Search

We present in this report the design of the atmospheric dispersion compensator for the adaptive optics system of DAG, the new 4 m Turkish telescope. An Amici configuration has been chosen, made of a pair of doublets prisms, located on both side of the tip-tilt mirror of the system’s pyramid wavefront sensor. Our design methodology, using a Python controlled ZEMAX model, is described, with our results, as well as the design of a triplet lens to compensate for the remaining pupil nutation.

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

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)

We present the design of the Adaptive Optics System for the new Turkish 4-m telescope (DAG). The AO will use a pyramid WFS, with a double prism and a no noise EM-CCD camera to allow for oversampling of the pupil images and a relaxation of the prism manufacturing tolerances. In order to use the high modal resolution of the P-WFS allowed by the adjustment of the modulation angle, we implement a high order deformable mirror with 468 actuators, which will permit to use the system in extreme AO correction mode. The P-WFS optical design has been largely inspired by NFIRAOS truth WFS. The number of optical surfaces has been reduced to the bare minimum. An atmospheric dispersion compensator is introduced around the tip-tilt modulation mirror. In this proceeding, we present the detail of the optical design steps for all the components of the system. SPIE Publisher's Version WOS:000850783300080

Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave; Virtual, Online; United States; 14 December 2020 through 22 December 2020; Code 166572.--Proceedings of SPIE - The International Society for Optical Engineering Volume 11443, 2020, Article number 1144379.--Full list of authors: Da Deppo, Vania; Pernechele, Claudio; Jones, Geraint H.; Brydon, George; Zuppella, Paola; Chioetto, Paolo; Nordera, Simone; Slemer, Alessandra; Crescenzio, Giuseppe; Piersanti, Emanuele; Spanò, Paolo; Bucciol, Gino; Consolaro, Luca; Lara, Luisa; Slavinskis, Andris, EnVisS (Entire Visible Sky) is an all-sky camera specifically designed to fly on the space mission Comet Interceptor. This mission has been selected in June 2019 as the first European Space Agency (ESA) Fast mission, a modest size mission with fast implementation. Comet Interceptor aims to study a dynamically new comet, or interstellar object, and its launch is scheduled in 2029 as a companion to the ARIEL mission. The mission study phase, called Phase 0, has been completed in December 2019, and then the Phase A study had started. Phase A will last for about two years until mission adoption expected in June 2022. The Comet Interceptor mission is conceived to be composed of three spacecraft: spacecraft A devoted to remote sensing science, and the other two, spacecraft B1 and B2, dedicated to a fly-by with the comet. EnVisS will be mounted on spacecraft B2, which is foreseen to be spin-stabilized. The camera is developed with the scientific task to image, in push-frame mode, the full comet coma in different colors. A set of ad-hoc selected broadband filters and polarizers in the visible range will be used to study the full scale distribution of the coma gas and dust species. The camera configuration is a fish-eye lens system with a FoV of about 180°x45°. This paper will describe the preliminary EnVisS optical head design and analysis carried out during the Phase 0 study of the mission. © COPYRIGHT SPIE., This activity has been conducted and funded through an Agenzia Spaziale Italiana (ASI) contract to the Istituto Nazionale di Astrofisica (INAF) n. 2020-4-HH.0.

We present a multi-conjugate adaptive optics (MCAO) system simulator bench, HeNOS (Herzberg NFIRAOS Optical Simulator). HeNOS is developed to validate the performance of the MCAO system for the Thirty Meter Telescope, as well as to demonstrate techniques critical for future AO developments. In this paper, we focus on describing the derivations of parameters that scale the 30-m telescope AO system down to a bench experiment and explain how these parameters are practically implemented on an optical bench. While referring other papers for details of AO technique developments using HeNOS, we introduce the functionality of HeNOS, in particular, three different single-conjugate AO modes that HeNOS currently offers: a laser guide star AO with a Shack-Hartmann wavefront sensor, a natural guide star AO with a pyramid wavefront sensor, and a laser guide star AO with a sodium spot elongation on the Shack-Hartmann corrected by a truth wavefront sensing on a natural guide star. Laser tomography AO and ultimate MCAO are being prepared to be implemented in the near future.

