The use of flexures to achieve fibre positioner motion is being actively investigated by several institutes, for example at the UK Astronomy Technology Centre (UKATC) and Leibniz-Institute for Astrophysics Potsdam [1]. One challenge when designing with flexures is the large number of degrees of freedom available which makes it difficult or impossible to optimise their motion by hand.
In this paper we demonstrate two approaches for optimising flexure geometry to follow arbitrary focal surface curvature and to orient the optical fibre with arbitrary tilt. These approaches are: analytical using MATLAB models and FEA based using Ansys. The approaches are complementary allowing the designer to efficiently explore the parameter space and then do precise optimisation of the flexure geometry. We demonstrate the applicability both to the UKATC’s preferred design for WST, and to flexure-based fibre positioner designs generally. We also present a sensitivity analysis relating small changes in design parameters to changes in fibre tip motion. Finally we briefly present the UKATC's preferred geometry for the WST fibre positioner.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450 nm to 2450 nm with resolving powers from 3500 to 18000 and spatial sampling from 60 mas to 4 mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews. HARMONI is a work-horse instrument that provides efficient, spatially resolved spectroscopy of extended objects or crowded fields of view. The gigantic leap in sensitivity and spatial resolution that HARMONI at the ELT will enable promises to transform the landscape in observational astrophysics in the coming decade. The project has undergone some key changes to the leadership and management structure over the last two years. We present the salient elements of the project restructuring, and modifications to the technical specifications. The instrument design is very mature in the lead up to the final design review. In this paper, we provide an overview of the instrument's capabilities, details of recent technical changes during the red flag period, and an update of sensitivities.
We describe the instrument’s design and architecture, emphasizing its unique features. The design is driven by requirements on resolving power, slit area, spectral coverage and stability. The instrument can operate in seeinglimited or SCAO modes, with options for sky and/or calibration measurements. In SCAO mode, it can use a small Integral Field Unit (IFU) with different spaxel scales. The light from the telescope reaches the Front-End on the Nasmyth platform, which has four insertable modules: two seeing-limited arms, one SCAO arm and one IFU arm. They are connected by fibres or fibre bundles to the Spectrographs in different locations: the Nasmyth Platform and the Coud´e room. The wavelength splitting depends on the fibre transparency. The subsystems are placed at different distances from the telescope. In Phase-B-one, we performed analyses to define the best trade-off for the budgets and architecture. We extended the spectrographs toward the goal ranges as much as possible. ANDES is complex, but its sophisticated and modular design will enable next-generation astronomy research.
MOSAIC is the Multi-Object Spectrograph (MOS) for the 39m Extremely Large Telescope (ELT) of the European Southern Observatory (ESO), with unique capabilities in terms of multiplex, wavelength coverage and spectral resolution. It is a versatile multi-object spectrograph working in both the Visible and NIR domains, designed to cover the largest possible area (∼40 arcmin2) on the focal plane, and optimized to achieve the best possible signal-to-noise ratio on the faintest sources, from stars in our Galaxy to galaxies at the epoch of the reionization. In this paper we describe the main characteristics of the instrument, including its expected performance in the different observing modes. The status of the project will be briefly presented, together with the positioning of the instrument in the landscape of the ELT instrumentation. We also review the main expected scientific contributions of MOSAIC, focusing on the synergies between this instrument and other major ground-based and space facilities.
The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 μm with the goal of extending it to 0.35-2.4 μm with the addition of an U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allows ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states.
