The second generation of ELT instruments includes an optical-infrared high-resolution spectrograph, ANDES, ArmazoNes high Dispersion Echelle Spectrograph. It covers a wide spectral range that goes from 0.4 to 1.8μm (goal 0.35 to 2.4μm). A common model of detector is planned for the two visible spectrographs RIZ and UBV. A total of five detectors will cover the latter spectral range. A common detector unit design has been developed based on ELT's standard components and inspired by the previous successful detector units designed for HARPS and ESPRESSO. It consists of a 9k x 9k CCD detector, a differential vacuum cryostat that keeps the detector in its dedicated vacuum chamber and a cryocooler that cools down the detector to minimize the dark noise. The required temperature, mechanical and pressure stabilities drive the design of the detector unit.
The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 μm with the goal of extending it to 0.35-2.4 μm with the addition of an U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allows ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states.
We present the design of the ANDES UBV module, the bluest spectrograph of the ANDES instrument. It is a fiber-fed high resolution, high stability spectrograph, which will be installed on the ELT-Nasmyth platform to minimize blue fibre losses from the focal plane to the spectrograph. In this paper we present the status of development of the spectrograph, its optical design, and auxiliary devices like exposure meter and leveling system, at the preliminary design stage. As stability is the prime design driver, a thermal enclosure is provided to keep temperature of the optical train stable at ambient conditions, and the pressure is kept constant at high vacuum level. The science, sky background and simultaneous calibration light is fed to the spectrographs via fiber bundles of 66 fibres, which are arranged in a straight row forming the spectrograph slit.
The Large Binocular Telescope, with its expansive collecting area, angular resolving power, and advanced optical design, provides a robust platform for development and operation of advanced instrumentation for astronomical research. The LBT currently hosts a mature suite of instruments for spectroscopy and imaging at optical through mid-infrared wavelengths, supported by sophisticated adaptive optics systems. This contribution summarizes the current state of instrumentation, including upgrades to existing instruments and commissioning of second generation instruments now in progress. The LBT is soliciting proposals for next generation instrument concepts, with participation open to consortium members and others interested in participation in the Observatory.
The first generation of ELT instruments include an optical-infrared High Resolution Spectrograph, formerly indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). Its modular design allows to position the calibration unit and the red & infrared spectrograph modules in the Coude room of the ELT for better thermal and mechanical stability. But to accommodate for a better UV throughput, the blue spectrograph module (UBV) will be positioned on the Nasmyth-platform of the telescope along with the front end of the system. We present the preliminary optical design of this UBV module, which extends the 400 nm blue cutoff of the baseline design to 350 nm by adding a third (the U-) arm. In addition to classical image quality calculations, we produce echelle-footprints which can be analyzed like regular observations.
The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs (UBV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 µm with the goal of extending it to 0.35-2.4 µm with the addition of a K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Its modularity will ensure that ANDES can be placed entirely on the ELT Nasmyth platform, if enough mass and volume is available, or partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of more than 200 scientists and engineers which represent the majority of the scientific and technical expertise in the field among ESO member states.
ELT-HIRES (High Resolution Spectrograph for the Extremely Large Telescope) is a multifold fiber-fed spectrograph planned for the Nasmyth B focal station on ELT, covering a wavelength range between 0.4 and 1.8 μ. One of the most relevant science cases is represented by the detection of life signature in the extrasolar atmospheres for Earth-like planets. The polarimetric unit, feeding the UBVRI and the zYJH spectrograph modules, will consist of two subassemblies: the main one, aimed to be installed in the intermediate focus, will host the polarizer (a double Wollaston calcite prism) and the retarder plates splitting the optical beam into the four Stokes vector components; the other will be located in one of the four dedicated arms of the Front End on the Nasmyth platform, providing the atmospheric dispersion correction, field stabilization and selection of the operating modes before the fiber injection. At the conclusion of Phase A, we have presented this as the optimal design solution fulfilling the top level requirement of reaching a sensitivity of 10-5 S/I (S being equivalent to one of the Stokes vectors), a condition achievable only if the polarizers are installed in a rotationally symmetric focus. The current work, which can be considered a continuation of two preceding papers, illustrates new simulation results from the development of the polarization-ray-tracing tool. We have included also the crystal anisotropic properties of the polarizing components, analyzing the transmission loss that the light beam encounters propagating through the optical train before entering the fiber bundles in the different operating modes, bearing in mind the polarimetric aberrations induced by the active compensation of the primary mirror and the loads contributing as Zernike polynomials of different orders, namely the telescope cross-talk.