International audience

The Enhanced Resolution Imager and Spectrograph (ERIS) is a new-generation instrument for the Cassegrain focus of the ESO UT4/VLT, aimed at performing AO-assisted imaging and medium resolution spectroscopy in the 1-5 micron wavelength range. ERIS consists of the 1-5 micron imaging camera NIX, the 1-2.5 micron integral field spectrograph SPIFFIER (a modified version of SPIFFI, currently operating on SINFONI), the AO module and the internal Calibration Unit (ERIS CU). The purpose of this unit is to provide facilities to calibrate the scientific instruments in the 1-2.5 micron and to perform troubleshooting and periodic maintenance tests of the AO module (e.g. NGS and LGS WFS internal calibrations and functionalities, ERIS differential flexures) in the 0.5 - 1 μm range. The ERIS CU must therefore be designed in order to provide, over the full 0.5 - 2.5 μm range, the following capabilities: 1) illumination of both the telescope focal plane and the telescope pupil with a high-degree of uniformity; 2) artificial point-like and extended sources onto the telescope focal plane, with high accuracy in both positioning and FWHM; 3) wavelength calibration; 4) high stability of these characteristics. In this paper the design of the ERIS CU, and the solutions adopted to fulfill all these requirements, is described. The ERIS CU construction is foreseen to start at the end of 2016.

In this paper we present numerical simulations and an initial design for a visible MCAO system for the VLT-UT4 telescope. The proposed concept takes great advantage of the existing HW developed for the Adaptive Optics Facility (AOF) at the VLT-UT4, in particular the 4x20W Toptica lasers and the adaptive secondary mirror with 1170 actuators. The mentioned units makes the VLT-AOF a unique facility to develop a second generation AO system aiming to provide corrected FoV at short wavelength. In particular the flux provided by the four lasers steerable on sky and the high density of actuators (20cm equivalent on M1) provides the temporal bandwidth and the spatial sampling to push the correction down to the visible wavelengths. In addition to this the request of a reasonable size corrected FoV with uniform performance calls for an MCAO system. For such reason here we propose to complement the AOF with post-focal DMs that together with the VLT DSM can provide a corrected FoV of roughly 20/30 arcsec diameter size. An additional challenge for the system is the provided a large sky coverage. Such condition comes from the efficiency of LO wavefront sensors that use field NGS. The presented simulations give some first results for (a) the achieved performance at visible wavelength 0.4-0.9 um as a function of DMs and tip tilt NGSs characteristics (b) the achieved system sky coverage after. Pushing performance toward visible wavelengths calls for embedded and efficient post-processing methods. Being able to capture short-exposure science images (with the trade-off on noise and overheads), would allow retrieving the ultimate performance by compensating the residual turbulence aberrations left over by the AO system. Considerations about advanced analysis tools that may potentially relax the system constraints are discussed. Finally the paper presents a conceptual arrangement for the opto-mechanics of the considered AO module including the additional DMs and wavefront sensors.

ERIS is the new AO instrument for VLT-UT4 led by a Consortium of Max-Planck Institut fuer Extraterrestrische Physik, UK-ATC, ETH-Zurich, ESO and INAF. The ERIS AO system provides NGS mode to deliver high contrast correction and LGS mode to extend high Strehl performance to large sky coverage. The AO module includes NGS and LGS wavefront sensors and, with VLT-AOF Deformable Secondary Mirror and Laser Facility, will provide AO correction to the high resolution imager NIX (1-5um) and the IFU spectrograph SPIFFIER (1-2.5um). In this paper we present the preliminary design of the ERIS AO system and the estimated correction performance., Comment: 11 pages, 11 figures, 1 table. SPIE conference Astronomical Telescopes and Instrumentation, 26 June - 01 July 2016, Edinburgh, Scotland, United Kingdom

8s stands for Optical Test TOwer Simulator (with 8 read as in italian 'otto'): it is a simulation tool for the optical calibration of the E-ELT deformable mirror M4 on its test facility. It has been developed to identify possible criticalities in the procedure, evaluate the solutions and estimate the sensitivity to environmental noise. The simulation system is composed by the finite elements model of the tower, the analytic influence functions of the actuators, the ray tracing propagation of the laser beam through the optical surfaces. The tool delivers simulated phasemaps of M4, associated with the current system status: actuator commands, optics alignment and position, beam vignetting, bench temperature and vibrations. It is possible to simulate a single step of the optical test of M4 by changing the system parameters according to a calibration procedure and collect the associated phasemap for performance evaluation. In this paper we will describe the simulation package and outline the proposed calibration procedure of M4.

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.

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.