MOONS (Multi-Object Optical and Near-infrared Spectrograph) is a third-generation visible and near-infrared spectrograph for the ESO Very Large Telescope, currently nearing the end of the assembly phase. The three channel spectrograph is fed via a fibre positioning module (FPM) which configures the location of 1001 fibres. The robotic fibre positioning units (FPUs) have been jointly developed by the UK Astronomy Technology Centre (UKATC) and MPS Microsystems (MPS) and provide a high-performance multiplexed focal plane with excellent transmission characteristics. An overview of the as-built mechanisms and supporting infrastructure is presented, with details on the extensive calibration process carried out. The integration process to date will be described, including a discussion of key lessons learned.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 40mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews. The Focal Plane Relay Sub-System (FPRS) relays the ELT's Nasymth A2 focal plane to the HARMONI IFS focal plane. The FPRS maintains a -15°C environment to reduce additional thermal noise and contains two Ø600 mm x 20 mm windows in a double-glazing arrangement at the entrance. The external window surface temperature will be below the ambient telescope temperature due to insulation limitations and could lead to condensation forming reducing optical throughput and increased scatter, in particular in the IR-bands. We present the design and testing of a window flushing solution utilizing air knife technology
HARMONI is the first light, adaptive optics assisted, integral field spectrograph for the European Southern Observatory’s Extremely Large Telescope (ELT). A work-horse instrument, it provides the ELT’s diffraction limited spectroscopic capability across the near-infrared wavelength range. HARMONI will exploit the ELT’s unique combination of exquisite spatial resolution and enormous collecting area, enabling transformational science. The design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument’s capabilities from a user perspective, and provide a summary of the instrument’s design. We also include recent changes to the project, both technical and programmatic, that have resulted from red-flag actions. Finally, we outline some of the simulated HARMONI observations currently being analyzed.
The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs (UBV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 µm with the goal of extending it to 0.35-2.4 µm with the addition of a K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Its modularity will ensure that ANDES can be placed entirely on the ELT Nasmyth platform, if enough mass and volume is available, or partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of more than 200 scientists and engineers which represent the majority of the scientific and technical expertise in the field among ESO member states.
The Natural Guide Star Sensors (NGSS) system of HARMONI provides wavefront and image stabilisation sensing for each of the observing modes of the instrument. The Focal Plane Relay System (FPRS) relays and redirects the telescope beam from the ELT Prefocal Station (PFS) to the NGSS and spectrograph. To limit thermal background and to ensure the required stability, the sensors and optics are contained in a dry gas environment stabilized at -15 degrees Celsius. Achieving this cooled, dry environment requires an insulated enclosure, cooling system and dry air flushing system. These measures present certain novel challenges; the design solutions are described here.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for final design review (FDR). The Natural Guide Star Sensors (NGSS) system of HARMONI provides wavefront and image stabilization sensing for each of the four observing modes of the instrument, LTAO, SCAO, HCAO, and NOAO. It consists of five subsystems, three of which provide wavefront sensing (LOWFS, SCAOS and HCM), the remaining two (ESE and ISB) providing thermal and mechanical functions. To limit thermal background and to ensure the required stability, the sensors operate in a cold, thermally stabilized, dry gas environment. This paper presents the overall design of the system with emphasis on system analysis, assembly and test, and maintenance.
MOONS (Multi-Object Optical and Near-infrared Spectrograph) is a third-generation visible and near-infrared spectrograph for the ESO Very Large Telescope currently under construction. The instrument’s spectroscopic capabilities are multiplexed via a fibre positioning module (FPM) which configures the location of 1001 fibres. The fibre positioning units (FPUs) have been jointly developed by the UK Astronomy Technology Centre (UKATC) and MPS Microsystems (MPS) to optimise instrument efficiency by providing excellent transmission and an open-loop positioning strategy, allowing a tightly packed focal plane to be rapidly reconfigured. The mechanism geometry enables all positions in the focal plane to be observed in conjunction with a companion sky fibre at close separation. A description of the as manufactured design and production process of the FPUs is presented, along with a discussion of the performance proven to date, including achievement of the critical pupil alignment and positional repeatability requirements. An overview of the custom testing rig built to automate the characterisation and calibration process is also presented.
HARMONI is the adaptive optics assisted, near-infrared and visible light integral field spectrograph for the Extremely Large Telescope (ELT). A first light instrument, it provides the work-horse spectroscopic capability for the ELT. As the project approaches its Final Design Review milestone, the design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument’s capabilities from a user perspective, provide a summary of the instrument’s design, including plans for operations and calibrations, and provide a brief glimpse of the predicted performance for a specific observing scenario. The paper also provides some details of the consortium composition and its evolution since the project commenced in 2015.
