LINC-NIRVANA (LN) is the near-infrared, Fizeau-type imaging interferometer for the large binocular telescope (LBT) on Mt. Graham, Arizona (elevation of 3267 m). The instrument is currently being built by a consortium of German and Italian institutes under the leadership of the Max Planck Institute for Astronomy in Heidelberg, Germany. It will combine the radiation from both 8.4 m primary mirrors of LBT in such a way that the sensitivity of a 11.9 m telescope and the spatial resolution of a 22.8 m telescope will be obtained within a 10.5×10.5 arcsec 2 scientific field of view. Interferometric fringes of the combined beams are tracked in an oval field with diameters of 1 and 1.5 arcmin. In addition, both incoming beams are individually corrected by LN’s multiconjugate adaptive optics system to reduce atmospheric image distortion over a circular field of up to 6 arcmin in diameter. A comprehensive technical overview of the instrument is presented, comprising the detailed design of LN’s four major systems for interferometric imaging and fringe tracking, both in the near infrared range of 1 to 2.4 μm, as well as atmospheric turbulence correction at two altitudes, both in the visible range of 0.6 to 0.9 μm. The resulting performance capabilities and a short outlook of some of the major science goals will be presented. In addition, the roadmap for the related assembly, integration, and verification process are discussed. To avoid late interface-related risks, strategies for early hardware as well as software interactions with the telescope have been elaborated. The goal is to ship LN to the LBT in 2014.
LINC-NIRVANA (LN) is the near-infrared, Fizeau-type imaging interferometer for the Large Binocular Telescope
(LBT) on Mt. Graham, Arizona, USA (3267m of elevation). The instrument is currently being built by a consortium of
German and Italian institutes under the leadership of the Max Planck Institute for Astronomy (MPIA) in Heidelberg,
Germany. It will combine the radiation from both 8.4m primary mirrors of LBT in such a way that the sensitivity of a
11.9m telescope and the spatial resolution of a 22.8m telescope will be obtained within a 10.5arcsec x 10.5arcsec
scientific field of view. Interferometric fringes of the combined beams are tracked in an oval field with diameters of 1
and 1.5arcmin. In addition, both incoming beams are individually corrected by LN’s multi-conjugate adaptive optics
(MCAO) system to reduce atmospheric image distortion over a circular field of up to 6arcmin in diameter.
This paper gives a comprehensive technical overview of the instrument comprising the detailed design of LN’s four
major systems for interferometric imaging and fringe tracking, both in the NIR range of 1 - 2.4μm, as well as
atmospheric turbulence correction at two altitudes, both in the visible range of 0.6 - 0.9μm. The resulting performance
capabilities and a short outlook of some of the major science goals will be presented. In addition, the roadmap for the
related assembly, integration and verification (AIV) process will be discussed. To avoid late interface-related risks,
strategies for early hardware as well as software interactions with the telescope have been elaborated. The goal is to ship
LN to the LBT in 2014.
LINC-NIRVANA is a near infrared interferometric imager with a pair of layer-oriented multi-conjugate adaptive
optics systems (ground layer and high layer) for the Large Binocular Telescope. To prepare for the commissioning
of LINC-NIRVANA, we have integrated the high layer wavefront sensor and its associated deformable mirror (a
Xinetics-349) in a laboratory, located at Max Planck Institute for Astronomy, in Heidelberg, Germany. Together
with a telescope simulator, which includes a rotating field and phase screens that introduce the effects of the
atmosphere, we tested the acquisition of multiple guide stars, calibrating the system with the push-pull method,
and characterizing the wavefront sensor together with the deformable mirror. We have closed the AO loop with
up to 200 Zernike modes and with multiple guide stars. The AO correction demonstrated that uniform correction
can be achieved in a large field of view. We report the current status and results of the experiment.
LINC-NIRVANA is the Fizeau beam combiner for the LBT, with the aim to retrieve the sensitivity of a 12m telescope
and the spatial resolution of a 22.8m one. Despite being only one of the four wavefront sensors of a layer-oriented
MCAO system, the GWS, which is retrieving the deformation introduced by the lower atmosphere, known to be the main
aberration source, reveals a noticeable internal opto-mechanical complexity.
The presence of 12 small devices used to select up to the same number of NGSs, with 3 optical components each,
moving in a wide annular 2'-6' arcmin Field of View and sending the light to a common pupil re-imager, and the need to
obtain and keep a very good super-imposition of the pupil images on the CCD camera, led to an overall alignment
procedure in which more than a hundred of degrees of freedom have to be contemporary adjusted.
The rotation of the entire WFS to compensate for the sky movement, moreover, introduces a further difficulty both in the
alignment and in ensuring the required pupil superposition stability.
