57 research outputs found
MYSTIC: Michigan Young STar Imager at CHARA
We present the design for MYSTIC, the Michigan Young STar Imager at CHARA.
MYSTIC will be a K-band, cryogenic, 6-beam combiner for the Georgia State
University CHARA telescope array. The design follows the image-plane
combination scheme of the MIRC instrument where single-mode fibers bring
starlight into a non-redundant fringe pattern to feed a spectrograph. Beams
will be injected in polarization-maintaining fibers outside the cryogenic dewar
and then be transported through a vacuum feedthrough into the ~220K cold volume
where combination is achieved and the light is dispersed. We will use a C-RED
One camera (First Light Imaging) based on the eAPD SAPHIRA detector to allow
for near-photon-counting performance. We also intend to support a 4-telescope
mode using a leftover integrated optics component designed for the VLTI-GRAVITY
experiment, allowing better sensitivity for the faintest targets. Our primary
science driver motivation is to image disks around young stars in order to
better understand planet formation and how forming planets might influence disk
structures.Comment: Presented at the 2018 SPIE Astronomical Telescopes + Instrumentation,
Austin, Texas, US
Integrated optics for astronomical interferometry - VI. Coupling the light of the VLTI in K band
Our objective is to prove that integrated optics (IO) is not only a good
concept for astronomical interferometry but also a working technique with high
performance. We used the commissioning data obtained with the dedicated K-band
integrated optics two-telescope beam combiner which now replaces the fiber
coupler MONA in the VLTI/VINCI instrument. We characterize the behaviour of
this IO device and compare its properties to other single mode beam combiner
like the previously used MONA fiber coupler. The IO combiner provides a high
optical throughput, a contrast of 89% with a night-to-night stability of a few
percent. Even if a dispersive phase is present, we show that it does not bias
the measured Fourier visibility estimate. An upper limit of 0.005 for the
cross-talk between linear polarization states has been measured. We take
advantage of the intrinsic contrast stability to test a new astronomical
prodecure for calibrating diameters of simple stars by simultaneously fitting
the instrumental contrast and the apparent stellar diameters. This method
reaches an accuracy with diameter errors of the order of previous ones but
without the need of an already known calibrator. These results are an important
step of integrated optics and paves the road to incoming imaging interferometer
projects
VITRUV - Imaging close environments of stars and galaxies with the VLTI at milli-arcsec resolution
The VITRUV project has the objective to deliver milli-arcsecond
spectro-images of the environment of compact sources like young stars, active
galaxies and evolved stars to the community. This instrument of the VLTI second
generation based on the integrated optics technology is able to combine from 4
to 8 beams from the VLT telescopes. Working primarily in the near infrared, it
will provide intermediate to high spectral resolutions and eventually
polarization analysis. This paper summarizes the result from the concept study
led within the Joint Research Activity advanced instruments of the OPTICON
program.Comment: In "The Power of Optical/IR Interferometry: Recent Scientific Results
and 2nd Generation VLTI Instrumentation", Allemagne (2005) in pres
The planar optics phase sensor: a study for the VLTI 2nd generation fringe tracker
In a few years, the second generation instruments of the Very Large Telescope Interferometer (VLTI) will routinely provide observations with 4 to 6 telescopes simultaneously. To reach their ultimate performance, they will need a fringe sensor capable to measure in real time the randomly varying optical paths differences. A collaboration between LAOG (PI institute), IAGL, OCA and GIPSA-Lab has proposed the Planar Optics Phase Sensor concept to ESO for the 2[SUP]nd[/SUP] Generation Fringe Tracker. This concept is based on the integrated optics technologies, enabling the conception of extremely compact interferometric instruments naturally providing single-mode spatial filtering. It allows operations with 4 and 6 telescopes by measuring the fringes position thanks to a spectrally dispersed ABCD method. We present here the main analysis which led to the current concept as well as the expected on-sky performance and the proposed design
VSI: a milli-arcsec spectro-imager for the VLTI
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.Comment: 12 page
Increasing the imaging capabilities of the VLTI using integrated optics