At NRC Herzberg - Astronomy we are developing a closed-loop multi-conjugate adaptive optics bench to simulate a scaled-down version of NFIRAOS, the first light MCAO system on the Thirty Meter Telescope. The current bench consists of four laser guide stars, an evenly spaced array of natural guide stars, two magnetic deformable mirrors, a Shack-Hartmann wavefront sensor and a science camera at the focal plane for the evaluation of the performance and the tip-tilt measurements. Three phase screens conjugated at different altitudes simulate the atmospheric perturbation over the telescope. We can recreate the spot elongation on the SHWFS by defocusing the ground DM and at the same time modulating the intensity of the LGS spots in order to simulate the timevarying density profile of the sodium layer. The goals of this experiment are to compare the experimental performance on the bench with the predicted results of NFIRAOS models and to test the robustness of the tomographic reconstruction under conditions including the use of faint guide stars, non-uniform density profiles of the sodium layer and known non-common path aberrations. In this paper we present an update on the status of the bench and some first results., Adaptive Optics Systems IV, June 22-27, 2014, Series: Proceedings of SPIE; no. 9148

During 2013, a new visible camera has been finally installed and tested at the 60cm, robotic REM telescope in the la Silla Observatory. REM is an Italian, fast-reacting telescope initially designed and built for the immediate response to GRB automatic alerts, but since the first light in 2003 its usage has been covering a wider range of astronomical interests. While the IR camera REMIR was reaching the expected limiting magnitudes, the original ROSS visible camera suffered, since the beginning, of a rather poor performance. We set therefore to implement a newer optical camera, leading to the design, tests and integration of ROS2, a dichroic-based four channels imaging camera. The four Sloan-like pass bands are imaged, at the same time, in four quadrants of the CCD, an Andor multilevel Peltier detector. The tests during the science commissioning show an impressive improvement in the limiting magnitudes, reaching two magnitudes fainter than ROSS. Here we show the concept, the tests and the user level product we are now offering at REM.

NFIRAOS, the Thirty Meter Telescope's first adaptive optics system is an order 60x60 Multi-Conjugate AO system with two deformable mirrors. Although most observing will use 6 laser guide stars, it also has an NGS-only mode. Uniquely, NFIRAOS is cooled to -30 °C to reduce thermal background. NFIRAOS delivers a 2-arcminute beam to three client instruments, and relies on up to three IR WFSs in each instrument. We present recent work including: robust automated acquisition on these IR WFSs; trade-off studies for a common-size of deformable mirror; real-time computing architectures; simplified designs for high-order NGS-mode wavefront sensing; modest upgrade concepts for high-contrast imaging., Adaptive Optics Systems IV, June 22-27, 2014, Series: Proceedings of SPIE; no. 9148

10 pages dans la version publiée sur papier: 20 pages en version "online" avec les tables complètes.; International audience; We present relative astrometric measurements of visual binaries, made in 2011 with the Pupil Interferometry Speckle camera and COronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera Astronomical Observatory in Merate (Italy). Our observing list contains orbital couples as well as binaries whose motion is still uncertain. We obtained new measurements of 469 objects, with angular separations in the range 0.14-8.1 arcsec, and an average accuracy of 0.02 arcsec. The mean error on the position angles is 0 .^{circ}7. Most of the position angles were determined without the usual 180° ambiguity with the application of triple-correlation techniques and/or by inspection of the long integration files. Thanks to a new low-magnification option included in PISCO, we have been able to observe fainter stars than previously. The limiting magnitude of our instrumentation on the Zeiss telescope is now close to mV = 10-12, which permits the observation of some red dwarfs. Finally, we present new revised orbits for ADS 8739, 9182 Aa,Ab, 9626 Ba,Bb, 12880 and 14412, partly derived from those observations. The corresponding estimated values for the masses of those systems are compatible with the spectral types.

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.

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 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.

We describe the optical test of a large flat based on a spherical mirror and a dedicated CGH. The spherical mirror, which can be accurately manufactured and tested in absolute way, allows to obtain a quasi collimated light beam, and the hologram performs the residual wavefront correction. Alignment tools for the spherical mirror and the hologram itself are encoded in the CGH. Sensitivity to fabrication errors and alignment has been evaluated. Tests to verify the effectiveness of our approach are now under execution. © 2012 SPIE., Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation II, 1 July 2012 through 6 July 2012, Amsterdam, Series: Proceedings of SPIE

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

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.

