68 research outputs found
Image quality and high contrast improvements on VLT/NACO
NACO is the famous and versatile diffraction limited NIR imager and
spectrograph with which ESO celebrated 10 years of Adaptive Optics at the VLT.
Since two years a substantial effort has been put in to understanding and
fixing issues that directly affect the image quality and the high contrast
performances of the instrument. Experiments to compensate the non-common-path
aberrations and recover the highest possible Strehl ratios have been carried
out successfully and a plan is hereafter described to perform such measurements
regularly. The drift associated to pupil tracking since 2007 was fixed in
October 2011. NACO is therefore even better suited for high contrast imaging
and can be used with coronagraphic masks in the image plane. Some contrast
measurements are shown and discussed. The work accomplished on NACO will serve
as reference for the next generation instruments on the VLT, especially those
working at the diffraction limit and making use of angular differential imaging
(i.e. SPHERE, VISIR, possibly ERIS).Comment: 14 pages, 5 figures, SPIE 2012 Astronomical Instrumentation
Proceedin
The third version of the AMBER data reduction software
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.Comment: To be published in the proceedings of the SPIE'2010 conference on
"Optical and Infrared Interferometry II
Status and new operation modes of the versatile VLT/NACO
This paper aims at giving an update on the most versatile adaptive optics fed
instrument to date, the well known and successful NACO . Although NACO is only
scheduled for about two more years at the Very Large Telescope (VLT), it keeps
on evolving with additional operation modes bringing original astronomical
results. The high contrast imaging community uses it creatively as a test-bench
for SPHERE and other second generation planet imagers. A new visible wavefront
sensor (WFS) optimized for Laser Guide Star (LGS) operations has been installed
and tested, the cube mode is more and more requested for frame selection on
bright sources, a seeing enhancer mode (no tip/tilt correction) is now offered
to provide full sky coverage and welcome all kind of extragalactic
applications, etc. The Instrument Operations Team (IOT) and Paranal engineers
are currently working hard at maintaining the instrument overall performances
but also at improving them and offering new capabilities, providing the
community with a well tuned and original instrument for the remaining time it
is being used. The present contribution delivers a non-exhaustive overview of
the new modes and experiments that have been carried out in the past months.Comment: 10 pages, 7 figures, SPIE 2010 Astronomical Instrumentation
Proceedin
The VLTI / PIONIER near-infrared interferometric survey of southern T Tauri stars. I. First results
Context : The properties of the inner disks of bright Herbig AeBe stars have
been studied with near infrared (NIR) interferometry and high resolution
spectroscopy. The continuum and a few molecular gas species have been studied
close to the central star; however, sensitivity problems limit direct
information about the inner disks of the fainter T Tauri stars.
Aims : Our aim is to measure some of the properties of the inner regions of
disks surrounding southern T Tauri stars.
Methods : We performed a survey with the PIONIER recombiner instrument at
H-band of 21 T Tauri stars. The baselines used ranged from 11 m to 129 m,
corresponding to a maximum resolution of 3mas (0.45 au at 150 pc).
Results : Thirteen disks are resolved well and the visibility curves are
fully sampled as a function of baseline in the range 45-130 m for these 13
objects. A simple qualitative examination of visibility profiles allows us to
identify a rapid drop-off in the visibilities at short baselines in 8 resolved
disks. This is indicative of a significant contribution from an extended
contribution of light from the disk. We demonstrate that this component is
compatible with scattered light, providing strong support to a prediction made
by Pinte et al. (2008). The amplitude of the drop-off and the amount of dust
thermal emission changes from source to source suggesting that each disk is
different. A by-product of the survey is the identification of a new
milli-arcsec separation binary: WW Cha. Spectroscopic and interferometric data
of AK Sco have also been fitted with a binary and disk model.
