Search

Observations of metal absorption systems in the spectra of distant quasars allow to constrain a possible variation of the fine-structure constant throughout the history of the Universe. Such a test poses utmost demands on the wavelength accuracy and previous studies were limited by systematics in the spectrograph wavelength calibration. A substantial advance in the field is therefore expected from the new ultra-stable high-resolution spectrograph Espresso, recently installed at the VLT. In preparation of the fundamental physics related part of the Espresso GTO program, we present a thorough assessment of the Espresso wavelength accuracy and identify possible systematics at each of the different steps involved in the wavelength calibration process. Most importantly, we compare the default wavelength solution, based on the combination of Thorium-Argon arc lamp spectra and a Fabry-P\'erot interferometer, to the fully independent calibration obtained from a laser frequency comb. We find wavelength-dependent discrepancies of up to 24m/s. This substantially exceeds the photon noise and highlights the presence of different sources of systematics, which we characterize in detail as part of this study. Nevertheless, our study demonstrates the outstanding accuracy of Espresso with respect to previously used spectrographs and we show that constraints of a relative change of the fine-structure constant at the $10^{-6}$ level can be obtained with Espresso without being limited by wavelength calibration systematics., Comment: 27 pages, accepted for publication in A&A

Aims. We report on ESPRESSO high-resolution transmission spectroscopic observations of two primary transits of the highly-irradiated, ultra-hot Jupiter-size planet WASP-76b. We investigate the presence of several key atomic and molecular features of interest that may reveal the atmospheric properties of the planet. Methods. We extracted two transmission spectra of WASP-76b with R approx 140,000 using a procedure that allowed us to process the full ESPRESSO wavelength range (3800-7880 A) simultaneously. We observed that at a high signal-to-noise ratio, the continuum of ESPRESSO spectra shows wiggles that are likely caused by an interference pattern outside the spectrograph. To search for the planetary features, we visually analysed the extracted transmission spectra and cross-correlated the observations against theoretical spectra of different atomic and molecular species. Results. The following atomic features are detected: Li I, Na I, Mg I, Ca II, Mn I, K I, and Fe I. All are detected with a confidence level between 9.2 sigma (Na I) and 2.8 sigma (Mg I). We did not detect the following species: Ti I, Cr I, Ni I, TiO, VO, and ZrO. We impose the following 1 sigma upper limits on their detectability: 60, 77, 122, 6, 8, and 8 ppm, respectively. Conclusions. We report the detection of Li I on WASP-76b for the first time. In addition, we found the presence of Na I and Fe I as previously reported in the literature. We show that the procedure employed in this work can detect features down to the level of ~ 0.1 % in the transmission spectrum and ~ 10 ppm by means of a cross-correlation method. We discuss the presence of neutral and singly ionised features in the atmosphere of WASP-76b., 20 pages, 19 figures, accepted for publication in Astronomy and Astrophysics

ESPRESSO is the new high-resolution spectrograph of ESO's Very-Large Telescope (VLT). It was designed for ultra-high radial-velocity precision and extreme spectral fidelity with the aim of performing exoplanet research and fundamental astrophysical experiments with unprecedented precision and accuracy. It is able to observe with any of the four Unit Telescopes (UT) of the VLT at a spectral resolving power of 140,000 or 190,000 over the 378.2 to 788.7 nm wavelength range, or with all UTs together, turning the VLT into a 16-m diameter equivalent telescope in terms of collecting area, while still providing a resolving power of 70,000. We provide a general description of the ESPRESSO instrument, report on the actual on-sky performance, and present our Guaranteed-Time Observation (GTO) program with its first results. ESPRESSO was installed on the Paranal Observatory in fall 2017. Commissioning (on-sky testing) was conducted between December 2017 and September 2018. The instrument saw its official start of operations on October 1st, 2018, but improvements to the instrument and re-commissioning runs were conducted until July 2019. The measured overall optical throughput of ESPRESSO at 550 nm and a seeing of 0.65 arcsec exceeds the 10% mark under nominal astro-climatic conditions. We demonstrate a radial-velocity precision of better than 25 cm/s during one night and 50 cm/s over several months. These values being limited by photon noise and stellar jitter show that the performanceis compatible with an instrumental precision of 10 cm/s. No difference has been measured across the UTs neither in throughput nor RV precision. The combination of the large collecting telescope area with the efficiency and the exquisite spectral fidelity of ESPRESSO opens a new parameter space in RV measurements, the study of planetary atmospheres, fundamental constants, stellar characterisation and many other fields., 26 pages, 28 figures

Toledo-Padrón, B. et al., Context. An accurate characterization of the known exoplanet population is key to understanding the origin and evolution of planetary systems. Determining true planetary masses through the radial velocity (RV) method is expected to experience a great improvement thanks to the availability of ultra-stable echelle spectrographs. Aims. We took advantage of the extreme precision of the new-generation echelle spectrograph ESPRESSO to characterize the transiting planetary system orbiting the G2V star K2-38 located at 194 pc from the Sun with V 11.4. This system is particularly interesting because it could contain the densest planet detected to date. Methods. We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets, K2-38b and K2-38c, with Pb = 4.01593 ± 0.00050 d and Pc = 10.56103 ± 0.00090 d, respectively. Using 43 ESPRESSO high-precision RV measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a Markov chain Monte Carlo analysis, significantly improving their mass measurements. Results. Using ESPRESSO spectra, we derived the stellar parameters, Teff = 5731 ± 66, log g = 4.38 ± 0.11 dex, and [Fe/H] = 0.26 ± 0.05 dex, and thus the mass and radius of K2-38, Ma = 1.03-0.02+0.04 MaS and Ra = 1.06-0.06+0.09 RaS. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with RP = 1.54 ± 0.14 RaS and Mp = 7.3-1.0+1.1 MaS, and K2-38c as a sub-Neptune with RP = 2.29 ± 0.26 RaS and Mp = 8.3-1.3+1.3 MaS. Combining the radius and mass measurements, we derived a mean density of ρp = 11.0-2.8+4.1 g cm-3 for K2-38b and ρp = 3.8-1.1+1.8 g cm-3 for K2-38c, confirming K2-38b as one of the densest planets known to date. Conclusions. The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky-model with H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the RV time-series whose origin could be linked to a 0.25-3 MJ planet or stellar activity., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

