MICADO will enable the ELT to perform diffraction limited near-infrared observations at first light. The instrument’s capabilities focus on imaging (including astrometric and high contrast) as well as single object spectroscopy. This contribution looks at how requirements from the observing modes have driven the instrument design and functionality. Using examples from specific science cases, and making use of the data simulation tool, an outline is presented of what we can expect the instrument to achieve.
MICADO will equip the ELT with a first light capability for diffraction limited imaging at near-infrared wave- lengths. The instrument’s observing modes focus on various flavours of imaging, including astrometric, high contrast, and time resolved. There is also a single object spectroscopic mode optimised for wavelength coverage at moderately high resolution.1 Due to ESO’s technology standards evolution from VLT to ELT, MICADO will manifest the combined, PLC based soft- and hardware control. The evolution of ESO’s technology design guidelines is on the one hand triggered by the ongoing developments in modern days industry and consumer tech- nology. On the other hand, ELT’s sheer dimensions request increasingly complex and smart solutions onwards controlling and monitoring such huge instruments. ESO’s control concept is based on a two layer approach: PLCs are responsible for low-level hardware control (in a real-time fashion, if necessary), while software running on a Linux workstation implements the astronomic business logic of the control system. Development is eased by the fact that ESO delivers libraries for the control of many standard hardware components. A very interesting feature of this approach is the possibility to run C++ code natively inside a PLC real-time environment. This will be used for the control of complex mechanisms like the MICADO Atmoshperic Dispersion Corrector (ADC).
This contribution provides an overview of the key functionality of the instrument focusing on the mechanisms inside the cryostat, and an overview of the cryogenic control. Because of hardware and cryogenic safety reasons, the cryostat control PLC system will be designed as a closed PLC based control system. Hence commands will only be accepted from a human machine interface located next to the cryostat itself. All cryostat parameters and according sensor readings will be published via OpcUA, allowing for full remote cryostat monitoring. In contrast, the instrument control PLC system will interact with the higher level software using the advantages of the industrial OpcUA communication standard and will therefore allow for remote control. Further configuration and commissioning of those mechanisms is made conveniently accessible via this approach. All this is based on ESO’s concept for Line replaceable Units (LRU), which utilizes Beckhoff PLC units to ensure maintainability, availability.
We present the new LN2 continuous- ow test cryostat of the Universitats-Sternwarte Munchen, procured within the context of the Multi-Adaptive Optics Imaging Camera for Deep Observations (MICADO) for the Extremely Large Telescope. The cryostat will be used to perform tests of mechanical, optical and electronic components at high vacuum condition and cryogenic temperature, for the development of the cryogenic Main Selection Mechanism of the MICADO instrument. In this paper we give an overview of the cryostat design and we report about the temperature stability the cryostat can achieve, as well as the temperature gradient over its cold plate. We also report about the impact of adding extra loads on the system after integrating a cold curved shutter in the cryostat and on characterizing the thermal coupling of cryogenic assemblies.
MICADO, the Multi AO Imaging Camera for Deep Observations, is one of the first light instruments for the ELT, currently under construction by the European Southern Observatory (ESO) on Cerro Armazones in Chile. It is built by a huge consortium with partners from the Netherlands, Austria, France, Italy, Finland and Germany under the lead of the Max-Planck-Institute for extraterrestrial Physics in Garching. The instrument will operate in the NIR wavelength range, thus is developed as a cryogenic instrument to work under vacuum conditions. It can be used as an imaging camera in a high and low resolution mode, a spectrometer and also as a coronagraph. For calibration purposes a so called ”pupil imager” mode will also be implemented. To switch between the operational modes MICADO will use the MSM to insert different optical modules to the fixed components of the High Resolution Imager (HRI) inside the cryostat. All moving parts have to operate under vacuum and at cryogenic temperatures. The MSM consists of a rotating platform, where the optical modules are mounted on. To lower the friction inside the mechanism we decided to use several small bearings to support the platform instead of a central big one. The small bearings are placed in a way, that the movement of the platform is limited to a rotation. Some of the bearings will be preloaded by springs to take also CTE differences or temperature gradients during the cool down and warm up phases into account. The mechanism will be driven by a cryogenic Phytron stepper motor with an integrated planetary gear box. Switches will be used to limit the rotation of the platform to the necessary range. Because of the challenging requirements on repositioning of the optical modules inside the science beam, we will use an indent mechanism. We are still investigating if the indent mechanism has to be actively driven or can be implemented as a passive version. The necessary optics to switch between the operational modes are designed as individual pre-aligned modules, each with a defined mechanical and thermal interface to the rotating platform. The Low Resolution Imager (LRI) consists of two flat mirrors, blocking some of the fixed components of the HRI. The spectrometer will use two reflective gratings, one acting as the main and one as a cross disperser. The cross disperser separates the overlaying orders on the focal plane array. The pupil viewer consists like the LRI module of two flat mirrors and an additional lens imaging the pupil to the focal plane. In this paper we will present the current mechanical design and first results of the structural and thermal FEM analyses we performed. We will also highlight first ideas on integration and alignment. A second paper (A. Monna et al., same proceedings) concentrates on the cryogenic setups we perform inside a cryostat to proof proper functionality of the chosen components and designs.