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 ground-based 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. We want to access the largest FOV with the highest contrast. The selected component is a DMD chip from Texas Instruments in 2048 × 1080 mirrors format, with a pitch of 13.68μm. Such component has been also studied by our team in early phase EUCLID-NIS study. Our optical design is an all-reflective spectrograph design with F/4 on the DMD component, including two arms, one spectroscopic channel and one imaging channel, thanks to the two stable positions of DMD micromirrors. This demonstrator permits the study of key parameters such as throughput, contrast and ability to remove background and spoiler sources, PSF effect. This study will be conducted in the visible with possible extension in the IR. The breadboard has been designed and is under realization before integration on a bench simulating an astronomical FOV. The demonstrator is of prime importance for characterizing the actual performance of this new family of instruments, as well as investigating the operational procedures on astronomical objects. If this demonstrator is successful, next step will be a demonstrator instrument placed on the Telescopio Nazionale Galileo.

The European ESA EUCLID dark energy, dark matter mission is presented with respect to the near instrument optics. We present the nominal optics approach as well as the tolerancing concept and the results of this tolerancing. through this we are able to show that the merged near infrared spectrometer and photometer NISP can be built with high image quality in a sophisticated but well performing approach. Furthermore a ghost analysis for NISP is presented, showing that reflective ghost have been successfully suppressed during the optimization process.

OCTOCAM is a multi-channel imager and spectrograph that has been proposed for the 10.4m GTC telescope. It will use dichroics to split the incoming light to produce simultaneous observations in 8 different bands, ranging from the ultraviolet to the near-infrared. The imaging mode will have a field of view of 2' x 2' in u, g, r, i, z, J, H and Ks bands, whereas the long-slit spectroscopic mode will cover the complete range from 4,000 to 23,000 {\AA} with a resolution of 700 - 1,700 (depending on the arm and slit width). An additional mode, using an image slicer, will deliver a spectral resolution of over 3,000. As a further feature, it will use state of the art detectors to reach high readout speeds of the order of tens of milliseconds. In this way, OCTOCAM will be occupying a region of the time resolution - spectral resolution - spectral coverage diagram that is not covered by a single instrument in any other observatory, with an exceptional sensitivity., Comment: 11 pages, 10 figures, SPIE 2010 Astronomical Instrumentation

OPTIMOS-EVE is a fiber-fed, high-multiplex, high-efficiency, large spectral coverage spectrograph for EELT covering visible and near-infrared simultaneously. More than 200 seeing-limited objects will be observed at the same time over the full 7 arcmin field of view of the telescope, feeding the spectrograph, asking for very large multiplexing at the spectrograph side. The spectrograph consists of two identical units. Each unit will have two optimized channels to observe both visible and near-infrared wavelengths at the same time, covering from 0.37 to 1.7 micron. To maximize the scientific return, a large simultaneous spectral coverage per exposure was required, up to 1/3 of the central wavelength. Moreover, different spectral resolution modes, spanning from 5'000 to 30'000, were defined to match very different sky targets. Many different optical solutions were generated during the initial study phase in order to select that one that will maximize performances within given constraints (mass, space, cost). Here we present the results of this study, with special attention to the baseline design. Efforts were done to keep size of the optical components well within present state-of-the-art technologies. For example, large glass blank sizes were limited to ~35 cm maximum diameter. VPH gratings were selected as dispersers, to improve efficiency, following their superblaze curve. This led to scanning gratings and cameras. Optical design will be described, together with expected performances.

The challenge of building extremely large telescope pushes forward the parallel ability to measure and test optical components of large sizes. Here we present the optical bench setup for the Demonstration Prototype (DP) of the voice coil controlled adaptive mirror M4AU of the E-ELT. A set of three devices has been chosen and used for the tests, whose results are also shown. The performance demonstrated that this is a viable and trusted technology and the DP tests were highly representative of the whole procedure that could be applied to the real, full size unit.

ESPRESSO, a very high-resolution, high-efficiency, ultra-high stability, fiber-fed, cross-dispersed echelle spectrograph located in the Combined-Coude focus of the VLT, has been designed to detect exo-planets with unprecedented radial velocity accuracies of 10 cm/sec over 20 years period. To increase spectral resolution, an innovative pupil slicing technique has been adopted, based onto free-form optics. Anamorphism has been added to increase resolution while keeping the physical size of the echelle grating within reasonable limits. Anamorphic VPH grisms will help to decrease detector size, while maximizing efficiency and inter-order separation. Here we present a summary of the optical design of the spectrograph and of expected performances.