Damasso, M. et al., Context. The bright star π Men was chosen as the first target for a radial velocity follow-up to test the performance of ESPRESSO, the new high-resolution spectrograph at the European Southern Observatory's Very Large Telescope. The star hosts a multi-planet system (a transiting 4 M· planet at ∼0.07 au and a sub-stellar companion on a ∼2100-day eccentric orbit), which is particularly suitable for a precise multi-technique characterization. Aims. With the new ESPRESSO observations, which cover a time span of 200 days, we aim to improve the precision and accuracy of the planet parameters and search for additional low-mass companions. We also take advantage of the new photometric transits of π Men c observed by TESS over a time span that overlaps with that of the ESPRESSO follow-up campaign. Methods. We analysed the enlarged spectroscopic and photometric datasets and compared the results to those in the literature. We further characterized the system by means of absolute astrometry with HIPPARCOS and Gaia. We used the high-resolution spectra of ESPRESSO for an independent determination of the stellar fundamental parameters. Results. We present a precise characterization of the planetary system around π Men. The ESPRESSO radial velocities alone (37 nightly binned data with typical uncertainty of 10 cm s-1) allow for a precise retrieval of the Doppler signal induced by π Men c. The residuals show a root mean square of 1.2 m s-1, which is half that of the HARPS data; based on the residuals, we put limits on the presence of additional low-mass planets (e.g. we can exclude companions with a minimum mass less than ∼2 M· within the orbit of π Men c). We improve the ephemeris of π Men c using 18 additional TESS transits, and, in combination with the astrometric measurements, we determine the inclination of the orbital plane of π Men b with high precision (ib =45.8-1.1+1.4 deg). This leads to the precise measurement of its absolute mass mb =14.1-0.4+0.5 MJup, indicating that π Men b can be classified as a brown dwarf. Conclusions. The π Men system represents a nice example of the extreme precision radial velocities that can be obtained with ESPRESSO for bright targets. Our determination of the 3D architecture of the π Men planetary system and the high relative misalignment of the planetary orbital planes put constraints on and challenge the theories of the formation and dynamical evolution of planetary systems. The accurate measurement of the mass of π Men b contributes to make the brown dwarf desert a bit greener., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

Context The study of exoplanet atmospheres is essential for understanding the formation, evolution, and composition of exoplanets. The transmission spectroscopy technique is playing a significant role in this domain. In particular, the combination of state-of-The-Art spectrographs at low-And high-spectral resolution is key to our understanding of atmospheric structure and composition. Aims. We observed two transits of the close-in sub-Saturn-mass planet, WASP-127b, with ESPRESSO in the frame of the Guaranteed Time Observations Consortium. We aim to use these transit observations to study the system architecture and the exoplanet atmosphere simultaneously. Methods. We used the Reloaded Rossiter-McLaughlin technique to measure the projected obliquity λ and the projected rotational velocity veq sin(i∗). We extracted the high-resolution transmission spectrum of the planet to study atomic lines. We also proposed a new cross-correlation framework to search for molecular species and we applied it to water vapor. Results. The planet is orbiting its slowly rotating host star (veq sin(i∗) = 0.53-0.05+0.07 km s-1) on a retrograde misaligned orbit (λ =-128.41-5.46+5.60 °). We detected the sodium line core at the 9-σ confidence level with an excess absorption of 0.34 ± 0.04%, a blueshift of 2.74 ± 0.79 km s-1, and a full width at half maximum of 15.18 ± 1.75 km s-1. However, we did not detect the presence of other atomic species but set upper limits of only a few scale heights. Finally, we put a 3-σ upper limit on the average depth of the 1600 strongest water lines at equilibrium temperature in the visible band of 38 ppm. This constrains the cloud-deck pressure between 0.3 and 0.5 mbar by combining our data with low-resolution data in the near-infrared and models computed for this planet. Conclusions. WASP-127b, with an age of about 10 Gyr, is an unexpected exoplanet by its orbital architecture but also by the small extension of its sodium atmosphere (~7 scale heights). ESPRESSO allows us to take a step forward in the detection of weak signals, thus bringing strong constraints on the presence of clouds in exoplanet atmospheres. The framework proposed in this work can be applied to search for molecular species and study cloud-decks in other exoplanets., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