The current STELLA Échelle spectrograph (SES), which records 390nm to 870nm in one shot at a spectral resolution of 55000, will be replaced by a suite of specialized spectrographs in three spectral bands. The UV will be covered by a newly designed H and K spectrograph covering 380nm to 470nm (SES-H and K), the visual band (470nm - 690 nm) will be covered by SES-VIS, which is a vacuum-stabilized spectrograph designed for high radial-velocity accuracy, and the NIR will be covered by the current SES spectrograph from 690nm to 1050 nm. In order to improve the UV transmission, and to accommodate three different fibre-feeds, the prime focus corrector of the telescope will be refurbished, leading to an optical system with the f/2 1200mm spherical primary, a 4-lens collimator with 2" aperture, atmospheric dispersion corrector (ADC), and two dichroic beam splitters, feeding 3 separate fibre feeds for the three bands. The newly designed H and K spectrograph will be an Échelle spectrograph, based on a R4-grating with 41.6 l/mm and 110mmx420mm, using a f/5 camera and the cross-disperser in double pass (as in TRAFICOS, MIKE, KPF), using 21 spectral orders. The spectral resolution of all three spectrographs will be comparable to the current SES's 55000.
HIRES is the high-resolution spectrograph of the European Extremely Large Telescope at optical and near-infrared wavelengths. It consists of three fibre-fed spectrographs providing a wavelength coverage of 0.4-1.8 µm (goal 0.35-2.4 µm) at a spectral resolution of 100,000. The fibre-feeding allows HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU in the NIR. Therefore, it will be able to operate both in seeing- and diffraction-limited modes. Its modularity will ensure that HIRES can be placed entirely on the Nasmyth platform, if enough mass and volume is available, or part on the Nasmyth and part in the Coud`e room. ELT-HIRES has a wide range of science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars (PopIII), tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The HIRES consortium is composed of more than 30 institutes from 14 countries, forming a team of more than 200 scientists and engineers.
The new visual STELLA echelle spectrograph (SES-VIS) is a new instrument for the STELLA-II telescope at the Iza~na observatory on Tenerife. Together with the original SES spectrograph - which will still be used in the near IR - and a new H&K-optimized spectrograph, which is currently in the design phase, it will change the focus of the spectroscopic observations at STELLA towards the follow up of planetary candidates detected by upcoming surveys focusing on bright targets (TESS, PLATO2). It is optimized for precise radial velocity determination and long term stability. We have developed a ZEMAX based software package to create simulated spectra, which are then extracted using our new reduction package, which is based on the PEPSI software package. The focus has been put on calibration spectra, and the full range of available calibration sources (at field, Th-Ar, and Fabry-Perot), which can be compared to actual commissioning data once they are available. Furthermore we tested for the effect of changes of the environmental parameters to the wavelength calibration precision.
ELT-HIRES (High Resolution Spectrograph for the Extremely Large Telescope) is a multifold fiber-fed spectrograph planned for the Nasmyth B focal station on ELT, with a large spectral coverage, ranging from 0.4 to 1.8 μ. It’s our intention to equip it with a full Stokes polarimetric facility, feeding the UBVRI and the zYJH bands. Among the most relevant scientific targets there is the detection of life signature in the extrasolar atmospheres for Earth-like planets. The polarimetric instrument will consist of two subunits: the main one intended to be installed in the intermediate focus where the optical beam is split into the two polarized components via a double Wollaston calcite prism; the other one installed in one of the four arms of the Front End on the Nasmyth platform, in charge of the atmospheric dispersion correction, field stabilization and selection of the operating modes before the fiber injection. This has been presented for the Phase A as the only possible design solution fulfilling the top level requirement of reaching a sensitivity of 10-5 S/I (with S equivalent to one of the Stokes vectors), condition achievable only if the polarizers are installed in a rotationally symmetric focus. In the present work we illustrate novel simulations of the polarized aberrations based on an integration of the structural and thermal FEM analysis within a Zemax design with the help of Matlab and Python tools.
