MAVIS is the world’s first facility-grade visible MCAO instrument, currently under development for the VLT. The AO system will feed an imager and an integral field spectrograph, with 50% sky coverage at the Galactic pole. MAVIS has unique angular resolution and sensitivity at visible wavelengths, and is highly complementary to both JWST and ELTs. We describe both instruments in detail and the broad range of science cases enabled by them. The imager will be diffraction-limited in V, with 7.36 mas per pixel covering a 30” FOV. A set of at least 7 broad-band and 15 narrow-band filters will provide imaging from u to z. The spectrograph uses an advanced image slicer with a selectable spatial sampling of 25 or 50 mas to provide integral field spectroscopy over a FOV of 2.5”x3.6”, or 5”x7.2”. The spectrograph has two identical arms each covering half the FOV. Four interchangeable grisms allow spectroscopy with R=5,000 to R=15,000, from 380-950 nm.
The proposed MAVIS instrument for the VLT UT4 delivers a 30" x 30" MCAO-corrected field for 370-950nm. It includes an integral-field spectroscopic mode, whereby a subsection of the field is delivered to an image slicer and spectrograph, with either 25mas or 50mas spatial sampling, and R<4000 and R<10000 modes in either the red or the blue. Three designs are being considered for the image slicer, two with all-reflective optics, and the other, presented here, derived from the existing WiFeS spectrograph and including arrays of small lenses. A spectrograph design is also presented, challenging because of the need to be close to diffraction-limited across the entire wavelength range, while maintaining high throughput, in all 4 modes and over the entire 9cm x 9cm detector.
The Hector instrument was installed at the Anglo-Australian Telescope in December 2021 and received the first light. It consists of three major subsystems, namely, the positioner, spectrograph and optical cable. Spector is the new spectrograph with an average spectral resolution of R=4500 designed for hexabundles, the fiber integral field units. Details of the integration and testing of the spectrograph optics are presented here. Each assembled subsystem was interferometrically checked for wavefront quality. The system spectral performance was fine tuned using a test fiber slit to achieve required resolution across the field of view. The absolute transmittance of the spectrograph bulk optics was measured in both blue and red channels.
MAVIS is a future imaging spectrograph for the VLT in which the spectrograph is fed by an IFU. Imager and IFU are fed by Multi-Conjugate Adaptive Optics for the wavelength range 370 nm to 930 nm. The spectrograph will deliver a spectral resolution of more than 4000. The IFU field has a choice of 2 spaxel sizes. It is 9 arsec2 with 25 mas spaxels and 36 arsec2 with 50 mas. The design follows the proven concept of Advanced Image Slicer (AIS) as for Gemini NIFS and GNIRS, VLT MUSE and KMOS, JWST NIRSpec, and many others. In the present design, the field is first split in 2 and each subfield is imaged on a slicer mirror array made of long thin mirrors that slice the field into 50 images and send them in different directions to be reimaged side by side on the slit by another mirror array. Additional optics on the slit reimage the pupil at the right place in the spectrograph. Three different options are under study for the slit optics. One is a mirror array of considerably lower cost than the standard design in an AIS. At 25 mas, the spaxels are near the diffraction limit of the longest wavelength. This present challenges not present for seeing limited IFUs as focal ratio degradation due to diffraction by the slices. Another challenge comes from the short minimum wavelength. It is difficult to manufacture efficient reflection coatings for the whole wavelength range. Transmissive fore-optics were then also studied. The field splitter which sends half the field to each of the 2 arms was integrated into the fore-optics. This removes 2 air-glass surfaces from each arm.
