HARMONI is a visible and near-infrared integral field spectrograph equipped with two complementary adaptive optics systems, fully integrated within the instrument. A Single Conjugate AO (SCAO) system offers high performance for a limited sky coverage and a Laser Tomographic AO (LTAO) system provides AO correction with a very high sky-coverage. While the deformable mirror performing real-time correction of the atmospheric disturbances is located within the telescope itself, the instrument contains a suite of state-of-the-art and innovative wavefront sensor systems. Laser guide star sensors (LGSS) are located at the entrance of the instrument and fed by a dichroic beam splitter, while the various natural guide star sensors for LTAO and SCAO are located close to the science focal plane. We present opto-mechanical architecture and design at PDR level for these wavefront sensor systems.
HARMONI is a first-light visible and near-IR integral field spectrograph of ESO’s Extremely Large Telescope (ELT) which will sit on top of Cerro Armazones, Chile. A Single Conjugate Adaptive Optics (SCAO) subsystem will provide diffraction-limited spectro-images in a Nyquist-sampled 0.61 x 0.86 arcsec field of view, with a R=3000-20000 spectral resolution. Inside the instrument, a High Contrast Module (HCM) could give HARMONI the ability to spectrally characterize young giant exoplanets (and disks) with flux ratio down to 10−6 as close as 100-200mas from their star. This would be achieved with an apodized pupil coronagraph to attenuate the diffracted light of the star and limit the dynamic range on the detector, and an internal ZELDA wavefront sensor to calibrate non-common path aberrations, assuming that the surface quality of the relay optics of HARMONI satisfy specific requirements. This communication presents (a) the system analysis that was conducted to converge towards these requirement, and the proposed HCM design, (b) an end-to-end simulation tool that has been built to produce realistic datacubes of hour-long observations, and (c) the estimated performance of the HCM, which has been derived by applying differential imaging techniques on the simulated data.
Harmoni is the 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 ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers from R 3500 to R 20000 and instantaneous wavelength coverage spanning the 0.47 - 2.45 μm wavelength range of the instrument. The consortium consists of several institutes in Europe under leadership of Oxford University. Harmoni is starting its Final Design Phase after a Preliminary Design Phase in November, 2017. The CRAL has the responsibility of the Integral Field Unit design linking the Preoptics to the 4 Spectrographs. It is composed of a field splitter associated with a relay system and an image slicer that create from a rectangular Field of View a very long (540mm) output slit for each spectrograph. In this paper, the preliminary design and performances of Harmoni Image Slicer will be presented including image quality, pupil distortion and slit geometry. It has been designed by CRAL for Harmoni PDR in November, 2017. Special emphases will be put on straylight analysis and slice diffraction. The optimisation of the manufacturing and slit geometry will also be reported.
HARMONI is a visible and near-infrared (0.5 to 2.45 μm) integral field spectrograph, providing the E-ELT's core spectroscopic capability, over a range of resolving powers from R (λ/Δλ) ~ 3500 to ~18000. The instrument provides simultaneous spectra of ∼32000 spaxels arranged in a sqrt(2):1 aspect ratio contiguous field. The pre-optics take light entering the science cryostat (from the telescope or calibration system), reformatting and conditioning to be suitable for input for the rest of the instrument. This involves many functions, mainly relaying the light from the telescope focal plane to the integral field unit (IFU) focal plane via a set of interchangeable scale changing optics. The pre-optics also provides components including a focal plane mask wheel, cold pupil masks, spectral order sorting filters, a fast shutter, and a pupil imaging capability to check telescope/instrument pupil alignment. In this paper, we present the optical design of the HARMONI pre-optics at Preliminary Design Review and, in particular, we detail the differences with the previous design and the difficulties salved to the Preliminary Design Review.
HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrograph, providing the ELT's core spectroscopic capability at first light. A pre-optics subsystem provides four selectable spatial pixel scales, in addition to other beam conditioning functions such as shutter and pupil masks. For the validation of the mechanisms in charge of these functions (fast shutter and the plane mask wheel) we have planned some prototypes to test the design solutions.
The focal plane mask wheel sits in the input focus of the cryostat. It provides 16 user-selectable positions for masks (28x40 mm) used in observation. The key driver for this mechanism is the high repeatability (±2.5 μm) required, equivalent to ~1mas in the input focal plane. The IAC has previously designed, manufactured, tested and put in operation cryogenic wheels with high repeatability; however, the challenge of obtaining a wheel with such repeatability requires testing new concepts of detent positioning systems.