International audience

Departamento deFsica eAstronomia, Faculdade Cincias, Universidade do Porto,Rua das Estrelas, 4150-762PortugalReceived2013 Aug 29, accepted 2013 Nov1Published online 2014 Jan 15Keywords instrumentation: spectrographs –plantary systems –techniques: spectroscopicThe acronym ESPRESSO stems for Echelle SPectrograph for RockyExoplanets and Stable Spectroscopic Observations;this instrument will be the next VLThigh resolution spectrograph. The spectrograph will be installed at the Combined-CoudeL´ aboratory of the VLTand linked to the four 8.2mUnit Telescopes (UT) through four optical Coudet´ rains.ESPRESSO will combine efficiencyand extreme spectroscopic precision. ESPRESSO is foreseen to achieve again oftwomagnitudes with respect to its predecessor HARPS, and to improve the instrumental radial-velocity precision to reachthe 10 cms

The first generation of E-ELT instruments will include an optical-infrared High Resolution Spectrograph, conventionally indicated as EELT-HIRES, which will be capable of providing unique breakthroughs in the fields of exoplanets, star and planet formation, physics and evolution of stars and galaxies, cosmology and fundamental physics. A 2-year long phase A study for EELT-HIRES has just started and will be performed by a consortium composed of institutes and organisations from Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland and United Kingdom. In this paper we describe the science goals and the preliminary technical concept for EELT-HIRES which will be developed during the phase A, as well as its planned development and consortium organisation during the study., 12 pages, in Ground-based and Airborne Instrumentation for Astronomy VI, 2016, Proc. SPIE 9908, 23

ESPRESSO, Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, is now under the assembly, integration and verification phase and will be installed beginning next year at Paranal Observatory on ESO's Very Large Telescopes. The Front End is the modular system in the Combined Coudé Laboratory receiving the light from the four VLT Units, providing the needed connection between the input signal, i.e., object light, sky light, and calibration light, to feed the spectrograph through optical fibers. The modular concept of the FE Units drove the system design and the alignment workflow. We will show the integration method of the single FE modules adopted to guarantee the necessary repeatability between the different Units. The performances of the system in terms of image quality and encircled energy in the observed point spread function are reported. Finally, the strategy followed in the Paranal Combined Coudè Laboratory to define the convergence point of the four UTs is described, along with the procedure used to align the ground plates, the main structure, and the mode selector.

One year of operations demonstrated the high level of scientific performance of the X-shooter spectrograph. The excellent science opened by this instrument is described in various papers within this volume. The purpose of this contribution is to briefly describe the novel technical solution adopted in the design and construction phase of X-shooter that made it a successful instrument and the aforementioned science possible (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper covers the various aspect of design, manufacturing and commissioning of the infrared camera BIRCAM, installed at BOOTES-IR, the 60cm robotic infrared telescope at Sierra Nevada Observatory (OSN, Granada, Spain). We describe how we achieved a quality astronomical image, moving from the scientific requirements. Copyright © 2010 Alberto Riva et al.

MAORY is one of the four instruments for the E-ELT approved for construction. It is an adaptive optics module offering two compensation modes: multi-conjugate and single-conjugate adaptive optics. The project has recently entered its phase B. A system-level overview of the current status of the project is given in this paper.

AMICA (Antarctic Multiband Infrared CAmera) is an instrument designed to perform astronomical imaging in the near- (1-5 μm) and mid- (5–27 μm) infrared wavelength regions. Equipped with two detectors, an InSb 2562 and a Si:As 1282 IBC, cooled at 35 and 7 K respectively, it will be the first instrument to investigate the potential of the Italian-French base Concordia for IR astronomy. The main technical challenge is represented by the extreme conditions of Dome C (T ~ -90 °C, p ~ 640 mbar). An environmental control system ensures the correct start-up, shut-down and housekeeping of the various components of the camera. AMICA will be mounted on the IRAIT telescope and will perform survey-mode observations in the Southern sky. The first task is to provide important site-quality data. Substantial contributions to the solution of fundamental astrophysical quests, such as those related to late phases of stellar evolution and to star formation processes, are also expected.

X-shooter is a spectrograph designed to feed the Cassegrain focus of the VLT. It may cover in a single exposure the spectral range from the UV to the H band with possible extension to the K band. The instrument is constituted by three arms, blue, visible and near-infarred, with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate resolution (R = 4000−14 000), sufficient to address quantitatively a vast number of astrophysical applications. Approved as second generation instrument for the VLT, X-shooter is expected to be available to the community in the first part of the year 2008.

The REM Observatory, recently installed and commissioned at la Silla Observatory Chile, is the first moderate aperture robotic telescope able to cover simultaneously the visible-NIR (0.45-2.3 microns) wavelength range. Due to its very fast pointing and its full robotization REM is conceived for fast transients observation. The high throughput Infrared Camera (REMIR) and the Visible imaging spectrograph (ROSS), simultaneously fed by a dichroic, allow to collect high S/N data in an unprecedented large spectral range on a telescope of this size. The REMobservatory is an example of a versatile and agile facility necessary complement to large telescopes in fields in which rapid response and/or target pre-screening are necessary. This paper describes the principal Characteristics and operation modes of the REM observatory and gives on overview of the preliminary results obtained during the commissioning phase. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In a cosmological context dust has been always poorly understood. That is true also for the statistic of GRBs so that we started a program to understand its role both in relation to GRBs and in function of z. This paper presents a composite model in this direction. The model considers a rather generic distribution of dust in a spiral galaxy and considers the effect of changing some of the parameters characterizing the dust grains, size in particular. We first simulated 500 GRBs distributed as the host galaxy mass distribution, using as model the Milky Way. If we consider dust with the same properties as that we observe in the Milky Way, we find that due to absorption we miss about 10% of the afterglows assuming we observe the event within about 1 hour or even within 100s. In our second set of simulations we placed GRBs randomly inside giants molecular clouds, considering different kinds of dust inside and outside the host cloud and the effect of dust sublimation caused by the GRB inside the clouds. In this case absorption is mainly due to the host cloud and the physical properties of dust play a strong role. Computations from this model agree with the hypothesis of host galaxies with extinction curve similar to that of the Small Magellanic Cloud, whereas the host cloud could be also characterized by dust with larger grains. To confirm our findings we need a set of homogeneous infrared observations. The use of coming dedicated infrared telescopes, like REM, will provide a wealth of cases of new afterglow observations., Comment: 16 pages, 8 figures, accepted by A&A

