4 telescopes in a baseline version and optionally up to
6 telescopes in the near-infrared spectral domain with moderate to high spectral resolution. The instrument
contains its own fringe tracker in order to relax the constraints onto the VLTI infrastructure. VSI will do
imaging at the milli-arcsecond scale with spectral resolution of: a) the close environments of young stars probing
the initial conditions for planet formation; b) the surfaces of stars; c) the environment of evolved stars, stellar
remnants and stellar winds, and d) the central region of active galactic nuclei and supermassive black holes. The
science cases allowed us to specify the astrophysical requirements of the instrument and to define the necessary
studies of the science group for phase A.
We briefly summarize the status of dynamic model atmospheres for carbon rich red giants and present some recent results of comparisons between synthetic spectra and observations. We then discuss synthetic intensity profiles and visibilities for such stars. In particular, the effects of atmospheric dynamics on different spectral bands and for different model parameters are studied.
TIMMI2 ESO's 2nd generation Thermal Infrared Multimode Instrument had astronomical first light in October 2000 at the 3.6 m telescope on La Silla, Chile. Since February 2001 it is in regular use, both by visiting astronomers and in service mode, typically one third of the total telescope time. Using a Raytheon 240 x 320 pixel As:Si-BIB detector allows imaging and grism spectroscopy between 5 and 24 μm. TIMMI2 has also a linear polarimetry mode. We will give a description of the instrument from technical to operational aspects. Because of the substantial gain in sensitivity as compared to previous generation instruments a new set of infrared calibration standards has been constructed. The instrument and telescope are subject of an ongoing sensitivity monitoring program enabling to improve the sensitivity while allowing to spot the development of problems immediately. For stellar objects the sensitivity 10 σ in 1 hour of telescope time is in the range of 15 - 30 mJy. TIMMI2 at the telescope shows negligible flexure (≤ 0.2") while having basically diffraction limited performance for λ ≥ 8 μm.
TIMMI2 is a focal reducer with variable magnification using a reflective collimator and various camera lenses from Silicon, CdTe, Germanium and KRS-5. The primary operating wavelength is 8-24 microns with limited access also to the 3-5 micron region. Longslit and Echelle spectroscopy up to a resolving power of 1000 are implemented with grisms. A cryogenic wire grid polarizer allows for imaging polarimetry. TIMMI2 uses a 240 X 320 As:Si detector array and is cooled by a 2 stage Gifford-McMahon cooler. Maximum field is 72 X 96 arcsec. TIMMI2 has 5 internal cryogenic functions and one external wheel holding calibration targets. TIMMI2 will be interfaced to the 3.6m telescope with a special IR adapter allowing wheel holding registration of the IR images with respect to astrometric reference frames. The instrument design, electronics and results from laboratory test will be presented. Sensitivity estimates as well as an outlook on possible astronomical programs will be given.
KEYWORDS: Telescopes, Cameras, Control systems, Calibration, Human-machine interfaces, Polarimetry, Electronics, Data processing, Image processing, Video
The new ESU Thermal Infrared Multi-Mode Instrument TIMMI2 is described in detail in Reimann et al. The TNT-Timmi Navigator Terminal is the graphical user interface for TIMMI2. It provides the communication between telescope, instrument and reduction pipeline. The TNT is a very easy way allows the astronomer to prepare and run complex observing programs. The graphical elements are based on Forms Library (A Graphical User Interface Toolkit for X). The TNT is written in C.
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