The shutter allows for exposures shorter than the minimum read time of the near-IR detectors and is needed for any CCD observations with the visible cameras. A dual shutter design is needed to achieve the necessary open/close times (<20 ms), but this also provides some redundancy and a graceful failure mode for this critical device. To mitigate risks on the proper behaviour of a fast cryogenics shutter a prototype based on a simple concept has been manufactured. We present the design and results for the performed cryogenic tests of a mask wheel and a shutter prototypes that we have developed.
HARMONI is the first light integral field spectrograph for the ELT. It includes a core 'science instrument' -- the IFS -- supported by a range of other systems, in particular adaptive optics sensors for SCAO and LTAO. The latter was, for many years, treated as an entirely separate instrument with the ELT observatory architecture. A better understanding of the technical challenges, together with a changing political and funding environment, led to merger of the two projects in 2014. The project now rates over 400FTE with a commensurately large hardware budget.
The IFS part of the instrument, at least in function, remains largerly unchanged since 2009 when the consortium completed a Phase A study as part of the (then 42m) E-ELT instrument studies. The structure of the consortium was essentially fixed then, and many firm (and soft) contractual agreements and understandings limit the flexibility to match work to product. Over the years however, as the ELT project has evolved, the design and scope of HARMONI has changed and expanded. This has brought new partners into the consortium, changed the design concept of the instrument, introduced new interfaces, and updated requirements. To further complicate matters, as of PDR (late 2017) the final scope of the project is still open due to funding uncertainties.
All of these factors have made the development of a system architecture particularly challenging. The architecture of 2009 - whilst ultimately linked to the structure of the consortium - is no longer fit for the technical purpose. A revised system architecture, and the resulting product breakdown structure, have had to be carefully adapted to satisfy a wide range of constraints. It must be solid enough to allow the project to progress clearly, but flexible enough to deal with what changes may lie ahead.
We have applied systems engineering processes to develop and architecture which is clean and robust, whilst including some inevitable compromise driven by overall project considerations. The paper will describe the processes we have followed, how the architecture has evolved, and how we have dealt with constraints and compromises forced by the existing consortium structure. We will present the baseline architecture for HARMONI, and explain how this maps onto other areas of the project and the overall instrument development process. This is an example of system architecting in the real world of moving targets and immovable obstructions.
HARMONI is a first-light visible and near-IR integral field spectrograph of ESO’s Extremely Large Telescope (ELT) which will sit on top of Cerro Armazones, Chile. A Single Conjugate Adaptive Optics (SCAO) sub-system will provide diffraction-limited spectral images in a Nyquist-sampled 0.61 × 0.86 arcsec field of view, with a R=3000-20000 spectral resolution. Inside the instrument, a High Contrast Module (HCM) will add an essential high-contrast imaging capability for HARMONI to spectrally characterize young giant exoplanets and disks with flux ratio down to 1e-6 at 0.1-0.2” from their star. The HCM uses an apodized pupil coronagraph to lower the intensity of the diffracted starlight and limit the dynamic range on the detector, and an internal wavefront sensor to calibrate non-common path aberrations. This communication first summarizes the basic technical requirements of the HCM, then describes its optical and mechanical designs, and presents expected performance in terms of achievable contrast, image quality and throughput. Elements of the development and test program are also given.
Twinkle is a space mission designed for visible and near-IR spectroscopic observations of extrasolar planets. Twinkle’s highly stable instrument will allow the photometric and spectroscopic observation of a wide range of planetary classes around different types of stars, with a focus on bright sources close to the ecliptic. The planets will be observed through transit and eclipse photometry and spectroscopy, as well as phase curves, eclipse mapping and multiple narrow-band time-series. The targets observed by Twinkle will be composed of known exoplanets mainly discovered by existing and upcoming ground surveys in our galaxy (e.g. WASP, HATNet, NGTS and radial velocity surveys) and will also feature new discoveries by space observatories (K2, GAIA, Cheops, TESS). Twinkle is a small satellite with a payload designed to perform high-quality astrophysical observations while adapting to the design of an existing Low Earth Orbit commercial satellite platform. The SSTL-300 bus, to be launched into a low- Earth sun-synchronous polar orbit by 2019, will carry a half-meter class telescope with two instruments (visible and near-IR spectrographs - between 0.4 and 4.5μm - with resolving power R~300 at the lower end of the wavelength scale) using mostly flight proven spacecraft systems designed by Surrey Satellite Technology Ltd and a combination of high TRL instrumentation and a few lower TRL elements built by a consortium of UK institutes. The Twinkle design will enable the observation of the chemical composition and weather of at least 100 exoplanets in the Milky Way, including super-Earths (rocky planets 1-10 times the mass of Earth), Neptunes, sub-Neptunes and gas giants like Jupiter. It will also allow the follow-up photometric observations of 1000+ exoplanets in the visible and infrared, as well as observations of Solar system objects, bright stars and disks.
HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrograph over a range of resolving powers from R~3000 to R~20000. We will present in this paper, the different concepts of the HARMONI Integral Field Unit that makes the link between HARMONI Preoptics and the 4 Spectrographs. It is composed of a field splitter/relay system and an image slicer that creates from a rectangular Field of View a very long (532mm) pseudo-slit for each spectrograph. HARMONI is also considering a separate visible spectrograph and we present a possible image slicer for this option.
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.
Proc. SPIE. 9908, Ground-based and Airborne Instrumentation for Astronomy VI
KEYWORDS: Sensors, Control systems, Computer programming, Photonic integrated circuits, Computer aided design, Commercial off the shelf technology, Cryogenics, Camera shutters, Prototyping, Temperature metrology
HARMONI is an integral field spectrograph working at visible and near-infrared wavelengths. The instrument will be part of the first-light complement at the E-ELT. The IAC is in charge of several work packages and the design of two important components is ongoing: A 'Cryogenic Pupil Mask Rotator' based on a direct drive brushless motor, and a 'Cryogenic Fast Shutter' based on voice coil. One of the main goals of these developments is the use of COTS (Commercial-Off-The-Shelf) parts since their use will reduce costs and short the schedule. Nevertheless, the application of COTS parts in cryo-vacuum is often very difficult and represents a technological challenge.
ESA has been funding the industry in Europe to bring the technologies together to manufacture high performance infrared detectors from near infrared (NIR) to very long wavelength infrared (VLWIR) detectors. The UK Astronomy Technology Centre (UKATC) has undertaken the tasks of test and characterizing the new detectors being manufactured by Leonardo, UK (Selex ES Ltd). Initial test results from these programs were presented at previous SPIE meetings in 2012 and 2014. The work since has much progressed to test and characterize the Large Format NIR, SWIR and LW and VLWIR detectors. This paper will present the custom built test facilities for evaluation of large format (currently 1280x1024, 15μm pixel format) near infrared detectors for astronomy applications, the characterization of 1Kx1K shortwave infrared detectors (cut off at 2.5μm on a 2Kx2K ROIC) for satellite based earth observation programs, long wavelength (8 to 11.5μm) and very long wavelength (10 to 14.5μm) 288 x 384 pixel infrared arrays for cosmos applications. Also being evaluated in at the UKATC is a SAPHIRA APD array (mark 5) for photon sensing and high speed AO applications. Custom test facilities have been setup at the UKATC and are being routinely used to test and characterize these detectors under conditions representative of the applications. The paper will discuss the requirements placed on testing in each of these programs along with the associated challenges to evaluate the performance of these detectors. The paper will also include some of the latest test results from the characterization programs, where appropriate.
HARMONI is a visible and near-infrared integral field spectrograph designed to be a first-light instrument on the European extremely large telescope. It will use both single-conjugate and laser tomographic adaptive optics to fully exploit high-performance and sky coverage. Using a fast AO modelling toolbox, we simulate anisoplanatism effects on the point spread function of the single-conjugate adaptive optics of HARMONI. We investigate the degradation of the correction performance with respect to the off-axis distance in terms of Strehl ratio and ensquared energy. In addition, we analyse what impact the natural guide source magnitude, AO sampling frequency and number of sub-apertures have on performance.
We show, in addition to the expected PSF degradation with the field direction, that the PSF retains a coherent core even at large off-axis distances. We demonstrated the large performance improvement of fine tuning the sampling frequency for dimer natural guide stars and an improvement of approx. 50% in SR can be reached above the nominal case. We show that using a smaller AO system with only 20x20 sub-apertures it is possible to further increase performance and maintain equivalent performance even for large off-axis angles.
HARMONI is a visible and NIR integral field spectrograph, providing the E-ELT’s core spectroscopic capability at first light. HARMONI will work at the diffraction limit of the E-ELT, thanks to a Classical and a Laser Tomographic AO system. In this paper, we present the system choices that have been made for these SCAO and LTAO modules. In particular, we describe the strategy developed for the different Wave-Front Sensors: pyramid for SCAO, the LGSWFS concept, the NGSWFS path, and the truth sensor capabilities. We present first potential implementations. And we asses the first system performance.