White pupil arrangements using parabolic off-axis mirrors are commonly used by instrument designers of high-resolution spectrographs. Their advantage is a non-chromatic, spherical free collimation, an intermediate focus providing the possibility for stray light apertures, and the compression of the beam diameter using a second, a transfer, collimator. However, these arrangements suffer from off-axis aberrations in the field. Many configurations create the intermediate focus, after double-passing the primary collimator, in the vicinity of the spectrograph input. This makes it necessary to introduce small angles at the main collimator, further increasing off-axis aberrations. Furthermore, image curvature is high and requires toroidal surfaces to be added near the spectrograph focus in front of the CCD. In high-precision radial velocity measurements, it is of great importance to properly model the spectrographs transfer function in order to derive exact line positions. Therefore, clean and very well defined spots, even when working near the sampling limit, which can simply be represented by gaussians will benefit such measurements. This point is usually considered less by instrument designers. We have studied several possible off-axis mirror arrangements for white pupil spectrographs and discuss our results here. We focus on the image quality generated by the mirrors, on-axis as well as in the field. We come to the conclusion that a fairly uncommon arrangement provides best performance in the sense of image quality and focus accessibility.
The Phase A study for the high-resolution spectrograph for the Extremely Large Telescope (ELT-HIRES) has been concluded in late 2017. We present the main outcome for a polarimetric light feed from the intermediate focus (IF) and a Nasmyth focus of the telescope. We conclude that the use of the IF is mandatory for high-precision spectropolarimetry. Among the description of the product tree, we present phase-A level opto-mechanical designs of the subunits, describe the observational and calibration modes, the PSF error budget, and the preliminary FEM structural and earthquake analysis.
An update on the development of a ray tracing polarimetric simulator to estimate the instrumental polarization including both the telescope mirrors and the optical elements of the polarimeter is reported. Trade-off strategies and ongoing solutions in view of the Phase B are outlined too.
The Gregor At Night Spectrograph (GANS) is a new instrument currently being built for the GREGOR solar telescope at Iza~na observatory on Tenerife. Its primary science case will be the follow up of planetary candidates detected by upcoming surveys focussing on bright targets (TESS, PLATO2). Therefore it will be optimised for precise radial velocity determination and long term stability. We have developed a ZEMAX based software package to create simulated spectra, which are reduced using standard IRAF tasks. We used a solar model spectrum to determine the influence of S/N ratio, wavelength coverage, pixel sampling and telluric lines on the extracted radial velocities. Furthermore we derived the effect of an asymmetric spectrograph illumination on the measured radial velocity.
We present the optical design of the ELT polarimeter in the context of the Phase-A study for HIRES. It is well known that in order to reduce the instrumental polarization and cross-talk, the optimal position for a polarimeter along the optical path of a telescope is the rotationally symmetric focus.
In the particular case of ELT this is represented by the intermediate focus (IF) below M4 which is not directly accessible and needs therefore a reimaging to a safety distance of at least 500 mm. The design of a transfer optics unit for such location is challenging due to the constraint of having an allowed vignetting area of maximum 5 arc min. We focus in our paper on two optical design solutions.
The first one is deploying a double Cassegrain system to reimage the IF, which includes the polarization optics and feeds the other ELT mirrors, redirecting the ordinary and extraordinary beams to the front end module (FE) onto the Nasmyth focus. This module comprises components for sky derotation, atmospheric dispersion correction (ADC), wavelength splitting in two bands (UBVRI, zYJH), field stabilization and conversion to f/20, dispatching the light into two pairs of fiber bundles to feed the HIRES spectrograph.
The other solution considers a fiber based compact IF module, using a Schwarzschild Collimator with Foster prism, ADC and beam splitters for the two spectral bands. The two polarized beams are sent by pupil imaging through four separate long fibers to the fiber link module of the spectrograph. There we convert the output fiber f ratio from f/2.5 to f/20.
We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution Spectrograph for ELT, which has just been completed by a consortium of 30 institutes from 12 countries forming a team of about 200 scientists and engineers. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature’s fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists in a modular fiber- fed cross-dispersed echelle spectrograph with two ultra-stable spectral arms providing a simultaneous spectral range of 0.4-1.8 μm at a spectral resolution of ~100,000. The fiber-feeding allows ELT-HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU.
