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4MOST is a new high-multiplex, wide-field spectroscopic survey facility under construction for ESO's 4m-VISTA telescope at Paranal, Chile. Its key specifications are: a large field of view of 4.4 square degrees, a high multiplex fibre positioner based on the tilting spine principle that positions 2436 science fibres in the focal surface of which 1624 fibres go to two low-resolution optical spectrographs (R = lambda/Delta lambda similar to 6500) and 812 fibres transfer light to the high-resolution optical spectrograph (R similar to 20,000). Currently, almost all subsystems are completed and full testing in Europe will be finished in spring 2023, after which 4MOST will be shipped to Chile. An overview is given of instrument construction and capabilities, the planned science of the consortium and the recently selected community programmes, and the unique operational scheme of 4MOST.

A uniformly excited slotted waveguide (WG) antenna array for point-to-point communication is presented. The European Telecommunications Standards Institute class-II sidelobe level requirements are satisfied in all planes at almost all frequencies by the aperiodic arrangement of several parallel ridge WGs in the E-plane, each with a different number of equally spaced radiating slots along the H-plane. Both the optimal separation and number of slots per WG are determined through a compressive sensing approach. This results in 160 slots organized in 16 columns offering 29 dBi peak gain at Ka-band. A dedicated 16-way analog beamforming network is designed to provide the optimal nonuniform and in-phase excitation of the 16 WG channels, thereby compensating for the variable number of slots per column and the phase difference due to the E-plane aperiodicity. The measurements confirm the simulated reflection coefficient and radiation pattern characteristics, as well as the high aperture efficiency (70%-90%) over a 13.6% relative bandwidth (27.5-31.5 GHz) and

A status overview of 4MOST is presented, a new high-multiplex, wide-field spectroscopic survey facility under construction for ESO's VISTA telescope at Paranal. Its key specifications are: a large field of view of 4.4 deg2 and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R = λ/Δλ ~ 6500), and 812 fibres transferring light to the high-resolution spectrograph (R ~ 20 000). The 4MOST system integration has commenced and the selection process for ESO community survey programmes has been started. This overview presents the expected performance of the instrument, the science the consortium expects to carry out, and the unique operational scheme of 4MOST.

In recent years, thermal management of FPGAs has attracted extensive scientific attention. However, the majority of proposed cooling solutions remain in research phase with prototypes not addressing the dynamic thermal needs of the full hardware configuration. In this work we present the design and fabrication of a full-board, direct liquid cooling, heat sink for densely packed FPGA-based processing boards. The liquid cooling heat sink design forms part of the high power consuming Gemini Line Replaceable Unit (LRU) processing board, developed for the Square Kilometre Array (SKA) low-frequency aperture array correlator and beam former (CBF). To test the cooling capabilities, in-house developed “heater-firmware” is used to generate 121 watt inside the FPGA and another 85 watt in peripheral heat sources. The presented results show that this direct liquid cooling solution is an efficient thermal design, not only suitable for large quantity production, but also for integration into a dense implementation of 12 Xilinx Ultrascale+ FPGA LRU boards in a standard sub-rack of 178x483x415mm. This configuration enables a processing capacity of 3.4 TMAC/s, while maintaining the die temperature of all FPGAs at a $60.6^{\circ}\mathrm{C}$ level with a water supply temperature of $33^{\circ}\mathrm{C}$.

We describe the Zurich Imaging Polarimeter (ZIMPOL), the visual focal plane subsystem of the SPHERE "VLT planet finder", which pushes the limits of current AO systems to shorter wavelengths, higher spatial resolution, and much improved polarimetric performance. We provide new benchmarks for the performance of high contrast instruments, in particular for polarimetric differential imaging. We have analyzed SPHERE/ZIMPOL point spread functions and measure the peak surface brightness, the encircled energy, and the full width half maximum (FWHM) for different wavelengths, atmospheric conditions, star brightness, and instrument modes. Coronagraphic images are described and analized and the performance for different coronagraphs is compared with tests for the binary alpha Hyi with a separation of 92 mas and a contrast of 6 mag. For the polarimetric mode we made the instrument calibrations using zero polarization and high polarization standard stars and here we give a recipe for the absolute calibration of polarimetric data. The data show a small, 38 pages with 33 figurs, accepted for publication in Astron. Astrophys

Product Assurance is an essential activity to support the design and construction of complex instruments developed for major scientific programs. The international size of current consortia in astrophysics, the ambitious and challenging developments, make the product assurance issues very important. The objective of this paper is to focus in particular on the application of Product Assurance Activities to a project such as MOSAIC, within an international consortium. The paper will also give a general overview on main product assurance tasks to be implemented during the development from the design study to the validation of the manufacturing, assembly, integration and test (MAIT) process and the delivery of the instrument.