The Exoplanet Characterisation Observatory (EChO) mission was one of the proposed candidates for the European Space Agency’s third medium mission within the Cosmic Vision Framework. EChO was designed to observe the spectra from transiting exoplanets in the 0.55-11 micron band with a goal of covering from 0.4 to 16 microns. The mission and its associated scientific instrument has now undergone a rigorous technical evaluation phase and we report here on the outcome of that study phase, update the design status and review the expected performance of the integrated payload and satellite.
EChO (Exoplanet atmospheres Characterization Observatory), a proposal for exoplanets exploration space mission, is considered the next step for planetary atmospheres characterization. It would be a dedicated observatory to uncover a large selected sample of planets spanning a wide range of masses (from gas giants to super-Earths) and orbital temperatures (from hot to habitable). All targets move around stars of spectral types F, G, K, and M. EChO would provide an unprecedented view of the atmospheres of planets in the solar neighbourhood. The consortium formed by various institutions of different countries proposed as ESA M3 an integrated spectrometer payload for EChO covering the wavelength interval 0.4 to 16 µm. This instrument is subdivided into 4 channels: a visible channel, which includes a fine guidance system (FGS) and a VIS spectrometer, a near infrared channel (SWiR), a middle infrared channel (MWiR), and a long wave infrared module (LWiR). In addition, it contains a common set of optics spectrally dividing the wavelength coverage and injecting the combined light of parent stars and their exoplanets into the different channels. The proposed payload meets all of the key performance requirements detailed in the ESA call for proposals as well as all scientific goals. EChO payload is based on different spectrometers covering the spectral range mentioned above. Among them, SWiR spectrometer would work from 2.45 microns to 5.45 microns. In this paper, the optical and mechanical designs of the SWiR channel instrument are reported on.
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.
The spectrograph sub-system is responsible for dispersing the light from the slicer with the required spectral resolving
power and imaging the spectra on to a detector. Each image slicer creates a single exit slit feeding a single spectrograph
unit containing visible (VIS) and infrared (IR) cameras. The four HARMONI slicers in total create four exit slits, feeding
four spectrograph units comprising of collimators, dispersers, and cameras. The focal plane of each camera contains a
mosaic of two 4Kx4K detectors, leading to 8K pixels along the length of the slit. The HARMONI wavelength range
(0.43 μm to 2.45 μm) splits into a visible and a near-infrared wavelength range with a transition wavelength at 0.8 μm. The optical design of HARMONI up to the dispersers is fully reflective and therefore the pre-optics and IFU subsystems,
as well the spectrograph collimator, can be used for both the visible and near-infrared wavelength range. Only
the dispersers and the spectrograph cameras are different for the visible and near infrared spectral ranges. To not
duplicate sub-systems unnecessarily the wavelength split in the spectrograph is realised by inserting a dichroic in the
collimated beam before the disperser to either direct the light towards the visible disperser and camera, or let it pass
toward the near-infrared disperser and camera. In contrast to the Phase A study all of HARMONI spectrograph unit will
have both visible and near infrared disperser and cameras.
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 instrument control electronics to be developed at IAC. The large size of the
HARMONI instrument, its cryogenic operation, and the fact that it must operate with enhanced reliability
is a challenge from the point of view of the control electronics design. The present paper describes a
design proposal based on the current instrument requirements and intended to be fully compliant with the
ESO E-ELT standards, as well as with the European EMC and safety standards. The modularity of the
design and the use of COTS standard hardware will benefit the project in several aspects, as reduced
costs, shorter schedule by the use of commercially available components, and improved quality by the use
of well proven solutions.
HARMONI is a visible and near-infrared (0.47μm to 2.5μm) integral field spectrometer providing the E-ELT's core
spectroscopic capability. It will provide ~32000 simultaneous spectra of a rectangular field of view at four foreseen
different spatial sample (spaxel) scales. The HARMONI fore-optics re-formats the native telescope plate scale to suitable
values for the downstream instrument optics. This telecentric adaptation includes anamorphic magnification of the plate
scale to optimize the performance of the IFU, which contains the image slicer, and their four spectrographs. In addition,
it provides an image of the telescope pupil to assemble a cold stop shared among all the scales allowing efficient
suppression of the thermal background. A pupil imaging unit also re-images the pupil cold stop onto the image slicer to
check the relative alignment between the E-ELT and HARMONI pupils. The scale changer will also host the filter wheel
with the long-pass filters to select the wavelength range. The main reasoning specifying the importance of the
HARMONI fore-optics and its current optical and mechanical design is described in this contribution.