The construction of the next generation of 40 m-class astronomical telescopes poses an enormous challenge for the design of their instruments and the manufacture of their optics. Optical elements typically increase in both size and number, placing ever more demands on the system manufacturing and alignment tolerances. This challenge can be met by using the wider design space offered by freeform optics, by for instance allowing highly aspherical surfaces. Optical designs incorporating freeform optics can achieve a better performance with fewer components. This also leads to savings in volume and mass and, potentially, cost.
This paper describes the characterization of the FAME system (freeform active mirror experiment). The system consists of a thin hydroformed face sheet that is produced to be close to the required surface shape, a highly controllable active array that provides support and the ability to set local curvature of the optical surface and the actuator layout with control electronics that drives the active array.
A detailed characterisation of the fully-assembled freeform mirror was carried out with the physical and optical properties determined by coordinate measurements (CMM), laser scanning, spherometry and Fizeau interferometry. The numerical model of the mirror was refined to match the as-built features and to predict the performance more accurately.
Each of the 18 actuators was tested individually and the results allow the generation of look-up tables providing the force on the mirror for each actuator setting. The actuators were modelled with finite element analysis and compared to the detailed measurements to develop a closed-loop system simulation. After assembling the actuators in an array, the mirror surface was measured again using interferometry. The influence functions and Eigen-modes were also determined by interferometry and compared to the FEA results.
Large aperture telescope technology (LATT) is a design study for a differential lidar (DIAL) system; the main investigation being into suitable methods, technologies and materials for a 4-metre diameter active mirror that can be stowed to fit into a typical launch vehicle (e.g. ROKOT launcher with ∼ 2.1-metre diameter cargo) and can self-deploy – in terms of both leaving the space vehicle and that the mirrors unfold and self-align to the correct optical form within the tolerances specified. The primary mirror requirements are: main wavelength of 935.5 nm, RMS corrected wavefront error of λ/6, optical surface roughness better than 5 nm, areal density of less than 16 kg/m2 and 1-2 mirror shape corrections per orbit. The primary mirror consists of 7 segments - a central hexagonal mirror and 6 square mirror petals which unfold to form the 4-meter diameter aperture. The focus of the UK LATT consortium for this European Space Agency (ESA) funded project is on using lightweighted aluminium or carbon-fibre-composite materials for the mirror substrate in preference to more traditional materials such as glass and ceramics; these materials have a high strength and stiffness to weight ratio, significantly reducing risk of damage due to launch forces and subsequent deployment in orbit.
We present an overview of the design, which includes suitable actuators for wavefront correction, petal deployment mechanisms and lightweight mirror technologies. Preliminary testing results from manufactured lightweight mirror samples will also be summarised.
The Multi-Object Optical and Near-infrared Spectrograph (MOONS) will cover the Very Large Telescope's (VLT) field of view with 1000 fibres. The fibres will be mounted on fibre positioning units (FPU) implemented as two-DOF robot arms to ensure a homogeneous coverage of the 500 square arcmin field of view. To accurately and fast determine the position of the 1000 fibres a metrology system has been designed. This paper presents the hardware and software design and performance of the metrology system. The metrology system is based on the analysis of images taken by a circular array of 12 cameras located close to the VLTs derotator ring around the Nasmyth focus. The system includes 24 individually adjustable lamps. The fibre positions are measured through dedicated metrology targets mounted on top of the FPUs and fiducial markers connected to the FPU support plate which are imaged at the same time. A flexible pipeline based on VLT standards is used to process the images. The position accuracy was determined to ~5 μm in the central region of the images. Including the outer regions the overall positioning accuracy is ~25 μm. The MOONS metrology system is fully set up with a working prototype. The results in parts of the images are already excellent. By using upcoming hardware and improving the calibration it is expected to fulfil the accuracy requirement over the complete field of view for all metrology cameras.
The Multi-Object Optical and Near-Infrared Spectrograph (MOONS) will exploit the full 500 square arcmin field of view offered by the Nasmyth focus of the Very Large Telescope and will be equipped with two identical triple arm cryogenic spectrographs covering the wavelength range 0.64μm-1.8μm, with a multiplex capability of over 1000 fibres. This can be configured to produce spectra for chosen targets and have close proximity sky subtraction if required. The system will have both a medium resolution (R~4000-6000) mode and a high resolution (R~20000) mode. The fibre positioning units are used to position each fibre independently in order to pick off each sub field of 1.0” within a circular patrol area of ~85” on sky (50mm physical diameter). The nominal physical separation between FPUs is 25mm allowing a 100% overlap in coverage between adjacent units. The design of the fibre positioning units allows parallel and rapid reconfiguration between observations. The kinematic geometry is such that pupil alignment is maintained over the patrol area. This paper presents the design of the Fibre Positioning Units at the preliminary design review and the results of verification testing of the advanced prototypes.