International audience

WEAVE is a new wide-field spectroscopy facility proposed for the prime focus of the 4.2m William Herschel Telescope. The facility comprises a new 2-degree field of view prime focus corrector with a 1000-multiplex fibre positioner, a small number of individually deployable integral field units, and a large single integral field unit. The IFUs (Integral Field Units) and the MOS (Multi Object Spectrograph) fibres can be used to feed a dual-beam spectrograph that will provide full coverage of the majority of the visible spectrum in a single exposure at a spectral resolution of ~5000 or modest wavelength coverage in both arms at a resolution ~20000. The instrument is expected to be on-sky by the first quarter of 2018 to provide spectroscopic sampling of the fainter end of the Gaia astrometric catalogue, chemical labeling of stars to V~17, and dedicated follow up of substantial numbers of sources from the medium deep LOFAR surveys. After a brief description of the Fibre System, we describe the fibre test bench, its calibration, and some test results. We have to verify 1920 fibres from the MOS bundles and 740 fibres from the mini-IFU bundles with the test bench. In particular, we present the Focal Ratio Degradation of a cable.

The 4MOST([1]) 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 >25x10(6) 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 similar to 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 similar to 1600 targets at R similar to 5,000 from 390-900nm and similar to 800 targets at R>18,000 in three channels between similar to 395-675nm (channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of similar to 4.1 degrees2. The initial 5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: opto-mechanical, control, data management and operations concepts; and initial performance estimates.

WEAVE is the next-generation optical spectroscopy facility for the William Herschel Telescope and aims at spectroscopic follow-up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE places in the re-fitted prime focus either 1000 fibres, 20 fibre-coupled mini-IFUs or a single large 600 fibre IFU. A spectrograph on the Nasmyth platform analyses the light and supports, in a single exposure, either R~5,000 observations over the full 366- 975 nm wavelength range or simultaneous R~20,000 observations over two out of three pre-specified bands within this wavelength range. This paper describes the requirements, optical design and mechanical design of the WEAVE spectrograph.

Polarimetry is a particularly powerful technique when imaging circumstellar environments. Currently most telescopes include more or less advanced polarimetric facilities and large telescopes count on it for their planet-finder instruments like SPHERE-ZIMPOL on the VLT or EPICS on the future E-ELT. One of the biggest limitations of this technique is the instrumental polarization (IP) generated in the telescope optical path, which can often be larger than the signal to be measured. In most cases this instrumental polarization changes over time and is dependent on the errors affecting the optical elements of the system. We have modeled the VLT and E-ELT telescope layouts to characterize the instrumental polarization generated on their optical paths using the M&m's code, an error budget and performance simulator for polarimetric systems. In this study we present the realistic Mueller matrices calculated with M&m's for both systems, with and without the setups to correct for the IP, showing that correction can be achieved, allowing for an accurate polarimetric performance.

ZIMPOL is an imaging polarimeter for the high contrast SPHERE/VLT "planet finder" instrument using fast polarization modulation and demodulating CCD detectors. The polarimetric performance of the ZIMPOL instrument depends on the polarimetric alignment and quality of the polarization components. This paper gives an overview on the polarimetric concept and the calibration plan of ZIMPOL. We discuss in particular the alignment of the polarimetric calibration components and the polarimetric properties of the ferro electric liquid crystal (FLC) modulator package used in ZIMPOL. Our measurements demonstrate the good broad band performance of the modulator. Faint targets like extra solar planets require mainly a high polarimetric efficiency while for detailed studies of bright targets a good characterization of the modulator package is essential. Therefore we quantify in detail the wavelength dependence of the polarimetric efficiency and the cross talk effects which have to be taken into account in the calibration and data reduction process of high S/N measurements.© (2012) COPYRIGHT Society of Photo Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