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 ground-based 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. 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. Such component has been also studied by our team for application in EUCLID-NIS. 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, spectrum stability on the detector. This study will be conducted in the visible with possible extension in the IR. A breadboard on an optical bench 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. This demonstrator will be studied in order to be placed on the Telescopio Nazionale Galileo during next year.

Aspherical optics are widely used in modern optical telescopes and instrumentation because of their ability to reduce aberrations with a simple optical system. Testing their optical quality through null interferometry is not trivial as reference optics are not available. Computer-Generated Holograms (CGHs) are efficient devices that allow to generate a well-defined optical wavefront. We developed rewritable Computer Generated Holograms for the interferometric test of aspheres based on photochromic layers. These photochromic holograms are cost-effective and the method of production does not need any post exposure process.

The design of astronomical instrument is growing in dimension and complexity, following the new requirements imposed by ELT class telescopes. The availability of new structural material like composite ones is asking for more robust and reliable designing numerical tools. This paper wants to show a possible integrated design framework. The procedure starts from the developing of a raw structure consisting in an assembly of plates and beams directly from the optical design. The basic Finite Element Model is then prepared joining together plate and beam elements for the structure and mass and semi-rigid element for the the opto-mechanical subsystems. The technique developed is based onto Matlab® commands and run the FEA, extrapolate the optical displacements, implement them into the optical design and evaluates the image quality in terms of displacement and spot size. Thanks to a simplified procedure the routine is able to derive the full field of displacements from a reduced sequence of three different load sets. The automatic optimization routine modifies the properties of plates and beams considering also different materials and, in case of composites different lamination sequences. The algorithm is oriented to find the best compromise in terms of overall weights w.r.t. eigen-frequencies, image stability and quality.

ESPRESSO, the Echelle SPectrograph 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 in order to achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radialvelocity precision will be improved to reach cm/s level. Thanks to its characteristics and the ability of combining incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in various fields of astronomy. The main scientific objectives will be the search and characterization of rocky exoplanets in the habitable zone of quiet, nearby G to M-dwarfs, and the analysis of the variability of fundamental physical constants. We will present the ambitious scientific objectives, the capabilities of ESPRESSO, and the technical solutions of this challenging project.

We present our design of the E-ELT M4 Adaptive Unit based on voice-coil driven deformable mirror technology. This technology was developed by INAF-Arcetri, Microgate and ADS team in the past 15 years and it has been adopted by a number of large ground based telescopes as the MMT, LBT, Magellan and lastly the VLT in the frame of the Adaptive Telescope Facility project. Our design is based on contactless force actuators made by permanent magnets glued on the back of the deformable mirror and coils mounted on a stiff reference structure. We use capacitive sensors to close a position loop co-located with each actuator. Dedicated high performance parallel processors are used to implement the local de-centralized control at actuator level and a centralized feed-forward computation of all the actuators forces. This allowed achieving in our previous systems dynamic performances well in line with the requirements of the M4 Adaptive Unit (M4AU) case. The actuator density of our design is in the order of 30-mm spacing for a figure of about 6000 actuators on the M4AU and it allows fulfilling the fitting error and corrections requirements of the E-ELT high order DM. Moreover, our contact-less technology makes the Deformable Mirror tolerant to up 5% actuators failures without spoiling system capability to reach its specified performances, besides allowing large mechanical tolerances between the reference structure and the deformable mirror. Finally, we present the Demonstration Prototype we are building in the frame of the M4AU Phase B study to measure the optical dynamical performances predicted by our design. Such a prototype will be fully representative of the M4AU features, in particular it will address the controllability of two adjacent segments of the 2-mm thick mirror and implement the actuators "brick" modular concept that has been adopted to dramatically improve the maintainability of the final unit.

During the last years, a number of telescopes and instruments have been dedicated to the follow-up of GRBs: recent studies of the prompt emission (see for instance GRB080319B) and of their afterglows, evidenced a series of phenomena that do not fit very well within the standard fireball model. In those cases, optical observations were fundamental to distinguish among different emission mechanisms and models. In particular, simultaneous observation in various optical filters became essential to understand the physics, and we discovered the need to have a detailed high time resolution follow up. Finally, recent observations of the polarization in GRB 090102 clearly indicate the presence of an ordered magnetic field favoring the electromagnetic outflows models. This is, however, only one case and, in order to detail properly the model, we need a bit of statistics. But, after the Swift launch, the average observed intensity of GRB afterglows showed to be lower than thought before. Robotic telescopes, as demonstrated by REM, ROTSE, TAROT, etc. (but see also the GROND set up) is clearly the winning strategy. Indeed, as we will also briefly discuss later on, the understanding of the prompt emission mechanism depends on the observations covering the first few hundreds seconds since the beginning of the event with high temporal resolution. To tackle these problems and track down a realistic model, we started the conceptual design and phase A study of a 4 meter class, fast-pointing telescope (40 sec on target), equipped with multichannel imagers, from Visible to Near Infrared (Codevisir/Pathos). In the study we explored all the different parts of the project, from the telescope to the instrumental suite to data managing and analysis, to the dome and site issue. Contacts with industry have been fruitful in understanding the actual feasibility of building such a complex machine and no show stoppers have been identified, even if some critical points should be better addressed in the Phase B study. In this paper, we present the main results of the feasibility study we performed.