Observations of the prompt afterglow of γ-ray burst events are unanimously considered of paramount importance for GRB science and cosmology. Such observations at NIR wavelengths are even more promising allowing the monitoring of high-z Ly-α absorbed bursts as well as events occurring in dusty star-forming regions. In these pages we present rapid eye mount (REM), a fully robotized fast slewing telescope equipped with a high throughput NIR (Z, J, H, K) camera dedicated to detecting the prompt IR afterglow. REM can discover objects at extremely high redshift and trigger large telescopes to observe them. The REM telescope will simultaneously feed REM optical slitless spectrograph (ROSS) via a dichroic. ROSS will intensively monitor the prompt optical continuum of GRB afterglows. The synergy between the REM-IR camera and the ROSS spectrograph makes REM a powerful observing tool for any kind of fast transient phenomena. Beside its ambitious scientific goals, REM is also technically challenging since it represent the first attempt to locate a NIR camera on a small telescope providing, with ROSS, unprecedented simultaneous wavelength coverage on a telescope of this size.

Received ———-; accepted ———— Abstract. A way to fully exploit the large collecting area of modern 8-10m class telescopes is high resolution spectroscopy. Many astrophysical problems from planetary science to cosmology benefit from spectroscopic observations at the highest resolution currently achievable and would benefit from even higher resolutions. Indeed in the era of 8-10m class telescopes no longer the telescope collecting area but the size of the beam — which is related to the maximum size in which reflection gratings are manufactured — is what mainly limits the resolution. A resolution-slit product R' ≃ 40,000 is the maximum currently provided by a beam of 20 cm illuminating the largest grating mosaics. We present a conceptual design for a spectrograph with R' ≃ 80,000, i.e. twice as large as that of existing instruments. Examples of the possible exploitation of such a high R' value, including spectropolarimetry and very high resolution (R ∼ 300, 000), are discussed in detail. The new concept is illustrated through the specific case of a high resolution spectropolarimeter for the Large Binocular Telescope.

The Multi-Conjugate Adaptive Optics module for the European Extremely Large Telescope has been designed to achieve uniform compensation of the atmospheric turbulence effects on a wide field of view in the near infrared. The design realized in the Phase A of the project is undergoing major revision in order to define a robust baseline in view of the next phases of the project. An overview of the on-going activities is presented.

The opto-mechanical conceptual design for the Front-End unit and the calibration unit of the ESPRESSO Spectrograph is described in this paper. The front end system exploits a modular concept. Each FEU receive the beam directly from the relative Telescope Coude Train and the calibration light from the calibration unit. On the other side the FEU feeds the fibers that carry the light to the spectrograph, corresponding in number and size to the scientific observing modes conceived for Espresso. The selection is made through a Toggling Unit. Purpose of the Front/End is to provide the needed connection between the input signal, i.e. Object light, Sky light, Calibration light, and the given output fiber in any of the foreseen observing modes.

International audience; The current instrumentation plan for the E-ELT foresees a High Resolution Spectrograph conventionally indicated as HIRES. Shaped on the study of extra-solar planet atmospheres, Pop-III stars and fundamental physical constants, HIRES is intended to embed observing modes at high-resolution (up to R=150000) and large spectral range (from the blue limit to the K band) useful for a large suite of science cases that can exclusively be tackled by the E-ELT. We present in this paper the solution for HIRES envisaged by the "HIRES initiative", the international collaboration established in 2013 to pursue a HIRES on E-ELT.

ESPRESSO is a fibre-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope), and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT at the Combined Coude Laboratory (CCL), fed by four Coude Trains, which brings the light from the Nasmyth platforms of the four VLT Unit Telescopes to the CCL. ESPRESSO will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach cm/s level. Thanks to its ability of combining incoherently the light of the 4 UTs, ESPRESSO will offer new possibilities in various fields of astronomy. The Coude Train is composed of a set of prisms, mirrors and lenses to deliver a pupil and an image in the CCL, including an Atmospheric Dispersion Compensator. The use of mainly refractive optics, and Total Internal Reflection, has the advantage of the inherent higher throughput, especially in the blue region of the spectrum. In this paper, we present the design of the Coude Train, the evolution of the concept towards the manufacturing phase, its main characteristics and performances, and detail its subsystems: optical, mechanical and control electronics and software.