X-shooter is the first 2nd generation instrument of the ESO Very Large Telescope(VLT). It is a very efficient, single-target, intermediate-resolution spectrograph that was installed at the Cassegrain focus of UT2 in 2009. The instrument covers, in a single exposure, the spectral range from 300 to 2500 nm. It is designed to maximize the sensitivity in this spectral range through dichroic splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate spectral resolution (R~4,000 - 17,000, depending on wavelength and slit width) with fixed echelle spectral format (prism cross-dispersers) in the three arms. It includes a 1.8"x4" Integral Field Unit as an alternative to the 11" long slits. A dedicated data reduction package delivers fully calibrated two-dimensional and extracted spectra over the full wavelength range. We describe the main characteristics of the instrument and present its performance as measured during commissioning, science verification and the first months of science operations., accepted for publication in A&A

MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) will be a mid-infrared spectro-interferometer combining the beams of up to four telescopes of the European Southern Observatory Very Large Telescope Interferometer (ESO VLTI), providing phase closure and image reconstruction. Matisse will produce interferometric spectra in the LM and in the N band (2.3 to 13.5 micron) and is as such a successor of MIDI. The instrument will be developed by a consortium consisting of Observatoire de Nice (warm optics), NOVA-ASTRON (cold optics), MPI-A (cryostats) and MPIfR (detectors). Beams of up to four Unit Telescopes or Auxiliary Telescopes (UT - AT) pass the warm pre-optics and in the cold optics all beams recombine on the detector where they create a spectral interference pattern. An innovative MAIT plan drastically shortens the MAIT phase and therefore reduces cost. The MAIT plan comprises the assembly and alignment procedure of about 220 cryogenic optical components for which a mirror mount clip has been developed. Alignment accuracy and stability specifications are of the order of nanometers and arcsec, which requires over 50 degrees of freedom in cryogenic alignment mechanisms for e.g. Tip/Tilt and detector Tip/Tilt/Focus. The design, realization and test results of these mechanisms are presented. A cryogenic electrical switch significantly reduces the complexity of the electronic cabling and improves reliability.

SPHERE, the ESO extra-solar planet imager for the VLT is aimed at the direct detection and spectral characterization of extra-solar planets. Its whole design is optimized towards reaching the highest contrast in a limited field of view and at short distances from the central star. SPHERE has passed its Final Design Review (FDR) in December 2008 and it is in the manufacturing and integration phase. We review the most challenging specifications and expected performance of this instrument; then we present the latest stage of the design chosen to meet the specifications, the progress in the manufacturing as well as the integration and test strategy to insure gradual verification of performances at all levels.

This paper presents the specifications, design, construction and evaluation of a piezo-driven tip/tilt/focus mechanism which can align a detector or any other optical component in a cryogenic environment. Even with a no-adjustment design philosophy, usually one or two components have to be adjusted in order to compensate for the total of optical and mechanical tolerances in an optical cryogenic instrument. Normally these adjustments are made by means of shims or stiff screw mechanisms and are applied at room temperature. In order to adjust the particular component(s), mostly by just a few microns, the high-risk and time-consuming operation of opening a cryostat is required. For a large cryostat the typical cycle of cooling, testing, warm-up, opening, adjustment, closing and cooling again, takes roughly two weeks. Often the cycle needs to be repeated a few times before the required position is obtained. ASTRON developed a piezo driven tip/tilt/focus mechanism which can adjust a detector or any other optical component in both the ambient and cryogenic (

During the last ten years, Astron has been a major contractor for the design and manufacturing of astronomical instruments for Space- and Earth based observatories, such as VISIR, MIDI, SPIFFI, X-Shooter and MIRI. Driven by the need to reduce the weight of optically ultra-stiff structures, two promising techniques have been developed in the last years: ASTRON Extreme Lightweighting [1][2] for mechanical structures and an improved Polishing Technique for Aluminum Mirrors. Using one single material for both optical components and mechanical structure simplifies the design of a cryogenic instrument significantly, it is very beneficial during instrument test and verification, and makes the instrument insensitive to temperature changes. Aluminum has been the main material used for cryogenic optical instruments, and optical aluminum mirrors are generally diamond turned. The application of a polishable hard top coating like nickel removes excess stray light caused by the groove pattern, but limits the degree of lightweighting of the mirrors due to the bi-metal effect. By directly polishing the aluminum mirror surface, the recent developments at Astron allow for using a non-exotic material for light weighted yet accurate optical mirrors, with a lower surface roughness (~1nm RMS), higher surface accuracy and reduced light scattering. This paper presents the techniques, obtained results and a global comparison with alternative lightweight mirror solutions. Recent discussions indicate possible extensions of the extreme light weight technology to alternative materials such as Zerodur or Silicon Carbide.