The MCAO Assisted Visible Imager and Spectrograph (MAVIS) is a facility-grade visible MCAO instrument, currently under development for the Adaptive Optics Facility at the VLT. The adaptive optics system will feed both an imager and an integral field spectrograph, with unprecedented sky coverage of 50% at the Galactic Pole. The imager will deliver diffraction-limited image quality in the V band, cover a 30" x 30" field of view, with imaging from U to z bands. The conceptual design for the spectrograph has a selectable field-of-view of 2.5" x 3.6", or 5" x 7.2", with a spatial sampling of 25 or 50 mas respectively. It will deliver a spectral resolving power of R=5,000 to R=15,000, covering a wavelength range from 380 - 950 nm. The combined angular resolution and sensitivity of MAVIS fill a unique parameter space at optical wavelengths, that is highly complementary to that of future next-generation facilities like JWST and ELTs, optimised for infrared wavelengths. MAVIS will facilitate a broad range of science, including monitoring solar system bodies in support of space missions; resolving protoplanetary- and accretion-disk mechanisms around stars; combining radial velocities and proper motions to detect intermediate-mass black holes; characterising resolved stellar populations in galaxies beyond the local group; resolving galaxies spectrally and spatially on parsec scales out to 50 Mpc; tracing the role of star clusters across cosmic time; and characterising the first globular clusters in formation via gravitational lensing. We describe the science cases and the concept designs for the imager and spectrograph.
"We present initial results from the Multi-conjugate Adaptive-optics Visible Imager-Spectrograph Image Simulator (MAVISIM) to explore the astrometric capabilities of the next generation instrument MAVIS. A core scientific and operational requirement of MAVIS will be to achieve highly accurate differential astrometry, with accuracies on the order that of the extremely large telescopes. To better understand the impact of known and anticipated astrometric error terms, we have created an initial astrometric budget which we present here to motivate the creation of MAVISIM. In this first version of MAVISIM we include three major astrometric error sources; point spread function (PSF) field variability due to high order aberrations, PSF degradation and field variability due to tip-tilt residual error, and field distortions due to non-common path aberrations in the AO module. An overview of MAVISIM is provided along with initial results from a study using MAVISIM to simulate an image of a Milky Way-like globular cluster. Astrometric accuracies are extracted using PSF-fitting photometry with encouraging results that suggest MAVIS will deliver accuracies of 150µas down to faint magnitudes."
The Macquarie University campus observatory has recently undergone a significant upgrade, with a new fully- automated 0.6 m telescope and on-site facilities including an instrumentation laboratory. Here we report on the design, assembly, and first on-sky tests of a new high-resolution echelle spectrograph for the observatory. This spectrograph will be a key resource at our campus observatory, providing high fidelity measurements that will enable future research, in particular Master and PhD theses that require stellar spectroscopy or radial velocity measurements. The instrument will also form a cornerstone of the laboratory components of the undergraduate astronomy degree, and together with the new 0.6 m telescope, a key tool for project-based learning at the campus observatory. The instrument has been developed with radial velocity precision as the driving metric, and with future work on the environmental stabilisation it is expected to reach a radial velocity precision of 3 m s−1, enabling the observation of a wide range of exoplanets.
KEYWORDS: Visible radiation, James Webb Space Telescope, Observatories, Adaptive optics, Large telescopes, Spectrographs, Spatial resolution, Hubble Space Telescope, Telescopes
A consortium of several Australian and European institutes – together with the European Southern Observatory (ESO) – has initiated the design of MAVIS, a Multi-Conjugate Adaptive Optics (MCAO) system for the ground- based 8-m Very Large Telescope (VLT). MAVIS (MCAO-assisted Visible Imager and Spectrograph) will deliver visible images and integral field spectrograph data with 2-3x better angular resolution than the Hubble Space Telescope, making it a powerful complement at visible wavelengths to future facilities like the space-based James Webb Space Telescope and the 30 to 40m-class ground-based telescopes currently under construction, which are all targeting science at near-infrared wavelengths. MAVIS successfully passed its Phase A in May 2020. We present the motivations, requirements, principal design choices, conceptual design, expected performance and an overview of the exciting science enabled by MAVIS.
Based on the success of the SAMI integral field spectrograph (IFS) instrument on the Anglo-Australian Telescope (AAT) the capacity for large IFS nearby galaxy surveys on the AAT is being substantially expanded with a new instrument called Hector. The high filling-fraction imaging fibre bundles ‘hexabundles’ of the type used on SAMI, are being enlarged to cover up to 30-arcsec diameter. The aim is to reach two effective radii on most galaxies, where the galaxy rotation curve flattens and >75% of the specific angular momentum of disk galaxies is accounted for. Driven by the key science case, Hector will have a 1.3A spectral resolution, enabling high-order stellar kinematics to be measured on a larger fraction of galaxies than with any other IFS instrument. Hector will be on sky in 2019.