ESPRESSO is an ultra-stable fiber-fed spectrograph designed to combine incoherently the light coming from up to 4 Unit Telescopes of the ESO VLT. From the Nasmyth focus of each telescope the light, through an optical path, is fed by the Coude Train subsystems to the Front End Unit placed in the Combined Coude Laboratory. The Front End is composed by one arm for each telescope and its task is to convey the incoming light, after a calibration process, into the spectrograph fibers. To perform these operations a large number of functions are foreseen, like motorized stages, lamps, digital and analog sensors that, coupled with dedicated Technical CCDs (two per arms), allow to stabilize the incoming beam up to the level needed to exploit the ESPRESSO scientific requirements. The Instrument Control Electronics goal is to properly control all the functions in the Combined Coude Laboratory and the spectrograph itself. It is fully based on a distributed PLC architecture, abandoning in this way the VME-based technology previously adopted for the ESO VLT instruments. In this paper we will describe the ESPRESSO Instrument Control Electronics architecture, focusing on the distributed layout and its interfaces with the other ESPRESSO subsystems.

The multiprism device is a crucial component of the Espresso Anamorphic pupil Slicer (APSU). At the end of the slicer, is necessary to differently fold each field to correctly illuminate the echelle. The solution is made by gluing cylindrical prisms with proper bending low angle onto a support double plate silica window. We present here the integrated robotic system conceived to reach the required tolerances in term of alignment and Integration. It consist in a tip tilt stage to select the folding angle, coupled to an x-y stage to position the elements and a z axis to perform the gluing. Keywords: Extra-solar Planet Atmospheres, High Resolution Spectroscopy, Espresso, front End

A particular example of meter class flat mirrors is the adaptive M4 Unit of E-ELT, a deformable six petals mirror of 2.4m in diameter. We studied different approaches to the calibration and certification of M4, in a trade-off between stitching and full aperture measurements. Possibilities to test the mirror with a macro-stitching concept, both in normal and grazing incidence have been considered. Approaches reported in the literature, as the Ritchey-Common or the external Fizeau, and different beam expander setups, varying the collimating mirror and the nulling system, both on-axis and off-axis, have been deeply studied to understand performances and sensitivities to fabrication errors, alignment errors and environmental effects.

We designed the interferometric test of a 300 mm flat mirror, based onto a spherical mirror and a dedicated CGH. The spherical beam of the interferometer is quasi collimated to the desired diameter by the spherical mirror, used slightly off-axis, and the CGH performs the residual wavefront correction. We performed tests on a 200 mm and 300 mm flat mirrors, and compared the results to the ones obtained by stitching, showing an accuracy well within the designed value. The possibility to calibrate the cavity by subtracting out the figure errors of the spherical mirror has also been evaluated.

This paper presents the Espresso Anamorphic pupil Slicer (APSU) implementation. For ESPRESSO that will be installed on ESO’s Very Large Telescope (VLT). In this work we will present the design and trade off for the pupil slicing system introduced in order to increase the resolving power, effectively decreasing slit width. It’s based onto simplified optical component that introduce large anamorphism while keeping low aberrations by means of cylindrical optics. We describe here the trade off between slicing through two adjacent squared doublets and two achromatic prisms. Preliminary integration and procurement is also discussed here.

ESPRESSO is the next generation European exoplanet hunter combining the efficiency of a modern echelle spectrograph with extreme radial velocity and spectroscopic precision. The instrumental radial velocity precision will be improved to reach 10 cm/s level to achieve a gain of two magnitudes with respect to its predecessor HARPS. The fiber fed non rotating instrument will be installed in the Combined Coudé Laboratory of the VLT (Very Large Telescope) which is situated in the Paranal Observatory (Chile). The main challenge in the design of the optical mounts of the instrument has been the extreme long term stability of big rectangular optical components in a seismic environment. This paper describes the requirements and the adopted solution for the opto mechanical design of the collimator mirrors dichroic lens field lens and cross dispersers of the instrument. © (2014) COPYRIGHT Society of Photo Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

ESPRESSO is a fibre-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope), and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT at the Combined Coude Laboratory (CCL), fed by four Coude Trains, which brings the light from the Nasmyth platforms of the four VLT Unit Telescopes to the CCL. ESPRESSO will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach cm/s level. Thanks to its ability of combining incoherently the light of the 4 UTs, ESPRESSO will offer new possibilities in various fields of astronomy. The Coude Train is composed of a set of prisms and lenses to deliver a pupil and an image in the CCL, including an Atmospheric Dispersion Compensator. In this paper, we present the optical design of the Coude Trains, the opto-mechanical concept, the required control, the main characteristics and expected performances.

ESPRESSO is the next European exoplanets hunter. It will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will be installed at Paranal's VLT in order to achieve two magnitudes gain with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach 10 cm/s level. We have constituted a Consortium of astronomical research institutes to fund, design and build ESPRESSO on behalf of and in collaboration with ESO, the European Southern Observatory. The project has passed the final design review in May 2013. The spectrograph will be installed at the Combined Coude Laboratory of the VLT, it will be linked to the four 8.2 meters Unit Telescopes through four optical "Coude trains" and will be operated either with a single telescope or with up to four UTs, enabling an additional 1.5 magnitude gain. Thanks to its characteristics and ability of combining incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in many fields of astronomy. Our main scientific objectives are, however, the search and characterization of rocky exoplanets in the habitable zone of quiet, near-by G to M-dwarfs, and the analysis of the variability of fundamental physical constants. In this paper, we will present the scientific objectives, the capabilities of ESPRESSO, the technical solutions for the system and its subsystems, enlightening the main differences between ESPRESSO and its predecessors. The project aspects of this facility are also described, from the consortium and partnership structure to the planning phases and milestones.