MICADO will equip the E-ELT with a first light capability for diffraction limited imaging at near-infrared wavelengths. The instrument’s observing modes focus on various flavours of imaging, including astrometric, high contrast, and time resolved. There is also a single object spectroscopic mode optimised for wavelength coverage at moderately high resolution. This contribution provides an overview of the key functionality of the instrument, outlining the scientific rationale for its observing modes. The interface between MICADO and the adaptive optics system MAORY that feeds it is summarised. The design of the instrument is discussed, focusing on the optics and mechanisms inside the cryostat, together with a brief overview of the other key sub-systems.
The Ludwig-Maximilians-Universität München operates an astrophysical observatory on the summit of Mt. Wendelstein which was equipped with a modern 2m-class robotic telescope in 2011<sup>1-3</sup>. One of the two Nasmyth ports is designed to deliver the excellent (< 0.8” median) seeing of the site for a FoV of 60 arcmin<sup>2</sup> without any corrector optics at optical and near infrared (NIR) wavebands. This port hosts a three channel imager whose design was already presented in Lang-Bardl et al. 2010.<sup>4</sup> It is designed to efficiently support observations of targets of opportunities like Gamma-Ray-bursts or efficient photometric
redshift determination of sources identified by surveys like PanSTARS, Planck (SZ) or eROSITA. The covered wavelength range is 340 nm to 2.3 microns. The camera provides standard broadband filters (Sloan, Y, J, H, Ks) and 5 narrowband filters (OI, Hα, SII, H<sub>2</sub>, Br<sub>λ</sub>). The narrowband filters will enable deep studies of star forming regions. We present the final design of the camera, the assembly and alignment procedure performed in the laboratory before we transported the instrument to the observatory. We also show first results of the achieved on sky performance concerning image quality and efficiency of the camera in the different filter passbands.
We present a Θ - Φ-style fiber-positioner prototype, which will be controlled via the EMI-robust CAN-Bus. Our positioner points without iterations or a metrology system. Due to the overlapping patrol disc of 17.3 mm diameter, we reach a filling factor of 100 %. The positioners diameter is 14.6 mm, containing the control electronics on a contemporary PCB of 13.5 mm width. While moving, the power consumption does not lead to a significant rise in temperature. Given a mechanical reference point measured by stall detection, the absolute accuracy is 27 μm (1σ = 14 µm) and pointings are repeatable with 7 μm (1σ = 4 μm). Better positioning may be reachable with upcoming calibration.
The 4MOST instrument is a concept for a wide-field, fibre-fed high multiplex spectroscopic instrument facility on the
ESO VISTA telescope designed to perform a massive (initially >25x106 spectra in 5 years) combined all-sky public
survey. The main science drivers are: Gaia follow up of chemo-dynamical structure of the Milky Way, stellar radial
velocities, parameters and abundances, chemical tagging; eROSITA follow up of cosmology with x-ray clusters of
galaxies, X-ray AGN/galaxy evolution to z~5, Galactic X-ray sources and resolving the Galactic edge;
Euclid/LSST/SKA and other survey follow up of Dark Energy, Galaxy evolution and transients. The surveys will be
undertaken simultaneously requiring: highly advanced targeting and scheduling software, also comprehensive data
reduction and analysis tools to produce high-level data products. The instrument will allow simultaneous observations of
~1600 targets at R~5,000 from 390-900nm and ~800 targets at R<18,000 in three channels between ~395-675nm
(channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of ~ 4.1 degrees. The initial
5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: optomechanical,
control, data management and operations concepts; and initial performance estimates.
4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large
area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with ~2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; ~1600 fibres go to two spectrographs with resolution R<5000 (λ~390-930 nm) and
~800 fibres to a spectrograph with R>18,000 (λ~392-437 nm and 515-572 nm and 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the
southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing
concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020.
This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more
detailed descriptions of the instrument concept, the instrument requirements development, the systems engineering implementation, the instrument model, the fibre positioner concepts, the fibre feed, and the spectrographs.
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.