The first module of Hector, Hector-I, will have 21 hexabundles and >42 sky fibres to observe 20 galaxies and a calibration star simultaneously. It consists of new blue and red-arm spectrographs that have been designed at the Australian Astronomical Observatory (AAO; now called AAO-Macquarie), coupled to the new hexabundles and robotic positioner from AAO-USydney (formerly the Sydney Astrophotonics Instrumentation Laboratory, SAIL) at Sydney University. A novel robotic positioning concept will compensate for varying telecentricity over the 2-degree-field of the AAT to recoup the 20% loss in light at the edge of the field. Hector-I will survey 15,000 galaxies. Additional modules in the future would result in 30,000 galaxies.
Hector will take integral field spectroscopy on galaxies with z<0.15 in the 4MOST WAVES-North and WAVES-South∗ regions. The WAVES data, which will come later, will give the environment metrics neces- sary to relate how local and global environments influence galaxy growth through gas accretion, star formation and spins measured with Hector. The WALLABY ASKAP† survey will trace HI gas across the Hector fields, which in combination with Hector will give a complete view of gas accretion and star formation.
GHOST is a high resolution spectrograph system currently being built for the Gemini South Observatory in Chile. In the Cassegrain unit, the observational targets are acquired on integral field units and guided during science exposures, feeding the fiber cable to the temperature-stabilized echelle spectrograph. The Cassegrain unit is mounted on the Gemini telescope, and consists of a main structural plate, the two object positioners and ballast frame. The image from each of the two science beams passes through a field lens and a mini-atmospheric dispersion corrector and is then captured by the integral field unit. The positioner moves each corrector-integral field unit assembly across the focal surface of the telescope. The main structural plate provides the interface for the positioner and ballast frame to the telescope structure. In this paper we describe the final design and assembly of the GHOST Cassegrain unit and report on the outcome of on-sky testing at the telescope in Chile.
The Gemini High-resolution Optical SpecTrograph (GHOST) is a fiber fed spectrograph primarily designed for high efficiency and broad wavelength coverage (363 -1000nm), with an anticipated commissioning early in 2018. The primary scientific goal of the Precision Radial Velocity (PRV) mode will be follow-up of relatively faint (R>12) transiting exoplanet targets, especially from the TESS mission. In the PRV mode, the 1.2 arcsec diameter stellar image will be split 19 ways, combined in a single slit with a simultaneous Th/Xe reference source, dispersed at a resolving power of 80,000 and imaged onto two detectors. The spectrograph will be thermally stabilized in the Gemini pier laboratory, and modal noise will be reduced below other sources through the use of a fiber agitator. Unlike other precision high resolution spectrographs, GHOST will not be pressure controlled (although pressure will be monitored precisely), and there will be no double scrambler or shaped (e.g. octagonal) fibers. Instead, GHOST will have to rely on simultaneous two-color imaging of the slit and the simultaneous Th/Xe fiber to correct for variable fiber illumination and focal-ratio degradation. This configuration presents unique challenges in estimating a PRV error budget.
Hector[1,2,3] will be the new massively-multiplexed integral field spectroscopy (IFS) instrument for the Anglo-Australian Telescope (AAT) in Australia and the next main dark-time instrument for the observatory. Based on the success of the SAMI instrument, which is undertaking a 3400-galaxy survey, the integral field unit (IFU) imaging fibre bundle (hexabundle) technology under-pinning SAMI is being improved to a new innovative design for Hector. The distribution of hexabundle angular sizes is matched to the galaxy survey properties in order to image 90% of galaxies out to 2 effective radii. 50-100 of these IFU imaging bundles will be positioned by ‘starbug’ robots across a new 3-degree field corrector top end to be purpose-built for the AAT. Many thousand fibres will then be fed into new replicable spectrographs. Fundamentally new science will be achieved compared to existing instruments due to Hector's wider field of view (3 degrees), high positioning efficiency using starbugs, higher spectroscopic resolution (R=3000-5500 from 3727-7761Å, with a possible redder extension later) and large IFUs (up to 30 arcsec diameter with 61-217 fibre cores). A 100,000 galaxy IFS survey with Hector will decrypt how the accretion and merger history and large-scale environment made every galaxy different in its morphology and star formation history. The high resolution, particularly in the blue, will make Hector the only instrument to be able to measure higher-order kinematics for galaxies down to much lower velocity dispersion than in current large IFS galaxy surveys, opening up a wealth of new nearby galaxy science.