The UKATC has undertaken to test and evaluate new infrared detectors being developed at Selex ES Ltd, Southampton in the UK for astronomy and space applications. Current programmes include: the evaluation of large format (1280×1024), near-infrared detectors for astronomy, the characterisation of shortwave infrared detectors (up to 2.5μm) for satellite-based earth observation, long wavelength (8 to 11μm) and very long wavelength (10 to 14.5μm cut-off) devices for cosmos applications. Future programmes include the evaluation of large format, avalanche photodiode arrays for photon-level sensing and high speed applications. Custom test facilities are being setup in order to drive and characterise the detectors at the ATC under conditions representative of the applications. In this paper the test facilities will be described along with the associated challenges to evaluate the performance of these detectors. The paper also includes an overview of the Selex ES detectors, including the ROICs and the MOVPE HgCdTe arrays, and will present the latest results from the characterisation program.
In order to improve the signal-to-noise ratio of HARMONI (E-ELT first light visible and near-infrared integral field VIR
spectrometer), a pupil mask has been identified to be included at the fore-optics to limit the background radiation coming
into the spectrographs. This mask should rotate synchronously with the telescope pupil during observations, taking into
account the combined effects of the telescope tracking and the de-rotation of the FOV. The implementation of the pupil
mask functionality will require complex movements with high precision at cryogenic temperatures which implies an
important technological challenge.
This paper details a set of experiments completed to gain knowledge and experience in order to accomplish the design
and control of cryogenic mechanisms reaching this type of pupil motion. The conceptual design of the whole mechanism
started from the feedback acquired from those experiments is also described in the following sections.
HARMONI is an integral field spectrograph working in the visible and near-infrared (0.47 to 2.45 μm) and will provide
the E-ELT’s core spectroscopic capability, starting at first light. To minimise the thermal background it will be a
cryogenic instrument with the optomechanics inside the cryostat having an operating temperature of 130K. We have
designed three different thermally compensating lens mounts and have started analysing their performance by measuring
the position of a glass blank relative to the mount to look for any displacement and tilt as it cooled down to operating
temperature. The suitability of a commercial iris shutter for use in HARMONI is also assessed and found to work down
to 120K, though further work is needed to prove it is reliable enough to be included in HARMONI, including an
accelerated lifetime test.
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
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.
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.
The Exoplanet Characterisation Observatory (EChO) is a space mission dedicated to undertaking spectroscopy of
transiting exoplanets over the widest wavelength range possible. It is based around a highly stable space platform with a
1.2 m class telescope. The mission is currently being studied by ESA in the context of a medium class mission within
the Cosmic Vision programme for launch post 2020. The payload suite is required to provide simultaneous coverage
from the visible to the mid-infrared and must be highly stable and effectively operate as a single instrument. In this
paper we describe the integrated spectrometer payload design for EChO which will cover the 0.4 to 16 micron
wavelength band. The instrumentation is subdivided into 5 channels (Visible/Near Infrared, Short Wave InfraRed, 2 x Mid Wave InfraRed; Long Wave InfraRed) with a common set of optics spectrally dividing the input beam via dichroics.
We discuss the significant design issues for the payload and the detailed technical trade-offs that we are undertaking to
produce a payload for EChO that can be built within the mission and programme constraints and yet which will meet the
exacting scientific performance required to undertake transit spectroscopy.
EChO, a space mission for exoplanets exploration, is considered the next step for planetary atmospheres
characterization. It will be a dedicated observatory to uncover a large selected sample of planets spanning a
wide range of masses (from gas giants to super-Earths) and orbital temperatures (from hot to habitable). All
targets move around stars of spectral types F, G, K, and M. EChO will provide an unprecedented view of the
atmospheres of planets in the solar neighbourhood.
The consortium formed by various institutions of different countries is proposing an integrated
spectrometer payload for EChO covering the wavelength interval 0.4 to 16 µm. This instrument is subdivided
into 4 channels: a visible channel, which includes a fine guidance system (FGS) and a VIS spectrometer, a
near infrared channel (SWiR), a middle infrared channel (MWiR), and a long wave infrared module (LWiR).
In addition, it contains a common set of optics spectrally dividing the wavelength coverage and injecting the
combined light of parent stars and their exoplanets into the different channels. The proposed payload meets all
of the key performance requirements detailed in the ESA call for proposals as well as all scientific goals.