A detailed description of the alignment procedure is presented here, together with the lessons learned managing the
complexity of such a WFS, which led to considerations regarding future instruments, like a possible review of numerical
versus optical co-add approach, above all if close to zero read-out noise detectors will be soon available.
Nevertheless, the GWS AIV has been carried out and the system will be soon mounted at LBT to perform what is called
the Pathfinder experiment, which consists in ground-layer correction, taking advantage of the Adaptive Secondary
deformable Mirror.
LINC-NIRVANA will employ four wave front sensors to realize multi-conjugate correction on both arms of a Fizeau interferometer for LBT. Of these, one of the two ground-layer wave front sensors, together with its infrared test camera, comprise a stand-alone test platform for LINC-NIRVANA. Pathfinder is a testbed for full LINC-NIRVANA intended to identify potential interface problems early in the game, thus reducing both technical, and schedule, risk. Pathfinder will combine light from multiple guide stars, with a pyramid sensor dedicated to each star, to achieve ground-layer AO correction via an adaptive secondary: the 672-actuator thin shell at the LBT. The ability to achieve sky coverage by optically coadding light from multiple stars has been previously demonstrated; and the ability to achieve correction with an adaptive secondary has also been previously demonstrated. Pathfinder will be the first system at LBT to combine both of these capabilities.
Since reporting our progress at A04ELT2, we have advanced the project in three key areas: definition of specific goals for Pathfinder tests at LBT, more detail in the software design and planning, and calibration. We report on our progress and future plans in these three areas, and on the project overall.
The atmospheric piston simulator is an integral part of the calibration unit of LINC-NIRVANA, the Fizeau
interferometric imager for the Large Binocular Telescope. The calibration unit will be necessary to align and set
up the different opto - mechanical subsystems of the instrument. It will assist in (1) the alignment of the optics
via reference fibers; (2) establishing zero optical path difference using a balanced fiber splitter; (3) flat fielding of
the detectors with an integrating sphere; (4) correction of the non-common path aberrations using a fiber-based
phase diversity source; and (5) calibration of the adaptive optics with a rotating reference fiber plate. Substantial
testing and verification of the fringe tracker under as realistic as possible conditions in the lab is desirable, since
the performance of the fringe tracker will ultimately determine the high angular resolution imaging capability
of LINC-NIRVANA as a whole. We are therefore also constructing an atmospheric piston simulator working in
the J and H photometric bands. As with many of the other calibration unit sub-systems, our design concept
is mainly fiber based. Opto - electronic phase modulators will be used to introduce the piston sequences. The
control system of the piston modulators will allow for easy implementation of different vibration power spectra.
This will enable us to test and demonstrate the capabilities of the fringe tracker under realistic conditions.
The LINC-NIRVANA wavefront sensors are in their AIT phase. The first Ground-layerWavefront Sensor (GWS)
is shaping in the Adaptive Optics laboratory of the Astronomical Observatory of Padova, while both the Mid-
High Wavefront Sensors (MHWSs) have been aligned and tested as stand-alone units in the Observatory of
Bologna (MHWS#1 aligned to LINC-NIRVANA post focal relay optics).
LINC-NIRVANA is a Fizeau infrared interferometer equipped with advanced, MultiConjugated Adaptive
Optics (MCAO) for the Large Binocular Telescope. The aim of the instrument is to allow true interferometric
imagery over a 10" square Field of View (FoV), getting the sensitivity of a 12m telescope and the spatial resolution
of a 22.8m one. Thanks to the MCAO concept, LINC-NIRVANA will use up to 20 Natural Guide Stars (NGS)
which are divided, according to Layer-Oriented Multiple Field of View technique, between the GWSs and the
MHWSs. To find such a large number of references, the AO systems will use a wide FoV of 6' in diameter and
the light coming from the references used by each WFS will optically sum on its CCD camera.
The MHWSs will detect the deformations due to the high layers and will select up to 8 NGSs in the inner 2'
FoV.
The GWSs, instead, will reconstruct the deformations introduced by the lower atmosphere, which was found
out to be the main source of seeing. Their peculiarity is the highest number of references (up to 12) ever used
in a single instrument, selected in an annular 2'-6' FoV.