The SPHERE is an exo-solar planet imager, which goal is to detect giant exo-solar planets in the vicinity of bright stars and to characterize them through spectroscopic and polarimetric observations. It is a complete system with a core made of an extreme-Adaptive Optics (AO) turbulence correction, pupil tracker and interferential coronagraphs. At its back end, an Infra-Red Dual-beam Imaging and Spectroscopy science module and an integral field spectrograph work in the Near Infrared (NIR) Y, J, H and Ks bands (0.95 - 2.32μm) and a high resolution polarization camera covers the visible (0.6 - 0.9 μm) region. We describe briefly the science goals of the instrument and deduce the top-level requirements. This paper presents the system architecture, and reviews each of the main sub-systems. The results of the latest end-to-end simulations are shown and an update of the expected performance is given. The project has been officially kicked-off in March 2006, it is presently undergoing Preliminary Design Review and is scheduled for 1st light in early 2011. This paper reviews the present design of SPHERE but focuses on the changes implemented since this project was presented the last time to this audience.

Ground-based and Airborne instrumentation for Astronomy, eds. I. S. McLean and M. Iye, SPIE Proc. 6269, p. 62690Q (2006); International audience

The GLAS (Ground-layer Laser Adaptive-optics System) project is to construct a common-user Rayleigh laser beacon that will work in conjunction with the existing NAOMI adaptive optics system, instruments (near IR imager INGRID, optical integral field spectrograph OASIS, coronagraph OSCA) and infrastructure at the 4.2-m William Herschel Telescope (WHT) on La Palma. The laser guide star system will increase sky coverage available to high-order adaptive optics from ~1% to approaching 100% and will be optimized for scientific exploitation of the OASIS integral-field spectrograph at optical wavelengths. Additionally GLAS will be used in on-sky experiments for the application of laser beacons to ELTs. This paper describes the full range of engineering of the project ranging through the laser launch system, wavefront sensors, computer control, mechanisms, diagnostics, CCD detectors and the safety system. GLAS is a fully funded project, with final design completed and all equipment ordered, including the laser. Integration has started on the WHT and first light is expected summer 2006.

Multi-object instruments provide an increasing challenge for pick-off technology (the means by which objects are selected in the focal plane and fed to sub-instruments such as integral field spectrographs). We have developed a technology demonstrator for a new pick-off system. The performance requirements for the demonstrator have been driven by the outline requirements for possible ELT instruments and the science requirements based on an ELT science case. The goals for the pick-off include that the system should capable of positioning upwards of one hundred pick-off mirrors to an accuracy better than 5 microns. Additionally, the system should be able to achieve this for a curved focal surface -- in this instance with a radius of curvature of 2m. This paper presents the first experimental results from one of the approaches adopted within the Smart Focal Plane project -- that of a Planetary Positioning System. This pick-and place system is so called because it uniquely uses a combination of three rotation stages to place a magnetically mounted pick-off mirror at any position and orientation on the focal surface. A fixed angular offset between the two principal rotation stages ensures that the pick-off mirror is always placed precisely perpendicular to the curved focal plane. The pick-off mirror is gripped and released by a planar micromechanical mechanism which is lowered and raised by a coil-actuated linear stage.

X-shooter, the first 2nd generation VLT instrument, is a new high-efficiency echelle spectrograph. X-shooter operates at the Cassegrain focus and covers an exceptionally wide spectral range from 300 to 2500 nm in a single exposure, with an intermediate spectral resolving power R~5000. The instrument consists of a central structure and three prism crossdispersed echelle spectrographs optimized for the UV-blue, visible and near-IR wavelength ranges. The design of the near-IR arm of the X-shooter instrument employs advanced design methods and manufacturing techniques. Integrated system design is done at cryogenic working temperatures, aiming for an almost alignment-free integration. ASTRON Extreme Light Weighting is used for high stiffness at low mass. Bare aluminium is post-polished to optical quality mirrors, preserving high shape accuracy at cryogenic conditions. Cryogenic optical mounts compensate for CTE differences of various materials, while ensuring high thermal contact. This paper addresses the general design and the application of these specialized techniques.