Next-generation infrared astronomical instrumentation for ground-based and space telescopes could be based on MOEMS programmable slit masks for multi-object spectroscopy (MOS). This astronomical technique is used extensively to investigate the formation and evolution of galaxies. We propose to develop a 2048x1080 DMD-based MOS instrument to be mounted on the Galileo telescope and called BATMAN. A two-arm instrument has been designed for providing in parallel imaging and spectroscopic capabilities. The two arms with F/4 on the DMD are mounted on a common bench, and an upper bench supports the detectors thanks to two independent hexapods. Very good optical quality on the DMD and the detectors will be reached. ROBIN, a BATMAN demonstrator, has been designed, realized and integrated. It permits to determine the instrument integration procedure, including optics and mechanics integration, alignment procedure and optical quality. First images have been obtained and measured. A DMD pattern manager has been developed in order to generate any slit mask according to the list of objects to be observed; spectra have been generated and measured. Observation strategies will be studied and demonstrated for the scientific optimization strategy over the whole FOV. BATMAN on the sky is of prime importance for characterizing the actual performance of this new family of MOS instruments, as well as investigating the operational procedures on astronomical objects. This instrument will be placed on the Telescopio Nazionale Galileo at the beginning of next year, in 2014.

This paper presents the Espresso Exposure Meter (EM) implementation. ESPRESSO,1-3 the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, will be installed on ESOs Very Large Telescope (VLT). The light coming from the Telescope through a Coud Focus4 of all the Four Telescope Units (UTs) will be collected by the Front End Unit that provides Field and Pupil stabilisation and injects the beams into the Spectrograph fibers.5 An advanced Exposure Meter system will be used to correct Radial Velocity (RV) obtained from the scientific spectrum for the Earth relative motion. In this work we will present the perfor mance of an innovative concept for the Exposure Meter system based on a Charge Coupled Device (CCD) with a chromatic approach for the calculation of the Mean Time of Exposure (MTE). The MTE is a crucial quantity used for the correction of RV for the Earth relative motion during the exposure. In particular, splitting the light in different chromatic channels on the CCD, we will probe for potential chromatic effects on the calculation of the MTE in each channel and how they could be used in order to perform the correction of RV. The paper is accompanied by a fully described numerical analysis that keeps into view a key performance evaluation for different stellar spectral types (B to M spectral main sequence classes).

This paper is a study on the numerical modeling and the accordance between model and experiment of the behavior of Shape Memory Alloys (SMA) used as functional devices for application in Instrumentations for Astronomy. Some NiTi alloy samples was characterized using different experimental techniques, with the purpose of obtaining the material parameters, necessary to evaluate the correspondence between the simulation and the experimental behavior of the materials. The sensibility of the computational model to the variation of this parameters for the materials was investigated as well. Opto-mechanical mounting with pseudoelastic kinematic behavior and damping of launch loads onto optical elements are feasible applications that are investigated in this paper. The practical realization of a scaled down prototype is described. The device was thought for ground-based applications and made up of four small flexures that support an optical component and was designed and modeled in order to be able to evaluate the mechanical effects of different materials. The results of numerical modeling was compared to the data obtained from the prototype. We obtained a first evaluation of the development, selection and processing of NiTi-based supports for optomechanical applications and verified the performances of a complete system as a respect to an analogous system made up using traditional materials like steels. © 2013 SPIE.

16th Conference of Novel Optical Systems Design and Optimization, August 26-28, 2013, San Diego, CA, USA, Series: Proceedings of SPIE

This paper wants to address the opto-mechanical stability of the Codex instrument pending onto vibration environment. CODEX is a study for an high resolution spectrograph for the European ELT. In particular the aim of the work is a preliminary verification of the instrument performances if mounted at the E-ELT Folded Nasmith location. Hence Dynamic environment of the Coude and the folded Nasmith locations were alternatively applied to the optical layout to verify the image performances in terms of image displacements and FWHM deformations. In addition damping strategies has been verified for the improvement of the performances.

ESPRESSO, the VLT rocky exoplanets hunter, will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will be installed at Paranal on ESO's VLT in order to achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach 10 cm/s level. We have constituted a Consortium of astronomical research institutes to fund, design and build ESPRESSO on behalf of and in collaboration with ESO, the European Southern Observatory. The project has passed the preliminary design review in November 2011. The spectrograph will be installed at the so-called "Combined Coude Laboratory" of the VLT, it will be linked to the four 8.2 meters Unit Telescopes (UT) through four optical "Coude trains" and will be operated either with a single telescope or with up to four UTs. In exchange of the major financial and human effort the building Consortium will be awarded with guaranteed observing time (GTO), which will be invested in a common scientific program. Thanks to its characteristics and the ability of combining incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in many fields of astronomy. Our main scientific objectives are, however, the search and characterization of rocky exoplanets in the habitable zone of quiet, near-by G to M-dwarfs, and the analysis of the variability of fundamental physical constants. In this paper, we present the ambitious scientific objectives, the capabilities of ESPRESSO, the technical solutions for the system and its subsystems, enlightening the main differences between ESPRESSO and its predecessors. The project aspects of this facility are also described, from the consortium and partnership structure to the planning phases and milestones.