LINC-NIRVANA is the IR Fizeau interferometric imager that will be installed within a couple of years on the Large
Binocular Telescope (LBT) in Arizona. Here we present a particular sub-system, the so-called Patrol Camera (PC),
which has been now completed, along with the results of the laboratory tests. It images (in the range 600-900 nm) the
same 2 arcmin FoV seen by the Medium-High Wavefront Sensor (MHWS), adequately sampled to provide the MHWS
star enlargers with the positions of the FoV stars with an accuracy of 0.1 arcsec. To this aim a diffraction-limited
performance is not required, while a distortion free focal plane is needed to provide a suitable astrometric output. Two
identical systems have been realized, one for each single arm, which corresponds to each single telescope. We give here
the details concerning the optical and mechanical layout, as well as the CCD and the control system. The interfaces (mainly software procedures) with LINC-NIRVANA (L-N) are also presented.
Laboratory and on-sky experience suggests that the integration of big astronomical instruments, specially of a
complex interferometric system, is a challenging process. LINC-NIRVANA is the Fizeau interferometric imager
for the Large Binocular Telescope (LBT). Simulating the final operating environment of every system component
has shown how critical is the presence of flexures, vibrations and thermal expansion. Assembling and aligning
the opto-mechanical sub-systems will require an absolute reference which is not affected by static displacements
or positioning errors.
A multi-purpose calibration unit has been designed to ensure the quality of the alignment of optics and
detectors and the reliability of the mechanical setup. This new compact and light-weighted unit is characterized
by sophisticated kinematics, simple mechanical design and composite materials. In addition, the reduced number
of motorized axis improves the stiffness and lowers the angular displacements due to moving parts. The modular
concept integrates several light sources to provide the proper calibration reference for the different sub-systems
of LINC-NIRVANA. For the standard alignment of the optics an absolute reference fiber will be used. For flatfielding
of the detectors the unit provides an integrating sphere, and a special rotating multi-fiber plate (infrared
and visible) is used to calibrate the advanced adaptive optics and the fringe-tracking systems. A module to
control non-common path aberrations (Flattening of Deformable Mirrors) is also provided.
We present in this paper the status of the calibration unit for the interferometric infrared imager LINC-NIRVANA
that will be installed on the Large Binocular Telescope, Arizona. LINC-NIRVANA will combine high angular
resolution (~10 mas in J), and wide field-of-view (up to 2'×2') thanks to the conjunct use of interferometry
and MCAO. The goal of the calibration unit is to provide calibration tools for the different sub-systems of the
instrument. We give an overview of the different tasks that are foreseen as well as of the preliminary detailed
design. We show some interferometric results obtained with specific fiber splitters optimized for LINC-NIRVANA.
The different components of the calibration unit will be used either during the integration phase on site, or during
the science exploitation phase of the instrument.
LINC-NIRVANA is an infrared camera that will work in Fizeau interferometric way at the Large Binocular Telescope
(LBT). It will take advantage of a field corrected from two MCAO systems, one for each arm, based on the Layer
Oriented Technique and using solely Natural Guide Stars. For each arm, there will be two wavefront sensors, one
conjugated to the Ground and one conjugated to a selectable altitude, ranging from 4 to 15 Km. They will explore
different fields of view for the wavefront sensing operations, accordingly to the Multiple Field of View concept, and
particularly the inner 2 arcminutes FoV will be used to select the references for the high layer wavefront sensor while the
ground one will explore a wider anular field, going from 2 to 6 arcminutes in diameter. The wavefront sensors are under
INAF responsibility, and their construction is ongoing in different italian observatories. Here we report on progress, and
particularly on the test ongoing in Padova observatory on the Ground Layer Wavefront Sensor.
LINC-NIRVANA is an infrared camera working in Fizeau interferometric mode. The beams coming from the two
primary mirrors of the LBT are corrected for the effects of the atmospheric turbulence by two Multi-Conjugate Adaptive
Optics (MCAO) systems, working in a scientific field of view of 2 arcminutes. One single arm MCAO system includes
two wave-front sensors, driving two deformable mirrors, one for the ground layer correction (LBT secondary mirror)
and one for the correction of a mid-high layer (up to a maximum distance of 15 km). The first of the two Mid-High
Wavefront Sensors (MHWS) was integrated and tested as a stand-alone unit in the laboratory at INAF-Osservatorio
Astronomico di Bologna, where the telescope was simulated by means of a simple afocal system illuminated by a set of
optical fibers. Then the module was delivered to the MPIA laboratories in Heidelberg, where is going to be integrated
and aligned to the post-focal optical relay of one LINC-NIRVANA arm, including the deformable mirror. A number of
tests are in progress at the moment of this writing, in order to characterize and optimize the system functionalities and
performance. A report is presented about the status of this work.