HARMONI is the E-ELT’s first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 × 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the E-ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers (R ~3500, 7500 and 20000) and instantaneous wavelength coverage spanning the 0.5 – 2.4 μm wavelength range of the instrument. In autumn 2015, the HARMONI project started the Preliminary Design Phase, following signature of the contract to design, build, test and commission the instrument, signed between the European Southern Observatory and the UK Science and Technology Facilities Council. Crucially, the contract also includes the preliminary design of the HARMONI Laser Tomographic Adaptive Optics system. The instrument’s technical specifications were finalized in the period leading up to contract signature. In this paper, we report on the first activity carried out during preliminary design, defining the baseline architecture for the system, and the trade-off studies leading up to the choice of baseline.
FAME is a four-year project and part of the OPTICON/FP7 program that is aimed at providing a breakthrough component for future compact, wide field, high resolution imagers or spectrographs, based on both Freeform technology, and the flexibility and versatility of active systems.
Due to the opening of a new parameter space in optical design, Freeform Optics are a revolution in imaging systems for a broad range of applications from high tech cameras to astronomy, via earth observation systems, drones and defense. Freeform mirrors are defined by a non-rotational symmetry of the surface shape, and the fact that the surface shape cannot be simply described by conicoids extensions, or off-axis conicoids. An extreme freeform surface is a significantly challenging optical surface, especially for UV/VIS/NIR diffraction limited instruments.
The aim of the FAME effort is to use an extreme freeform mirror with standard optics in order to propose an integrated system solution for use in future instruments. The work done so far concentrated on identification of compact, fast, widefield optical designs working in the visible, with diffraction limited performance; optimization of the number of required actuators and their layout; the design of an active array to manipulate the face sheet, as well as the actuator design.
In this paper we present the status of the demonstrator development, with focus on the different building blocks: an extreme freeform thin face sheet, the active array, a highly controllable thermal actuator array, and the metrology and control system.
The UK ATC has developed a novel thermal actuator design as part of an OPTICON project focusing on the development of a Freeform Active Mirror Element (FAME). The actuator uses the well understood concept of thermal expansion to generate the required force and displacement. As heat is applied to the actuator material it expands linearly. A resistance temperature device (RTD) is embedded in the centre of the actuator and is used both as a heater and a sensor. The RTD temperature is controlled electronically by injecting a varying amount of current into the device whilst measuring the voltage across it. Temperature control of the RTD has been achieved to within 0.01°C.
A 3D printed version of the actuator is currently being used at the ATC to deform a mirror but it has several advantages that may make it suitable to other applications. The actuator is cheap to produce whilst obtaining a high accuracy and repeatability. The actuator design would be suitable for applications requiring large numbers of actuators with high precision.
The Multi-Object Optical and Near-infrared Spectrograph (MOONS) is a new fiber-fed spectrograph for the VLT. MOONS will exploit the full 500 square arcmin field of view offered by the Nasmyth focus of VLT and will be equipped with two dual-arm spectrographs covering the wavelength range 0.8 µm-1.8 μm, with a possible extension down to 0.5 μm. Each double-arm spectrograph will produce spectra for 250 targets simultaneously, each with its own dedicated sky fiber for optimal sky subtraction. The system will have both a medium resolution (R 3000 - 5000) mode and a high resolution (R 20000) mode to allow detailed dynamical and chemical studies. To ensure the accurate positioning of the 500 fiber pairs over the focal plane that has 880 mm in diameter, a metrology system has been designed to provide position measurements within 7.5 μm considering that the final positioning accuracy of each fiber with respect to the target object must be less than 15 μm. The metrology system is composed by a circular array of 12 cameras located at VLT’s de-rotator ring around the Nasmyth focus. The paper presents the design of the metrology system and discusses the proposed methodology to align multiple the views of the focal plane array.
HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrometer, providing the E-ELT's core
spectroscopic capability, over a range of resolving powers from R (≡λ/Δλ)~500 to R~20000. The instrument provides simultaneous spectra of ~32000 spaxels at visible and near-IR wavelengths, arranged in a √2:1 aspect ratio contiguous field. HARMONI is conceived as a workhorse instrument, addressing many of the E-ELT’s key science cases, and will
exploit the E-ELT's scientific potential in its early years, starting at first light. HARMONI provides a range of spatial
pixel (spaxel) scales and spectral resolving powers, which permit the user to optimally configure the instrument for a
wide range of science programs; from ultra-sensitive to diffraction limited, spatially resolved, physical (via morphology),
chemical (via abundances and line ratios) and kinematic (via line-of-sight velocities) studies of astrophysical sources.
Recently, the HARMONI design has undergone substantial changes due to significant modifications to the interface with
the telescope and the architecture of the E-ELT Nasmyth platform. We present an overview of the capabilities of
HARMONI, and of its design from a functional and performance viewpoint.
MOONS will exploit the full 500 square arcmin field of view offered by the Nasmyth focus of the Very Large Telescope
and will be equipped with two identical triple arm cryogenic spectrographs covering the wavelength range 0.8 - 1.8 μm,
with a multiplex capability of approximately 1000 fibres. Each triple arm spectrograph will produce spectra for half of
the targets simultaneously. The system will have both a medium resolution (R~4000-6000) mode and a high resolution
(R~20000) mode.
The fibres are used to pick off each sub field of 1.05 arcseconds and are used to transport the light from the instrument
focal plane to the two spectrographs. Each fibre has a microlens to focus the beam into the fibre at a relative fast focal
ratio of F/3.65 to reduce the Focal Ratio Degradation (FRD).
This paper presents the overall design of the fibre system and describes the specific developments required to optimise
its performance. The design of the fibre input optics, the choice of the fibre connector, and the layout of the slit end are
described. The results of preliminary tests to measure the effect of twisting on the FRD performance of prototype fibres
are also discussed.
MOONS is a new Multi-Object Optical and Near-infrared Spectrograph selected by ESO as a third generation
instrument for the Very Large Telescope (VLT). The grasp of the large collecting area offered by the VLT (8.2m
diameter), combined with the large multiplex and wavelength coverage (optical to near-IR: 0.8μm - 1.8μm) of MOONS
will provide the European astronomical community with a powerful, unique instrument able to pioneer a wide range of
Galactic, Extragalactic and Cosmological studies and provide crucial follow-up for major facilities such as Gaia,
VISTA, Euclid and LSST. MOONS has the observational power needed to unveil galaxy formation and evolution over
the entire history of the Universe, from stars in our Milky Way, through the redshift desert, and up to the epoch of very
first galaxies and re-ionization of the Universe at redshift z>8-9, just few million years after the Big Bang. On a
timescale of 5 years of observations, MOONS will provide high quality spectra for >3M stars in our Galaxy and the
local group, and for 1-2M galaxies at z>1 (SDSS-like survey), promising to revolutionise our understanding of the
Universe.
The baseline design consists of ~1000 fibers deployable over a field of view of ~500 square arcmin, the largest patrol
field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8μm-1.8μm and two resolution
modes: medium resolution and high resolution. In the medium resolution mode (R~4,000-6,000) the entire wavelength
range 0.8μm-1.8μm is observed simultaneously, while the high resolution mode covers simultaneously three selected
spectral regions: one around the CaII triplet (at R~8,000) to measure radial velocities, and two regions at R~20,000 one
in the J-band and one in the H-band, for detailed measurements of chemical abundances.
KMOS is a multi-object near-infrared integral field spectrograph built by a consortium of UK and German institutes for
the ESO Paranal Observatory. We report on the on-sky performance verification of KMOS measured during three
commissioning runs on the ESO VLT in 2012/13 and some of the early science results.
KMOS is a multi-object near-infrared integral field spectrograph being built by a consortium of UK and German
institutes. We report on the final integration and test phases of KMOS, and its performance verification, prior to
commissioning on the ESO VLT later this year.
MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large
Telescope (VLT), selected by ESO for a Phase A study. The baseline design consists of ~1000 fibers deployable over a
field of view of ~500 square arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total
wavelength coverage is 0.8μm-1.8μm and two resolution modes: medium resolution and high resolution. In the medium
resolution mode (R~4,000-6,000) the entire wavelength range 0.8μm-1.8μm is observed simultaneously, while the high
resolution mode covers simultaneously three selected spectral regions: one around the CaII triplet (at R~8,000) to
measure radial velocities, and two regions at R~20,000 one in the J-band and one in the H-band, for detailed
measurements of chemical abundances.
The grasp of the 8.2m Very Large Telescope (VLT) combined with the large multiplex and wavelength coverage of
MOONS – extending into the near-IR – will provide the observational power necessary to study galaxy formation and
evolution over the entire history of the Universe, from our Milky Way, through the redshift desert and up to the epoch
of re-ionization at z<8-9. At the same time, the high spectral resolution mode will allow astronomers to study chemical
abundances of stars in our Galaxy, in particular in the highly obscured regions of the Bulge, and provide the necessary
follow-up of the Gaia mission. Such characteristics and versatility make MOONS the long-awaited workhorse near-IR
MOS for the VLT, which will perfectly complement optical spectroscopy performed by FLAMES and VIMOS.
HARMONI is a visible and near-IR integral field spectrograph, providing the E-ELT's spectroscopic capability at first
light. It obtains simultaneous spectra of 32000 spaxels, at a range of resolving powers from R~4000 to R~20000,
covering the wavelength range from 0.47 to 2.45 μm. The 256 × 128 spaxel field of view has four different plate scales,
with the coarsest scale (40 mas) providing a 5″ × 10″ FoV, while the finest scale is a factor of 10 finer (4mas).
We describe the opto-mechanical design of HARMONI, prior to the start of preliminary design, including the main subsystems
- namely the image de-rotator, the scale-changing optics, the splitting and slicing optics, and the spectrographs.
We also present the secondary guiding system, the pupil imaging optics, the field and pupil stops, the natural guide star
wavefront sensor, and the calibration unit.
A multiple pick off mirror positioning sub-system has been developed as a solution for the deployment of mirrors within
multi-object instrumentation such as the EAGLE instrument in the European Extremely Large Telescope (E-ELT). The
positioning sub-system is a two wheeled differential steered friction drive robot with a footprint of approximately 20 x
20 mm. Controlled by RF communications there are two versions of the robot that exist. One is powered by a single cell
lithium ion battery and the other utilises a power floor system. The robots use two brushless DC motors with 125:1
planetary gear heads for positioning in the coarse drive stages. A unique power floor allows the robots to be positioned at
any location in any orientation on the focal plane. The design, linear repeatability tests, metrology and power continuity
of the robot will be evaluated and presented in this paper. To gather photons from the objects of interest it is important to
position POMs within a sphere of confusion of less than 10 μm, with an angular alignment better than 1 mrad. The
robots potential of meeting these requirements will be described through the open-loop repeatability tests conducted with
a Faro laser beam tracker. Tests have involved sending the robot step commands and automatically taking continuous
measurements every three seconds. Currently the robot is capable of repeatedly travelling 233 mm within 0.307 mm at 5
mm/s. An analysis of the power floors reliability through the continuous monitoring of the voltage across the tracks with
a Pico logger will also be presented.
HARMONI is an integral field spectrograph working at visible and near-infrared wavelengths, over a range of
spatial scales from ground layer corrected to fully diffraction-limited. The instrument has been chosen to be
part of the first-light complement at the European Extremely Large Telescope (E-ELT).
This paper describes the engineering technology development being undertaken at the UKATC and Oxford to
support E-ELT HARMONI instrument in its pre-phase-B stage. This includes the description of technology
demonstrators for a tracking optical de-rotator to be located within the instrument vacuum vessel, a cryogenic
shutter and a compact thermally compensating lens mount system. In addition the material testing facilities
available at the UKATC are described which will enable the measurement of material and bolted joint thermal
conductivities to 4K and friction/wear properties of material combinations to 20K. This work is undertaken to
improve the instrument performance and reduce technical, cost and schedule risk.