Multi-Object Spectrographs (MOS) are the major instruments for studying primary galaxies and remote and faint objects. Current object selection systems are limited and/or difficult to implement in next generation MOS for space and groundbased telescopes. A promising solution is the use of MOEMS devices such as micromirror arrays which allow the remote control of the multi-slit configuration in real time. We are developing a Digital Micromirror Device (DMD) - based spectrograph demonstrator called BATMAN. We want to access the largest FOV with the highest contrast. The selected component is a DMD chip from Texas Instruments in 2048 x 1080 mirrors format, with a pitch of 13.68μm. Our optical design is an all-reflective spectrograph design with F/4 on the DMD component. This demonstrator permits the study of key parameters such as throughput, contrast and ability to remove unwanted sources in the FOV (background, spoiler sources), PSF effect, new observational modes. This study will be conducted in the visible with possible extension in the IR. A breadboard on an optical bench, ROBIN, has been developed for a preliminary determination of these parameters. The demonstrator on the sky is then of prime importance for characterizing the actual performance of this new family of instruments, as well as investigating the operational procedures on astronomical objects. BATMAN will be placed on the Nasmyth focus of Telescopio Nazionale Galileo (TNG) during next year.

This paper presents the Espresso Front End Guiding Algorithm. ESPRESSO, the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, will be installed on ESO's Very Large Telescope (VLT). The Front End (FE) is the subsystem that collects the light coming from the Coude Trains of all the Four Telescope Units (UTs), provides Field and Pupil stabilization via piezoelectric tip tilt devices and inject the beams into the Spectrograph fibers. The field and pupil guiding is obtained through a re-imaging system that elaborates the halo of the light out of the Injection Fiber and a telescope pupil beacon. The first guiding algorithm that we evaluated splits the FP in four areas and computes the sum of the photon counting of each pixel in that area. The unbalancing of the photon sums will give the centroid misalignment information that will be handled by the Instrument Control Software (ICS). Different algorithms and controllers architectures have been evaluated and implemented in order to select a strategy that enables the FE to guide up to 20 apparent magnitude in V band.

ESPRESSO is a fiber-fed cross-dispersed echelle spectrograph which can be operated with one or up to 4 UT (Unit Telescope) of ESO's Very Large Telescope (VLT). It will be located in the Combined-Coude Laboratory (CCL) of the VLT and it will be the first permanent instrument using a 16-m equivalent telescope. The ESPRESSO control software and electronics are in charge of the control of all instrument subsystems: the four Coude Trains (one for each UT), the front-end and the fiber-fed spectrograph itself contained within a vacuum vessel. The spectrograph is installed inside a series of thermal enclosures following an onion-shell principle with increasing temperature stability from outside to inside. The proposed electronics architecture will use the OPC Unified Architecture (OPC UA) as a standard layer to communicate with PLCs (Programmable Logical Controller), replacing the old Instrument Local Control Units (LCUs) for ESO instruments based on VME technology. The instrument control software will be based on the VLT Control Software package and will use the IC0 Field Bus extension for the control of the instrument hardware. In this paper we present the ESPRESSO software architectural design proposed at the Preliminary Design Review as well as the control electronics architecture.

This paper presents the Espresso Front End mechanical and optical conguration. ESPRESSO, Echelle SPectro-graph for Rocky Exoplanets and Stable Spectroscopic Observations, will combine the efficiency of modern echelle spectrograph design with extreme radial-velocity precision. It will be installed on ESO's VLT and it is expected to achieve a gain of two magnitudes with respect to its predecessor HARPS. The instrumental radial-velocity precision will also be improved to reach cm/s level. The Front End is a modular subsystem that collects the light coming from the Coude Trains of all the Four Telescope Units (UT), provides Field and Pupil stabilization via piezoelectric tip tilt devices and inject the beam into the Spectrograph fiber. The Front End will also inject the calibration light coming from the calibration unit. There will be four Front End modules, one per UT. A rotary Stage will provide the toggling between different observation mode: Single UT Ultra High resolution (SUT-UHR), Single UT High resolution (SUT-HR) and multiple UTS Mid Rsolution (MUT-MR). The field and pupil guiding is obtained through a reimaging system that elaborates the halo of the light out of the Injection Fiber and a telescope pupil beacon. A dedicated guiding algorithm has been studied in order to provide proper image stability even with faint objects (mv=20).

This paper want to show an innovative amateur oriented telescope with an unconventional alt-alt conguration. The goal is to make a telescope with good optical quality reducing production costs by adopting a gimbal based mounting to develop an alt-alt conguration suitable for a telescope. Reduce costs while preserving the optical quality is a necessary condition to allow small groups of amateur astronomers, schools and cultural clubs, with reduced economic resources, to acquire an astronomical instrument that encourages learning and advancing astrophysical knowledge. This unconventional mechanism for the realization of a telescope alt-alt provides signicant advantages. The traditional rotary motors coupled with expensive precision bearings are replaced with two simple linear actuators coupled to a properly preloaded gimbal joint and the cell becomes the primary structure of the telescope. A second advantage would be secured by mechanical simplicity evident in the easy portability of the instrument. The frame alt-alt has some limitations on the horizon pointing but does not show the zenith blind spot of the alt-az mount. A dedicated alt-alt pointing and tracking model is under development to be compatible with commercial telescope softwares and with the proposed new mounting.

ESPRESSO is a fiber-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope), and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT at the Combined Coude Laboratory (CCL), fed by four Coude Trains, which brings the light from the Nasmyth platforms of the four VLT Unit Telescopes to the CCL. A previous trade-off analysis, considering the use of mirrors, prisms, lenses or fibers and several possible combinations of them, pointed towards a Full Optics solution, using only conventional optics to launch the light from the telescope into the front-end unit. In this case, the system is composed of a set of prisms and lenses to deliver a pupil and an image in the CCL, including an Atmospheric Dispersion Compensator. In this paper, we present the optical design of the Coude Trains, the opto-mechanical concept, the main characteristics and expected performances.