Following a warm launch in 2013 the MIRI instrument aboard JWST will be operated for a lifetime of 5-10 years in the L2-orbit at a temperature of ~6 K. The main requirements for its three wheel mechanisms include: (1) reliability, (2) optical precision, (3) low power dissipation, (4) high vibration capability, (5) functionality at 4 < T < 300 K. The filter wheel carries broad and narrow band spectral filters, coronographic masks and a prism on its 18 positions. Each of the two spectrometer wheels is equipped with two disks on both sides of a central torque motor, one of them carries 6 gratings, the other a dichroic/mirror arrangement. The optical positions are defined by a ratchet mechanism. No closed loop control is required; therefore the long time average heat dissipation is negligible. A new ratchet mechanism had to be developed to satisfy a 120° increment of only three positions for the spectrometer wheels.
Extensive cold and warm tests were performed on the development models of the filter and spectrometer wheels at
MPIA. These results stimulated numerous improvements in the mechanical and thermal design which are now to be
implemented in the qualification and flight models developed jointly with Carl Zeiss. Synergies are expected from a
similar development of the NIRSPEC wheels, in which MPIA and Carl Zeiss are involved.
LINC-NIRVANA is an infrared camera that will work in Fizeau interferometric way at the Large Binocular Telescope (LBT). The two beams that will be combined in the camera are corrected by an MCAO system, aiming to cancel the turbulence in a scientific field of view of 2 arcminutes. The MCAO wavefront sensors will be two for each arm, with the task to sense the atmosphere at two different altitudes (the ground one and a second height variable between a few kilometers and a maximum of 15 kilometers). The first wavefront sensor, namely the Ground layer Wavefront sensor (GWS), will drive the secondary adaptive mirror of LBT, while the second wavefront sensor, namely the Mid High layer Wavefront Sensor (MHWS) will drive a commercial deformable mirror which will also have the possibility to be conjugated to the same altitude of the correspondent wavefront sensor. The entire system is of course duplicated for the two telescopes, and is based on the Multiple Field of View (MFoV) Layer Oriented (LO) technique, having thus different FoV to select the suitable references for the two wavefront sensor: the GWS will use the light of an annular field of view from 2 to 6 arcminutes, while the MHWS will use the central 2 arcminutes part of the FoV. After LINC-NIRVANA has accomplished the final design review, we describe the MFoV wavefront sensing system together with its current status.
LINC-NIRVANA is the IR Fizeau interferometric imager of the Large Binocular Telescope (LBT) in Arizona.
Here we describe in particular the design, realization and preliminary tests of the so-called Patrol Camera. It
can image (in the range 600-900 nm) the same 2 arcmin FoV seen by the Medium- High-Wavefront Sensor
(MHWS), adequately sampled to provide the MHWS star enlargers with the positions of the FoV stars with
an accuracy of 0.1 arcsec. To this aim a diffraction-limited performance is not required, while a distortion free
focal plane is needed to provide a suitable astrometric output. Two identical systems will be realized, one for
each single arm, which corresponds to each single telescope. We give here the details concerning the optical
and mechanical design, as well as the CCD and the control system. The interfaces with LINC-NIRVANA are
also presented both in terms of matching the carbon fiber optical bench and developing of suitable software
procedures. Since the major components have been already gathered, the laboratory tests and the integration
are currently in progress.
The Mid-High Wavefront Sensors (MHWS) are components of the adaptive optics system of LINC-NIRVANA, the Fizeau interferometer that will be mounted at the LBT. These sensors, one for each telescope arm, will measure the atmospheric turbulence in the high altitude layers, using up to 8 reference stars in a 2 arcmin Field of View, and they will be coupled with two Ground Layer WFSs that will measure the lower part of the atmospheric turbulence using up to 12 stars over an annular Field of View from 2 to 6 arcmin in diameter. We will describe the opto-mechanical layout of the MHWS and the Assembly, Integration and Test (AIT) phase of the first sensor in the laboratory of the Bologna Observatory.
The Adaptive Optics System of the Galileo Telescope (AdOpt@TNG) is the only adaptive optics system mounted on a telescope which uses a pyramid wavefront snesor and it has already shown on sky its potentiality. Recently AdOpt@TNG has undergone deep changes at the level of its higher orders control system. The CCD and the Real Time Computer (RTC) have been substituted as a whole. Instead of the VME based RTC, due to its frequent breakdowns, a dual pentium processor PC with Real-Time-Linux has been chosen. The WFS CCD, that feeds the images to the RTC, was changed to an off-the-shelf camera system from SciMeasure with an EEV39 80x80 pixels as detector. While the APD based Tip/Tilt loop has shown the quality on the sky at the TNG site and the ability of TNG to take advantage of this quality, up to the diffraction limit, the High-Order system has been fully re-developed and the performance of the closed loop is under evaluation to offer the system with the best performance to the astronomical community.
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