EChO payload will be based on different spectrometers covering the spectral range mentioned above.
Among them, SWiR spectrometer will work from 2.45 microns to 5.45 microns. In this paper, the optical and
mechanical designs of the SWiR channel instrument, including the evolution of the different trades followed
and the current identification of critical points, are reported on.
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)
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.
EAGLE is an instrument under consideration for the European Extremely Large Telescope (E-ELT). EAGLE will be
installed at the Gravity Invariant Focal Station of the E-ELT. The baseline design consists of 20 IFUs deployable over a
patrol field of ~40 arcmin2. Each IFU has an individual field of view of ~ 1.65" x 1.65". While EAGLE can operate with
the Adaptive Optics correction delivered by the telescope, its full and unrivaled scientific power will be reached with the
added value of its embedded Multi-Object Adaptive Optics System (MOAO). EAGLE will be a unique and efficient
facility for spatially-resolved, spectroscopic surveys of high-redshift galaxies and resolved stellar populations. We detail
the three main science drivers that have been used to specify the top level science requirements. We then present the
baseline design of the instrument at the end of Phase A, and in particular its Adaptive Optics System. We show that the
instrument has a readiness level that allows us to proceed directly into phase B, and we indicate how the instrument
development is planned.
EAGLE is a wide FoV (5 arcmin diameter), multi-objects (at least 20) integral-field spectrograph (R>4000) for the E-ELT.
The top level requirements are to concentrate 30 to 40 % of the photons collected by the E-ELT in a focal area of
75x75 mas2 in H band. This leads to the selection of the Multi Object Adaptive Optics in order to deliver such a
performance in a so-large FoV. In this paper, we present a detailed analysis of the error budget for an MOAO system in
EAGLE. It is based on numerical simulation results. The budget is splitted in LGS and NGS contributions. The analysis
leads to share the specifications between low spatial frequencies and high spatial frequencies in the wave-front errors.
Finally a preliminary conceptual design of the MOAO system is deduced including 9 LGS for tomography and a 9000
actuator deformable mirror per channel.
EAGLE is an instrument under conceptual study for the European Extremely Large Telescope (E-ELT). EAGLE will be
installed at the Gravity Invariant Focal Station of the E-ELT, covering a field of view between 5 and 10 arcminutes. Its
main scientific drivers are the physics and evolution of high-redshift galaxies, the detection and characterization of first-light
objects and the physics of galaxy evolution from stellar archaeology. The top level requirements of the instrument
call for 20 spectroscopic channels in the near infrared, assisted by Adaptive Optics. Several concepts of the Target
Acquisition sub-system have been studied and are briefly presented. Multi-Conjugate Adaptive Optics (MCAO) over a
segmented 5' field has been evaluated and compared to Multi-Object Adaptive Optics (MOAO). The latter has higher
performance and is easier to implement, and is therefore chosen as the baseline for EAGLE. The paper provides a status
report of the conceptual study, and indicates how the future steps will address the instrument development plan due to be
completed within a year.
We describe the optical alignment and image quality testing of Michelle, the all-reflective mid-IR astronomical spectrometer and imager being built at the Royal Observatory Edinburgh for the UKIRT and GEMINI telescopes. The design strategy called for optical alignment by manufacture, with the only means for adjustment being the machining of sacrificial pads under key optical components. The success of this approach in meeting the alignment error budget is discussed, including the description of a method for identifying the optical axis of the optical train using field rotation. We present the result of image spot and wavefront error measurements and compare them with the instruments opto-mechanical specification.
Michelle is a facility-class long-slit spectrometer for the mid- IR being built at the Royal Observatory Edinburgh for the UK Infrared Telescope (UKIRT). With diamond turned, all-reflective optics to achieve high throughput and a cryogenic mechanism to select one from five diffraction gratings during operation, it will be capable of taking spectra at resolving powers ranging from 100 to 30,000 over wavelengths from 8 to 25 micrometers . A separate optical path will provide the ability to switch in well under a minute from spectroscopy to taking fully sampled diffraction limited images of the same field. Two mechanical coolers will maintain its optics at below 25K, while a Joule- Thomson (JT) stage on one of the coolers will keep the Si:As hybrid detector array at less than 10K. We present the predicted performance of the instrument, along with its opto-mechanical layout and the means by which it can be easily converted for use on the proposed Gemini telescope. The design of some unusual mechanisms is discussed.