We have been developing a series of novel technological solutions to address the challenges posed by the adaptive optic
requirements for extremely large telescopes. Our deformable mirror surface material, a compliant from of silicon
carbide, offers a Young's Modulus comparable to glass but with greater, non-catastrophic, resistance to fracture. In
combination with the extraordinary new material we have been working on a new low power actuator with a deflection
capability of tens of microns. We have considered the systems requirements for our deformable mirror and developed
both a coating technology and a unique use of hydroxide catalysis bonding.
The start of the new generation of giant telescopes opens a good opportunity to re-assess the cryogenic cooling of the
instruments and detectors. An analysis has been carried out comparing three different technologies: Mechanical cryocoolers,
helium forced flow and open liquid nitrogen cooling. The most different aspects from the running cost to the
reliability and technology readiness have been compared in order to establish a fair ranking. The first part of the paper
will present in detail the result of this analysis.
Based on this study and the various experiences collected over more than 25 years and a large number of cryogenic
instruments, a strategy is elaborated for the cryogenic cooling of the E-ELT (European Extremely Large Telescope)
instrument suite.
The challenge consists in providing various cryogenic temperatures (from 10 K to 240 K) at various locations. This
should be done in the most efficient way with the minimum of disturbances (low vibration, low thermal dissipation...). A
discussion presents the advantages of the selected solution.
The complexity and size of instruments for next generation telescopes demands innovative approaches to existing
problems. Within this framework, we present MAPS; a Micro Autonomous Positioning System for mirror deployment in
an E-ELT instrument such as EAGLE. The micro-robots have a 25mmx25mm footprint and utilise RF communications
and small rechargeable batteries to be completely wireless. Coarse positioning and fine alignment is achieved through
the use of miniature gear motors and gearheads. Positional information is determined externally and corrective motions
relayed to the robots. This paper reports on the challenges which such a system presents, current developments, and areas
of expected future research.
Over preceding conferences, the design and implementation of the SCUBA-2 (Sub-millimeter Common-User
Bolometric Array 2) instrument hardware has been described in detail. SCUBA-2 has been installed on the James Clerk
Maxwell Telescope (JCMT) for over two years and its hardware has been successfully commissioned. This paper
describes the culmination of this process and compares the optical/mechanical design and test expectations of the
instrument hardware against the performance achieved in the field.
KMOS is a near-infrared multi-object integral-field spectrometer which is one of a suite of second-generation
instruments under construction for the VLT. The instrument is being built by a consortium of UK and German
institutes working in partnership with ESO and is now in the manufacture, integration and test phase. In this paper
we present an overview of recent progress with the design and build of KMOS and present the first results from the
subsystem test and integration.
We present a conceptual design for a Precision Radial Velocity Spectrograph (PRVS) for the Gemini telescope. PRVS is
a fibre fed high resolving power (R~70,000 at 2.5 pixel sampling) cryogenic echelle spectrograph operating in the near
infrared (0.95 - 1.8 microns) and is designed to provide 1 m/s radial velocity measurements. We identify the various
error sources to overcome in order to the required stability. We have constructed models simulating likely candidates
and demonstrated the ability to recover exoplanetary RV signals in the infrared. PRVS should achieve a total RV error of
around 1 m/s on a typical M6V star. We use these results as an input to a simulated 5-year survey of nearby M stars.
Based on a scaling of optical results, such a survey has the sensitivity to detect several terrestrial mass planets in the
habitable zone around nearby stars. PRVS will thus test theoretical planet formation models, which predict an abundance
of terrestrial-mass planets around low-mass stars.We have conducted limited experiments with a brass-board instrument
on the Sun in the infrared to explore real-world issues achieving better than 10 m/s precision in single 10 s exposures and
better than 5 m/s when integrated across a minute of observing.
The performance requirements for the next generation of ground-based instruments for optical and infrared astronomy
on current telescopes and future ELTs are generating extreme requirements for stability, for instance to carry out precise
radial velocity measurements, imaging and spectroscopy with high contrast, and diffraction-limited performance at a
level of tens of milliarcsecond. As it is not always possible to make use of a gravity-invariant focal station, flexure must
be accommodated while still minimising thermal loads for cryogenic instruments. Variable thermal loads are another
source of dimensional changes. High stability will require the minimising of the effects of vibration sources, either from
the telescope systems or mechanical coolers. All this must be done while maintaining mass budgets, an especial
challenge for large, wide-field, multi-object spectrographs.