The 4MOST consortium is currently halfway through a Conceptual Design study for ESO with the aim to develop a wide-field ( < 3 square degree, goal < 5 square degree), high-multiplex ( < 1500 fibres, goal 3000 fibres) spectroscopic survey facility for an ESO 4m-class telescope (VISTA). 4MOST will run permanently on the telescope to perform a 5 year public survey yielding more than 20 million spectra at resolution R∼5000 (λ=390–1000 nm) and more than 2 million spectra at R~20,000 (395–456.5 nm and 587–673 nm). The 4MOST design is especially intended to complement three key all-sky, space-based observatories of prime European interest: Gaia, eROSITA and Euclid. Initial design and performance estimates for the wide-field corrector concepts are presented. Two fibre positioner concepts are being considered for 4MOST. The first one is a Phi-Theta system similar to ones used on existing and planned facilities. The second one is a new R-Theta concept with large patrol area. Both positioner concepts effectively address the issues of fibre focus and pupil pointing. The 4MOST spectrographs are fixed configuration two-arm spectrographs, with dedicated spectrographs for the high- and low-resolution fibres. A full facility simulator is being developed to guide trade-off decisions regarding the optimal field-of-view, number of fibres needed, and the relative fraction of high-to-low resolution fibres. The simulator takes mock catalogues with template spectra from Design Reference Surveys as starting point, calculates the output spectra based on a throughput simulator, assigns targets to fibres based on the capabilities of the fibre positioner designs, and calculates the required survey time by tiling the fields on the sky. The 4MOST consortium aims to deliver the full 4MOST facility by the end of 2018 and start delivering high-level data products for both consortium and ESO community targets a year later with yearly increments.
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.
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.
4MOST<sup>1</sup> is a multi object spectrograph facility for ESO’s NTT or VISTA telescope. 4MOST is one of the two projects selected for a conceptual design study by ESO. The 4MOST instrument will be able to position < 1500 fibres in the focal plane and collect spectra in a high resolution (R=20000)<sup>2</sup> and a low resolution (R=5000) mode (HRM, LRM). The spectral coverage for the LRM is 400-900 nm, the HRM covers 390-459 nm and 564-676 nm. We will present one of the possible positioner designs and first tests of some components for the focal plane array. The design follows the LAMOST<sup>3</sup> positioner and has two rotational axes to move the fibre inside the patrol disc. Each axis consists of a stepper motor attached to micro harmonic drive (MHD). The small outer dimensions and high gear ratios of the MHD-stepper motor package, makes them perfectly suitable for our application. The MHD is also backlash free and self-locking what gives us the opportunity to minimize power consumption and heat dissipation during observation without loosing the position of the fibre on sky. The control electronics will also be miniaturized and part of the positioner unit.
The KMOS Instrument is built to be one of the second generation VLT instruments. It is a highly complex multi-object
spectrograph for the near infrared. Nearly 60 cryogenic mechanisms have to be controlled. This includes 24 deployable
Pick-Off arms, three filter and grating wheels as well as three focus stages and four lamps with an attenuator wheel.
These mechanisms and a calibration unit are supervised by three control cabinets based on the VLT standards. To follow
the rotation of the Nasmyth adaptor the cabinets are mounted into a Co-rotating structure. The presentation will highlight
the requirements on the electronics control and how these are met by new technologies applying a compact and reliable
signal distribution. To enable high density wiring within the given space envelope flex-rigid printed circuit board designs
have been installed. In addition an electronic system that detects collisions between the moving Pick-Off arms will be
presented for safe operations. The control system is designed to achieve two micron resolution as required by optomechanical
and flexure constraints. Dedicated LVDT sensors are capable to identify the absolute positions of the Pick-
Off arms. These contribute to a safe recovery procedure after power failure or accidental collision.
MICADO is the adaptive optics imaging camera for the E-ELT. It has been designed and optimised to be mounted
to the LGS-MCAO system MAORY, and will provide diffraction limited imaging over a wide (~1 arcmin) field
of view. For initial operations, it can also be used with its own simpler AO module that provides on-axis
diffraction limited performance using natural guide stars. We discuss the instrument's key capabilities and
expected performance, and show how the science drivers have shaped its design. We outline the technical
concept, from the opto-mechanical design to operations and data processing. We describe the AO module,
summarise the instrument performance, and indicate some possible future developments.
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.
KMOS is a near-infrared multi-object integral field spectrometer which has been selected as one of a suite of second-generation instruments to be constructed for the ESO VLT in Chile. The instrument will be built by a consortium of UK and German institutes working in partnership with ESO and is currently at the end of its preliminary design phase. We present the design status of KMOS and discuss the most novel technical aspects and the compliance with the technical specification.