Volume phase holographic gratings (VPHGs) are dispersing elements widely used in astronomical instrumentation thanks to some unique features (for example, the peak efficiency can reach 95%). The introduction of a slant angle to the fringes allow an increased versatility of these elements. The efficiencies of some samples produced by Kaiser Optical Systems Inc. are reported and discussed. Moreover, some cases of interest in the astronomical field are reported.

Innovative optical interferometry test setups and control software techniques have been proposed for the E-ELT M4 adaptive optics mirror. The system is composed of three sub-systems: a CGH-based optical test tower, delivering a 1.5-m collimated beam, for fast simultaneous acquisition of large areas; a stitching interferometer, to calibrate at higher spatial frequencies, on smaller areas; and an optical piston sensor to remove differential piston and tilt between adjacent mirror segments., Adaptive Optics Systems III, July 1-6, 2012, Amsterdam, Netherlands, Series: Proceedings of SPIE

This paper wants to illustrate possible applications of Shape Memory Alloy (SMA) as functional devices for space and ground based application in Instrumentations for Astronomy. Thermal activated Shape Memory Alloys are materials able to recover their original shape, after an external deformation, if heated above a characteristic temperature. If the recovery of the shape is completely or partially prevented by the presence of constraints, the material can generate recovery stress. Thanks to this feature, these materials can be positively exploited in Smart Structures if properly embedded into host materials. Some technological processes developed for an ecient use of SMA-based actuators embedded in smart structures tailored to astronomical instrumentation will be presented here. Some possible modeling approaches of the actuators behavior will be addressed taking into account trade- offs between detailed analysis and overall performance prediction as a function of the computational time. The Material characterization procedure adopted for the constitutive laws implementation will be described as well. Deformable composite mirrors,1 opto-mechanical mounting with superelastic kinematic behavior and damping of launch loads onto optical element2 are feasible applications that will be deeply investigated in this paper.

This paper presents the GWA and the Compensating mechanism of the Near Infrared SpectroPhotometer (NISP) instrument of the ESA Euclid mission. The NIS instrument should perform an exposure sequence in the wave­ length range [0.9 - 2.0Jum with different exposures of the same field of views with different passband grisms with two orthogonal dispersion directions and two wavelength range. These functionalities will be achieved by a mechanism supporting the optical elements: the Grism Wheel Assembly (GWA). The required positioning repeatability is in the order of few arcsec to keep the spectra aligned with the detector pixel columns/rows. The GWA will be assembled to the NISP Optomechanical Assembly (NIOMA) with an operating temperature of 140K. A further mechanism is necessary to compensate the torque perturbances induced by the two large wheels. It is based onto a stepper motor that will drive a flywheel.

The Near Infrared Spectro-Photometer (NISP) on board the Euclid ESA mission will be developed and tested at various levels of integration using various test equipment which shall be designed and procured through a collaborative and coordinated effort. In this paper we describe the Electrical Ground Support Equipment (EGSE) which shall be required to support the assembly, integration, verification and testing (AIV/AIT) and calibration activities at instrument level before delivery to ESA, and at satellite level, when the NISP instrument is mounted on the spacecraft. We present the EGSE conceptual design as defined in order to be compliant with the AIV/AIT and calibration requirements. The proposed concept is aimed at maximizing the re-use in the EGSE configuration of the Test Equipment developed for subsystem level activities, as well as, at allowing a smooth transition from instrument level to satellite level, and, possibly, at Ground Segment level. This paper mainly reports the technical status at the end of the Definition phase and it is presented on behalf of the Euclid Consortium.

In this paper we describe the thermal architecture of the Near Infrared Spectro-Photometer (NISP) on board the Euclid ESA mission. The instrument thermal design is based on the combination of two passive radiators coupled to cold space that, exploiting the beneficial conditions of the L2 thermal environment, provide the temperature references for the main sub-systems. One radiator serves as a 135K heat sink for the opto-mechanical structure and for the front-end cold electronics, while working as an interception stage for the conductive parasitic heat leaks through struts and harness. The second, colder, radiator provides a 95K reference for the instrument detectors. The thermal configuration has to ensure the units optimal operating temperature needed to maximize instrument performance, adopting solutions consistent with the mechanical specifications. At the same time the design has to be compliant with the stringent requirements on thermal stability of the optical and detector units. The periodical perturbation of filter and grism wheel mechanisms together with orbital variations and active loads instabilities make the temperature control one of the most critical issues of the whole design. We report here the general thermal architecture at the end of the Definition Phase, together with the first analysis results and preliminary performance predictions in terms of steady state and transient behavior. This paper is presented on behalf of the Euclid Consortium.

NISP is the near IR spectrophotometer instrument part of the Cosmic Vision Euclid mission. In this paper we describe an end-to-end simulation scheme developed in the framework of the NISP design study to cover the expected focal-plane on-board pre-processing operations. Non-destructive detector readouts are simulated for a number of different readout strategies, taking into account scientific and calibration observations; resulting frames are passed through a series of steps emulating the foreseen on-board pipeline, then compressed to give the final result. In order to verify final frame quality and resulting computational and memory load, we tested this architecture on a number of hardware platforms similar to those possible for the final NISP computing unit. Here we give the results of the latest tests. This paper mainly reports the technical status at the end of the Definition Phase and it is presented on behalf of the Euclid Consortium.