This paper describes the opto-mechanical design of a large instrument for sub-mm, SCUBA-2, to be commissioned at JCMT. The scientific requirements, specially the large fov and the constraints of the telescope mechanical structure, lead to a complex optical design using freeform aluminium mirrors . The mechanical design is also challenging with large modules to be mounted and aligned in the telescope as well as the cryogenic instrument containing the mirrors, the filters, the dichroics and the detector modules. The cryogenic isostatic mounting, the structural and thermal designs are presented. This includes details of the fabrication of the structure and design of a shutter mechanism for operation at 4K. The results of the first AIV cool-down are also presented.
SCUBA-2 is an innovative 10,000 pixel submillimeter camera due to be delivered to the James Clerk Maxwell Telescope in late 2006. The camera is expected to revolutionize submillimeter astronomy in terms of the ability to carry out wide-field surveys to unprecedented depths addressing key questions relating to the origins of galaxies, stars and planets. This paper presents an update on the project with particular emphasis on the laboratory commissioning of the instrument. The assembly and integration will be described as well as the measured thermal performance of the instrument. A summary of the performance results will be presented from the TES bolometer arrays, which come complete with in-focal plane SQUID amplifiers and multiplexed readouts, and are cooled to 100mK by a liquid cryogen-free dilution refrigerator. Considerable emphasis has also been placed on the operating modes of the instrument and the "common-user" aspect of the user interface and data reduction pipeline. These areas will also be described in the paper.
The SCUBA-2 instrument is a new wide-field imager under development for the James Clerk Maxwell Telescope on Mauna Kea in Hawaii and due to be operational in 2006. The instrument has two separate focal planes and is designed to observe simultaneously at wavelengths of 450 and 850μm. The instrument cryostat will weigh around 2500kg and has a volume of approximately 2.4x1.8x2.0m. The two detector arrays are operated at ~100mK and are surrounded by a cold enclosure at ~1K. Both the arrays and cold enclosure are cooled by a novel, liquid cryogen-free dilution refrigerator. To reduce the thermal background on the arrays to a minimum the main optics structure, weighing in excess of 450kg, must be cooled to less than 15K. A pair of low vibration pulse tube coolers are used to cool this structure and a radiation shield at ~60K. This paper describes the cryo-mechanical design of SCUBA-2 and discusses some of the issues and techniques needed to both cool the instrument within a reasonable timescale, and operate it in the required temperature regime
An update on the design status of the UKIRT Wide Field Camera (WFCAM) is presented. WFCAM is a wide field infrared camera for the UK Infrared Telescope, designed to produce large scale infrared surveys. The complete system consists of a new IR camera with integral autoguider and a new tip/tilt secondary mirror unit. WFCAM is being designed and built by a team at the UK Astronomy Technology Centre in Edinburgh, supported by the Joint Astronomy Centre in Hawaii. The camera uses a novel quasi-Schmidt camera type design, with the camera mounted above the UKIRT primary mirror. The optical system operates over 0.7 - 2.4 μm and has a large corrected field of view of 0.9° diameter. The focal plane is sparsely populated with 4 2K x 2K Rockwell HAWAII-2 MCT array detectors, giving a pixel scale of 0.4 arcsec/pixel. A separate autoguider CCD is integrated into the focal plane unit. Parallel detector controllers are used, one for each of the four IR arrays and a fifth for the autoguider CCD.
The UKATC has recently delivered and commissioned the Michelle mid-IR spectrograph on UKIRT. This instrument has a variety of precision vacuum-cryogenic mechanisms that utilize technology developed over a number of years at the UKATC in instruments such as IRCAM, CGS4, SCUBA, GMOS and UIST. In these applications it is critical that the mechanisms operate reliably and with a high degree of precision. In most cases the mechanisms support optical elements that must be rigidly held in place when the instrument is tilted during observations on the telescope. This paper describes the level of performance achieved with the Michelle mechanisms and the critical elements of their design.
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