14 páginas, 17 figuras, 2 tablas.-- This is an open access article distributed under the Creative Commons Attribution License.-- et al., During the last years, a number of telescopes have been dedicated to the followup of the GRBs. But after the Swift launch, the average observed intensity of the GRBs showed to be lower than thought before. Our experience with the robotic 60 cm REM telescope confirmed this evidence, with a large number of lost GRBs. Then, we proposed to study the feasibility of a 4 m fast pointing class telescope, equipped with a multichannel imagers, from Visible to Near Infrared. In this paper, we present the main result of the feasibility study we performed so far.

A number of scientific observations take advantage of the use of robotic, fast pointing telescopes; in particular, fast reacting small telescopes were especially useful for gamma ray burst follow-up which now require better performances and greater telescope size. However, increasing telescope size could imply some limitations in terms of operability and technological solutions. In order to select the best telescope configuration it is necessary to take into account mechanical set up, pointing strategy, wind effects and the resulting effective costs. This paper will investigate and compare the characteristics of traditional alt-az and alt-alt telescope configurations considering also an innovative alt-alt set up to be developed as an alternative to the mainstream layout of present medium class telescopes. In the alt-alt case the system exploits the heritage of larger telescope projects like LBT, coupled with a more traditional fork mounted to match the alt-alt kinematics, so obtaining a more stable machine and minimizing the blind spot limitation.

A prototype for a compact and relatively simple system capable to measure the refraction index of glasses, between 0.4 to 1.7 micron, at room and cryogenic temperatures (T=100-300 K), with an absolute precision of few parts of 100'000 has been developed at INAF facilities in Merate. It is based onto the measurement of the deviation angle of monochromatic light passing through a prism sample placed in the cryogenic chamber. The precision of the measurements depends on many factors, in particular the angle measurement and the thermal stability. Different subsystems have been studied to keep all these parameters under accurate control. One of the main issues has been the trade-off between the simplicity of the set-up and the precision of the refractive index measurement.

Luca Pasquini, A. Manescau, G. Avila, B. Delabre, H. Dekker, J. Liske, S. D’Odorico, F. Pepe, M. Dessauges, C. Lovis, D. Megevand, D. Queloz, S. Udry, S. Cristiani, P. Bonifacio, P. Dimarcantonio, V. D’Odorico, P. Molaro, E. Vanzella, M. Viel, M. Haehnelt, B. Carswell, M. Murphy, R. Garcia-Lopez, J.M. Herreros, J. Perez, M.R. Zapatero, R. Rebolo, G. Israelian, E. Martin, F. Zerbi, P. Spano, S. Levshakov, N. Santos and S. Zucker

To achieve very-high spectral resolution (R > 100 000) with large telescopes (D > 8 m) new solutions have been investigated, like anamorphic pupil slicing, elliptical pupils, slanted VPH gratings, starting from the initial design of CODEX, as proposed by B. Delabre. Generally, for a given slit width, the spectral resolution of a spectrograph is proportional to the length of the grating and inversely proportional to the telescope diameter. For ESPRESSO, as in CODEX, a trick has been used: i.e. to slice the pupil, allowing to reduce the grating length by a factor two. The price to pay is a detector area that is larger by the same amount. An anamorphic cross-disperser is used to create a fast beam in the cross-dispersion direction and so reduce the required detector area.

The effects of atmospheric dispersion are well known in astrometry and astronomical spectroscopy. To reduce these effects, glass prisms are used. Two different prisms, coupled together, give better corrections. However glass dispersion curves do not match very well the dispersion of the atmosphere and secondary spectrum of the order of 50-100 milliarcseconds (mas) or more will be present. I propose a method to find solutions with residuals less than few parts of 10 milliarcsecond and I show some results.