The Gemini High-Resolution Optical SpecTrograph (GHOST) is the newest instrument being developed for the Gemini telescopes, in a collaboration between the Australian Astronomical Observatory (AAO), the NRC - Herzberg in Canada and the Australian National University (ANU). We describe the process of design optimisation that utilizes the unique strengths of the new partner, NRC - Herzberg, the design and need for the slit viewing camera system, and we describe a simplification for the lenslet-based slit reformatting. Finally, we out- line the updated project plan, and describe the unique scientific role this instrument will have in an international context, from exoplanets through to the distant Universe.
The Gemini North (GN) AO system, Altair, has been routinely operating in LGS mode since 2007. Due to the initial
optical design, the NGS field-of-view (FoV) is limited to a radius ~ 25" which limits the potential science. To improve
this, we have tested the AO/LGS operation using a peripheral wavefront sensor (PWFS) whose patrol field is ~ 4'-7'
from the target. This expanded NGS FoV permits greater sky coverage but with decreased resolution, FWHM ~ 0.1" -
0.2" making this mode very suitable for non-imaging spectrographic and integral field unit observations. We present the
hardware and software upgrades to PWFS and Altair as well as the software necessary for making this observing mode a
routine and integral part of GN operations. Characterization and performance of this new operation mode, known as
LGS+P1, are presented.
We present observations of early-type galaxies with laser guide star adaptive optics (LGS AO) obtained at Gemini North
telescope using the NIFS integral field unit (IFU). We employ an innovative technique where the focus compensation
due to the changing distance to the sodium layer is made 'open loop', allowing the extended galaxy nucleus to be used
only for tip-tilt correction. The purpose of these observations is to determine high spatial resolution stellar kinematics
within the nuclei of these galaxies to determine the masses of the super-massive black holes. The resulting data have
spatial resolution of 0.2" FWHM or better. This is sufficient to positively constrain the presence of the central black hole
in even low-mass early-type galaxies, suggesting that larger samples of such objects could be observed with this
technique in the future. The open-loop focus correction technique is a supported queue-observing mode at Gemini,
significantly extending the sky coverage in particular for faint, extended guide sources. We also provide preliminary
results from tests combining tip/tilt correction from the Gemini peripheral guider with on-axis LGS. The current test
system demonstrates feasibility of this mode, providing about a factor 2-3 improvement over natural seeing. With
planned upgrades to the peripheral wave-front sensor, we hope to provide close to 100% sky coverage with low Strehl
corrections, or 'improved seeing', significantly increasing flux concentration for deep field and extended object studies.
We present up-to-date performance characteristics for natural guide star (NGS) operation of the ALTAIR adaptive optics
system at the Gemini N. 8m telescope. These results are obtained from a nightly performance monitoring campaign
where we obtain a consistent set of point spread functions (PSFs) over a broad range of observing conditions. These
results are compared with system modelling and circular buffer information from the Altair adaptive optics (AO) system.
The latter show residual tip-tilt errors with a median rms ~ 18.5 mas. We also present preliminary results from a new
operational mode of the laser guide star (LGS) AO which will eventually yield all-sky access with image FWHM ~ 0.1"
- 0.2".