Several scientific topics linked to the observation of extended structures around astrophysical sources (dust torus around AGN, disks around young stars, envelopes around AGBs) require imaging capability with milli-arcsecond spatial resolution. The current VLTI instruments, AMBER and MIDI, will provide in the coming months the required high angular resolution, yet without actual imaging. As a rule of thumb, the image quality accessible with an optical interferometer is directly related to the number of telescopes used simultaneously: the more the apertures, the better and the faster the reconstruction of the image. We propose an instrument concept to achieve interferometric combination of N telescopes (4 ≤ N ≤ 8) thanks to planar optics technology: 4 x 8-m telescopes in the short term and/or 8 x 1.8-m telescopes in the long term. The foreseen image reconstruction quality in the visible and/or in the near infrared will be equivalent to the one achieved with millimeter radio interferometers. Achievable spatial resolution will be better than the one foreseen with ALMA. This instrument would be able to acquire routinely 1 mas resolution images. A 13 to 20 magnitude sensitivity in spectral ranges from 0.6 to 2.5 μm is expected depending on the choice of the phase referencing guide source. High dynamic range, even on faint objects, is achievable thanks to the high accuracy provided by integrated optics for visibility amplitude and phase measurements. Based on recent validations of integrated optics presented here an imaging instrument concept can be proposed. The results obtained using the VLTI facilities give a demonstration of the potential of the proposed technique
Increasing the imaging capabilities of the VLTI using integrated optics
Several scientific topics linked to the observation of extended structures around astrophysical sources (dust torus around AGN, disks around young stars, envelopes around AGBs) require imaging capability with milli-arcsecond spatial resolution. The current VLTI instruments, AMBER and MIDI, will provide in the coming months the required high angular resolution, yet without actual imaging. As a rule of thumb, the image quality accessible with an optical interferometer is directly related to the number of telescopes used simultaneously: the more the apertures, the better and the faster the reconstruction of the image. We propose an instrument concept to achieve interferometric combination of N telescopes (4 ≤ N ≤ 8) thanks to planar optics technology: 4 x 8-m telescopes in the short term and/or 8 x 1.8-m telescopes in the long term. The foreseen image reconstruction quality in the visible and/or in the near infrared will be equivalent to the one achieved with millimeter radio interferometers. Achievable spatial resolution will be better than the one foreseen with ALMA. This instrument would be able to acquire routinely 1 mas resolution images. A 13 to 20 magnitude sensitivity in spectral ranges from 0.6 to 2.5 μm is expected depending on the choice of the phase referencing guide source. High dynamic range, even on faint objects, is achievable thanks to the high accuracy provided by integrated optics for visibility amplitude and phase measurements. Based on recent validations of integrated optics presented here an imaging instrument concept can be proposed. The results obtained using the VLTI facilities give a demonstration of the potential of the proposed technique
GRAVITY: observing the universe in motion
GRAVITY is the second generation VeryLarge Telescope Interferometer instrument for precision narrow-angle as -trometry and interferometric imaging.With its fibre-fed integrated optics,wavefront sensors, fringe tracker, beamstabilisation and a novel metrologyconcept, GRAVITY will push the sensitivity and accuracy of astrometry andinterferometric imaging far beyond whatis offered today. Providing precisionastrometry of order 10 microarcseconds,and imaging with 4-milliarcsecondresolution, GRAVITY will revolutionisedynamical measurements of celestialobjects: it will probe physics close tothe event horizon of the Galactic Centreblack hole; unambiguously detect andmeasure the masses of black holesin massive star clusters throughout theMilky Way; uncover the details of massaccretion and jets in young stellarobjects and active galactic nuclei; andprobe the motion of binary stars, exoplanets and young stellar discs. Theinstrument capabilities of GRAVITY areoutlined and the science opportunitiesthat will open up are summarised
The MAORY laser guide star wavefront sensor: design status
MAORY will be the multi-adaptive optics module feeding the high resolution camera and spectrograph MICADO at the Extremely Large Telescope (ELT) first light. In order to ensure high and homogeneous image quality over the MICADO field of view and high sky coverage, the baseline is to operate wavefront sensing using six Sodium Laser Guide Stars. The Laser Guide Star Wavefront Sensor (LGS WFS) is the MAORY sub-system devoted to real-time measurement of the high order wavefront distortions. In this paper we describe the MAORY LGS WFS current design, including opto-mechanics, trade-offs and possible future improvements
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