The PRIMA facility will implement dual-star astrometry at the VLTI. We have formed a consortium that will build the PRIMA differential delay lines, develop an astrometric operation and calibration plan, and deliver astrometric data reduction software. This will enable astrometric planet surveys with a target precision of 10μas. Our scientific goals include determining orbital inclinations and masses for planets already known from radial-velocity surveys, searches for planets around stars that are not amenable to high-precision radial-velocity observations, and a search for large rocky planets around nearby low-mass stars.

Producing extreme light weighted structures by combining a new design concept with the most recent production machines and production software tools. Weight reductions of up to 50% compared to the traditional techniques are feasible with the same stiffness performance. Suitable for standard materials like aluminium and steel, for single construction parts out of mono material and with a single production process. Astronomical instruments for space applications and ground-based applications require more and more extreme light and extreme stiff structures. The traditional technique like 3-axis or multisided machining of metal parts seems limited and not suitable for the next generation instruments. New materials with new production technologies are used more and more with all their specialties and restrictions. ASTRON developed a new structural design of traditional materials with heritage optimized for production with the most recent milling machines. The structural shapes are closely linked to the extremes of 5-axis simultaneous milling. The design and production process is patented and now free for publication.

In this paper, we present the status of VISIR, the mid-infrared instrument to be installed in 2003 at theCassegrain focus of MELIPAL, one of the four 8-meter telescopes of the European Very Large Telescope. Thiscryogenic instrument, optimized for diffraction-limited performance in both mid-infrared atmospheric windows(N and Q band), combines imaging capabilities over a field up to about 1x1 arcmin 2 , and long-slit (0.5 arcmin)grating spectroscopy with various spectral resolutions up to R=25000 at 10 m and 12500 at 20 m. Thecontract to design and build VISIR was signed in November 1996 between the European Southern Observatory(ESO) and a French-Dutch consortium of institutes led by Service d'Astrophysique of Commissariat a l'EnergieAtomique (CEA). A key step in the project has been passed in December 2001, with the first infrared images inthe laboratory and in April 2002 with the first infrared spectra in the laboratory. We present the results of thelaboratorytests of the instrument, which is scheduled to be shipped to Paranal at the end of 2002.Keywords : infrared, instrumentation, imager, spectrometer, VLT.

SPHERE (Spectro-Polarimetric High Contrast Exoplanet Research) is one of the first instruments which aim for the direct detection from extra-solar planets. SPHERE commissioning is foreseen in 2013 on the VLT. ZIMPOL (Zurich Imaging Polarimeter) is the high contrast imaging polarimeter subsystem of the ESO SPHERE instrument. ZIMPOL is dedicated to detect the very faint reflected and hence polarized visible light (600-900 nm) from extrasolar planets. It is located behind an extreme AO system (SAXO) and a stellar coronagraph. We present the first high contrast polarimetric results obtained for the fully integrated SPHERE-ZIMPOL system. We have measured the polarimetric high contrast performance of several coronagraphs: a Classical Lyot on substrate, a suspended Classical Lyot and two 4 Quadrant Phase Mask coronagraphs. We describe the impact of crucial system parameters – Adaptive Optics, Coronagraphy and Polarimetry - on the contrast performance.

We present an overview of the 4MOST project at the Preliminary Design Review. 4MOST is a major new wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of ESO. 4MOST has a broad range of science goals ranging from Galactic Archaeology and stellar physics to the high-energy physics, galaxy evolution, and cosmology. Starting in 2021, 4MOST will deploy 2436 fibres in a 4.1 square degree field-of-view using a positioner based on the tilting spine principle. The fibres will feed one high-resolution (R similar to 20,000) and two medium-resolution (R similar to 5000) spectrographs with fixed 3-channel designs and identical 6k x 6k CCD detectors. 4MOST will have a 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. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept, showing that we can expect to observe more than 25 million objects in each 5-year survey period and will eventually be used to plan and conduct the actual survey.

International audience