The Multi-Unit Spectroscopic Explorer (MUSE) is an integral-field spectrograph for the VLT for the next decade. Using
an innovative field-splitting and slicing design, combined with an assembly of 24 spectrographs, MUSE will provide
some 90,000 spectra in one exposure, which cover a simultaneous spectral range from 465 to 930nm. The design and
manufacture of the Calibration Unit, the alignment tests of the Spectrograph and Detector sub-systems, and the
development of the Data Reduction Software for MUSE are work-packages under the responsibility of the AIP, who is a
partner in a European-wide consortium of 6 institutes and ESO, that is led by the Centre de Recherche Astronomique de
Lyon. MUSE will be operated and therefore has to be calibrated in a variety of modes, which include seeing-limited and
AO-assisted operations, providing a wide and narrow-field-of-view. MUSE aims to obtain unprecedented ultra-deep 3D-spectroscopic
exposures, involving integration times of the order of 80 hours at the VLT. To achieve the corresponding
science goals, instrumental stability, accurate calibration and adequate data reduction tools are needed. The paper
describes the status at PDR of the AIP related work-packages, in particular with respect to the spatial, spectral, image
quality, and geometrical calibration and related data reduction aspects.
The GLAS (Ground-layer Laser Adaptive-optics System) project is to construct a common-user Rayleigh laser beacon that will work in conjunction with the existing NAOMI adaptive optics system, instruments (near IR imager INGRID, optical integral field spectrograph OASIS, coronagraph OSCA) and infrastructure at the 4.2-m William Herschel Telescope (WHT) on La Palma. The laser guide star system will increase sky coverage available to high-order adaptive optics from ~1% to approaching 100% and will be optimized for scientific exploitation of the OASIS integral-field spectrograph at optical wavelengths. Additionally GLAS will be used in on-sky experiments for the application of laser beacons to ELTs. This paper describes the full range of engineering of the project ranging through the laser launch system, wavefront sensors, computer control, mechanisms, diagnostics, CCD detectors and the safety system. GLAS is a fully funded project, with final design completed and all equipment ordered, including the laser. Integration has started on the WHT and first light is expected summer 2006.
The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 0.465-0.93 μm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 0.6-0.93 μm wavelength range. Although the MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, environment of young stellar objects, super massive black holes and active nuclei in nearby galaxies or massive spectroscopic surveys of stellar fields in the Milky Way and nearby galaxies.
The Adaptive Optics Facility is a project to convert one VLT-UT into a specialized Adaptive Telescope. The present
secondary mirror (M2) will be replaced by a new M2-Unit hosting a 1170 actuators deformable mirror. The 3 focal
stations will be equipped with instruments adapted to the new capability of this UT. Two instruments are in
development for the 2 Nasmyth foci: Hawk-I with its AO module GRAAL allowing a Ground Layer Adaptive Optics
correction and MUSE with GALACSI for GLAO correction and Laser Tomography Adaptive Optics correction. A
future instrument still needs to be defined for the Cassegrain focus. Several guide stars are required for the type of
adaptive corrections needed and a four Laser Guide Star facility (4LGSF) is being developed in the scope of the AO
Facility. Convex mirrors like the VLT M2 represent a major challenge for testing and a substantial effort is dedicated to
this. ASSIST, is a test bench that will allow testing of the Deformable Secondary Mirror and both instruments with
simulated turbulence. This article describes the Adaptive Optics facility systems composing associated with it.
The Multi Unit spectroscopic Explorer (MUSE) is a second generation VLT panoramic integral-field spectrograph operating in the visible wavelength range. MUSE has a field of 1 x 1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by a ground layer adaptive optics system using four laser guide stars. The simultaneous spectral range is 0.465-0.93 μm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5 x 7.5 arcse2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to get diffraction limited data-cube in the 0.6-1 μm wavelength range. Although MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, young stellar objects environment, supermassive black holes and active nuclei in nearby galaxies or massive spectroscopic survey of stellar fields.
By incorporating spatial coverage with the spectral dimension,
integral-field spectroscopy is uniquely suited for exploiting the
capabilities of adaptive optics (AO) systems. OASIS is a lenslet-based integral-field spectrograph designed to perform high-resolution
observations on AO-corrected sources, operating at visible
wavelengths. This instrument was commissioned at the William Herschel
Telescope, La Palma, in July 2003 to work with the ING's AO system,
NAOMI. Here we present an overview of the capabilities of the
OASIS+NAOMI system, and show results obtained using this technique. The science presented here is a small preview of what will be possible for a large number of objects when the GLAS laser guide system is operational.
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