Conclusions : Visibility data are reproduced well when thermal emission and
scattering form dust are fully considered. The inner radii measured are
consistent with the expected dust sublimation radii. Modelling of AK Sco
suggests a likely coplanarity between the disk and the binary's orbital planeComment: 19 pages, 11 figure
FFREE: a Fresnel-FRee Experiment for EPICS, the EELT planets imager
The purpose of FFREE - the new optical bench devoted to experiments on
high-contrast imaging at LAOG - consists in the validation of algorithms based
on off-line calibration techniques and adaptive optics (AO) respectively for
the wavefront measurement and its compensation. The aim is the rejection of the
static speckles pattern arising in a focal plane after a diffraction
suppression system (based on apodization or coronagraphy) by wavefront
pre-compensation. To this aim, FFREE has been optimized to minimize Fresnel
propagation over a large near infrared (NIR) bandwidth in a way allowing
efficient rejection up to the AO control radius, it stands then as a
demonstrator for the future implementation of the optics that will be common to
the scientific instrumentation installed on EPICS.Comment: 12 pages, 15 figures, Proceeding 7736120 of the SPIE Conference
"Adaptive Optics Systems II", monday 28 June 2010, San Diego, California, US
Infrared wavefront sensing for adaptive optics assisted Galactic Center observations with the VLT interferometer and GRAVITY: operation and results
This article describes the operation of the near-infrared wavefront sensing
based Adaptive Optics (AO) system CIAO. The Coud\'e Infrared Adaptive Optics
(CIAO) system is a central auxiliary component of the Very Large Telescope
(VLT) interferometer (VLTI). It enables in particular the observations of the
Galactic Center (GC) using the GRAVITY instrument. GRAVITY is a highly
specialized beam combiner, a device that coherently combines the light of the
four 8-m telescopes and finally records interferometric measurements in the
K-band on 6 baselines simultaneously. CIAO compensates for phase disturbances
caused by atmospheric turbulence, which all four 8 m Unit Telescopes (UT)
experience during observation. Each of the four CIAO units generates an almost
diffraction-limited image quality at its UT, which ensures that maximum flux of
the observed stellar object enters the fibers of the GRAVITY beam combiner. We
present CIAO performance data obtained in the first 3 years of operation as a
function of weather conditions. We describe how CIAO is configured and used for
observations with GRAVITY. In addition, we focus on the outstanding features of
the near-infrared sensitive Saphira detector, which is used for the first time
on Paranal, and show how it works as a wavefront sensor detector.Comment: 12 pages, 8 figures, accepted for publication in Instruments (open
access journal from mdpi
The MAORY ICS software architecture
The Multi Conjugate Adaptive Optics RelaY (MAORY) for ESO's Extremely Large Telescope (ELT) is an adaptive optics module offering multi-conjugate (MCAO) and single-conjugate (SCAO) compensation modes. In MCAO, it relies on the use of up to six Laser Guide Stars (LGS) and three Natural Guide Stars (NGS) for atmospheric turbulence sensing and multiple mirrors for correction, providing high Strehl and high sky coverage. In SCAO mode, a single natural source is used as reference, providing better correction but in a smaller field. MAORY will be installed at the Nasmyth focus of the ELT. It will feed the MICADO first-light diffraction limited imager and a future second instrument. MAORY is being built by a Consortium composed by INAF in Italy and IPAG in France and is currently approaching end of phase B. In this paper we describe the preliminary design of the MAORY Instrument Control System Software (ICS SW). We start with an overview of the MAORY module and then describe the general architecture of the MAORY control network and software. We then describe the main software components, with particular emphasis to those managing the NGS and LGS wavefront sensors functions and the AO off-load and secondary loops, and the main interfaces to subsystems and external systems. We then conclude with a description of the software engineering practices adopted for the development of MAORY ICS SW
Design, pointing control, and on-sky performance of the mid-infrared vortex coronagraph for the VLT/NEAR experiment
Vortex coronagraphs have been shown to be a promising avenue for high- contrast imaging in the close-in environment of stars at thermal infrared (IR) wavelengths. They are included in the baseline design of the mid-infrared extremely large telescope imager and spectrograph. To ensure good performance of these coronagraphs, a precise control of the centering of the star image in real time is needed. We previously developed and validated the quadrant analysis of coronagraphic images for tip-tilt sensing estimator (QACITS) pointing estimator to address this issue. While this approach is not wavelength-dependent in theory, it was never implemented for mid-IR observations, which leads to specific challenges and limitations. Here, we present the design of the mid-IR vortex coronagraph for the "new Earths in the α Cen Region (NEAR) experiment with the Very Large Telescope (VLT)/Very Large Telescope imager and spectrometer for the mid-infrared (VISIR) instrument and assess the performance of the QACITS estimator for the centering control of the star image onto the vortex coronagraph. We use simulated data and on-sky data obtained with VLT/VISIR, which was recently upgraded for observations assisted by adaptive optics in the context of the NEAR experiment. We demonstrate that the QACITS-based correction loop is able to control the centering of the star image onto the NEAR vortex coronagraph with a stability down to 0.015 λ / D rms over 4 h in good conditions. These results show that QACITS is a robust approach for precisely controlling in real time the centering of vortex coronagraphs for mid-IR observations.Peer reviewe
NEAR: New Earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)
By adding a dedicated coronagraph, ESO in collaboration with the Breakthrough Initiatives, modifies the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability this instru- ment has. After the VISIR upgrade in 2012, where coronagraphic masks were first added to VISIR, it became evident that coronagraphy at a ground-based 8m-class telescope critically needs adaptive optics, even at wavelengths as long as 10μm. For VISIR, a work-horse observatory facility instrument in normal operations, this is ”easiest” achieved by bringing VISIR as a visiting instrument to the ESO-VLT-UT4 having an adaptive M2. This “visit” enables a meaningful search for Earth-like planets in the habitable zone around both α-Cen1,2. Meaningful here means, achieving a contrast of ≈ 10^(-6) within ≈ 0.8arcsec from the star while maintaining basically the normal sensitivity of VISIR. This should allow to detect a planet twice the diameter of Earth. Key components will be a diffractive coronagraphic mask, the annular groove phase mask (AGPM), optimized for the most sensitive spectral band-pass in the N-band, complemented by a sophisticated apodizer at the level of the Lyot stop. For VISIR noise filtering based on fast chopping is required. A novel internal chopper system will be integrated into the cryostat. This chopper is based on the standard technique from early radio astronomy, conceived by the microwave pioneer Robert Dicke in 1946, which was instrumental for the discovery of the 3K radio background
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