A 16K x 16K, 1 degree x 1 degree field, detector system was developed by ESO for the OmegaCAM instrument for use on the purpose built ESO VLT Survey Telescope (VST). The focal plane consists of an 8 x 4 mosaic of 2K x 4K 15um pixel e2v CCDs and four 2K x 4K CCDs on the periphery for the opto-mechanical control of the telescope. The VST is a single instrument telescope. This placed stringent reliability requirements on the OmegaCAM detector system such as 10 years lifetime and maximum downtime of 1.5 %. Mounting at Cassegrain focus required a highly autonomous self-contained cooling system that could deliver 65 W of cooling power. Interface space for the detector head was severely limited by the way the instrument encloses the CCD cryostat. The detector system features several novel ideas tailored to meet these requirements and described in this paper:
Key design drivers of the detector head were the easily separable but precisely aligned connections to the optical field flattener on the top and the cooling system at the bottom. Material selection, surface treatment, specialized coatings and in-situ plasma cleaning were crucial to prevent contamination of the detectors. Inside the cryostat, cryogenic and electrical connections were disentangled to keep the configuration modular, integration friendly and the detectors in a safe condition during all mounting steps. A compact unit for logging up to 125 Pt100 temperature sensors and associated thermal control loops was developed (ESO's new housekeeping unit PULPO 2), together with several new modular Pt100 packaging and mounting concepts. The electrical grouping of CCDs based on process parameters and test results is explained. Three ESO standardized FIERA CCD controllers in different configurations are used. Their synchronization mechanism for read-out is discussed in connection with the CCD grouping scheme, the shutter, and the integrated guiding and image analysis facility with four independent 2K x 4K CCDs. An illustration of the data chain performance from CCD output to storage on hard-disk gives an impression of the challenge to shift 512 MB of data within 45 seconds via the standardized hierarchical ESO data acquisition network. Finally the safety and emergency features of the overall system are presented.
OmegaCAM is the wide-field camera for the VLT Survey Telescope being
completed for ESO's Paranal observatory. The instrument, as well as the telescope, have been designed for very good, natural seeing-limited image quality over a 1 degree field. At the heart of the project are a square-foot photometric shutter, a 12-filter storage/exchange mechanism, a 16k x 16k CCD detector mosaic, and plenty of software for instrument control and data handling, analysis and archiving.
The FORS instruments are focal reducers and spectrographs which are built in two copies for the unit telescopes UT1 and UT2 of the ESO/VLT by a consortium of University Observatories. An overview of the instrument capabilities is given in a separate paper at this conference.
FORS is an all dioptric focal reducer designed for direct imaging, low-dispersion multi-object spectroscopy, imaging polarimetry and spectropolarimetry of faint objects. Two almost identical copies of the instrument were built by a consortium of three astronomical institutes under contract and in cooperation with ESO. FORS1 was installed in September 1998 and FORS2 in October 1999 at the Cassegrain foci of the ESO VLT unit telescope nos. 1 and 2. FORS1 is in regular operation since April 1999. Regular observation with FORS2 are scheduled to begin in April 2000.
FORS1 (FOcal Reducer/low-dispersion Spectrograph) is an all dioptric focal reducer designed for direct imaging, low- dispersion multi-object spectroscopy, imaging polarimetry and spectro-polarimetry of faint objects. Two identical copies of the instrument (FORS 1 and 2) are being built by a consortium of three astronomical institutes (Landessternwarte Heidelberg and the University Observatories of Gottingen and Munich) under contract and in cooperation with ESO. FORS 1 and 2 will be installed, respectively, in 1998 and 2000 at the Cassegrain foci of the ESO VLT unit telescopes nos. 1 and 2. For the tests of FORS in Europe, a telescope and star simulator was built, which allows to incline and rotate the whole instrument and to simulate stars in the field of view at various seeing conditions. FORS 1 was integrated at the telescope simulator and saw its 'first light' in the integration facility in November 1996. Since then the electro-mechanical functions, the image motion due to flexure, the calibration units, the optical performance and the instrument software were tested and optimized. This paper presents a summary of the procedure and the results of the tests.
One of the most critical issues in designing a spectrograph is the motion of opto-mechanical components due to flexure especially when it will be mounted to the Cassegrain focus of a telescope. Image motion on the detector has to be kept small in order not to affect the value of the scientific data. The FORS spectrographs fulfil those requirements by a proper design and by a passive compensation of the instrumental flexure. Image motion of the 2 metric tons instrument could be reduced in this way to a tiny fraction of one pixel's size thus not affecting the data gathered with those spectrographs. It is tested and approved at a telescope simulator that all specifications regarding those motions are fully met. A fine tuning flexure compensation is built into the spectrograph's design and is tested on its tuning range which allows to adapt the compensation to effects eventually caused by the Cassegrain flange of the telescope.