PEPSI is the new fiber-fed and stabilized “Potsdam Echelle Polarimetric and Spectroscopic Instrument” for the Large Binocular Telescope (LBT). It covers the entire optical wavelength range from 384 to 913 nm in three exposures at resolutions of either R=λ/▵λ=50,000, 130,000 or 250,000. The R=130,000 mode can also be used with two dual-beam Stokes IQUV polarimeters. The 50,000-mode with its 12-pix sampling per resolution element is our “bad seeing” or “faint-object” mode. A robotic solar-disk-integration (SDI) telescope feeds solar light to PEPSI during day time and a 450-m fiber feed from the 1.8m VATT can be used when the LBT is busy otherwise. CCD characterization and a removal procedure for the spatial fixed-pattern noise were the main tasks left from the commissioning phase. Several SDI spectral time series with up to 300 individual spectra per day recovered the well-known solar 5-minute oscillation at a peak of 3 mHz (5.5min) with a disk-integrated radial-velocity amplitude of only 47 cm/s. Spectral atlases for 50 bright benchmark stars including the Sun were recently released to the scientific community, among them the ancient planet- system host Kepler-444. These data combine PEPSI’s high spectral resolution of R=250,000 with signal-to-noise ratio (S/N) of many hundreds to even thousands covering the entire optical to near-infrared wavelength range from 384 to 913 nm. Other early science cases were exoplanet transits including TRAPPIST-1, a spectrum of Boyajian's star that revealed strong and structured but stable ISM Na D lines, a spectrum of Oph allowing a redetermination of the ISM Li line doublet, and a first Doppler image of the young solar analog EK Dra that revealed starspots with solar-like penumbrae.
GREGOR at night spectrograph (GANS) is a high-resolution thermally-stabilised vacuum-enclosed fixed-format fiber-fed Echelle spectrograph. GANS will be installed starting 2018 alongside the daytime instrumentation in the building of the 1,5m Gregor Solar Telescope at the Observatorio del Teide at Izan˜a, Tenerife. Specified resolving power is R~55k with wavelength coverage from 470 to 680 nm in single shot on 2k 2k CCD with 3”, 50μm fiber on sky, and with space between orders for simultaneous calibration light in the form of a Fabry-Perot Etalon or a Laser-comb spectrum. The end-to-end simulated radial velocity precision performance estimate is 2 ms−1. The main observing project of GANS will be the ground-based follow-up survey of TESS and PLATO2.0 exoplanet candidates. GANS will observe its targets in autonomous operation without human intervention using the normally human-operated day-time observatory. Limited operations will begin in first half of 2019 with first science-light planned for summer 2019.
We introduce the opto-mechanical architecture of a high precision, full Stokes vector, dual-channel polarimeter for the
European Extremely Large Telescope’s High Resolution spectrograph (E-ELT HIRES). It is foreseen to feed two
spectrograph modules simultaneously through the standard Front End subunit located on the Nasmyth platform via two
fiber bundles; one optimized for the optical (BVRI), the other optimized for the infrared (zYJH) bands. The polarimeter
is located below M4 in the f/4.4 intermediate focus, representing the only rotationally symmetric focus available, and is
retractable. We illustrate the strategy of repositioning and aligning the instrument, provided that it has to withstand wind
and earthquake loads and that the PSF is varying in width and position due to the active compensation by the co-phasing
corrections. Preliminary results of its expected polarimetric sensitivity and accuracy are also analyzed for several
configurations of M1 segments and suggest a stunning performance in the intermediate focus with cross talks of the
order of 10-7 but 10-2 if it were located in the Nasmyth focus.
A full Stokes dual channel polarimeter for the E-ELT HIRES spectrograph has been envisioned for the intermediate focus f/4.4, operating within a spectral range of 0.4-1.6 μ. It will feed the EELT- HIRES instrument located on the Nasmyth platform via two pairs of dedicated fibers: one fibre pair optimized for the BVRI, the other one optimized for the JH band or any other feasible combination. The instrument must be retractable within a workspace in fulfillment with the ESO requirements on the allocated volume and the dynamic response of the AO tower. For such purpose a swinging arm has been designed with a rotation provided by 5 revolute joints and a jackscrew. Moreover repeatability in repositioning has to be guaranteed by a parallel manipulator, performing an alignment procedure mainly along 5 axes. Dynamics and control criteria with a feed forward chain to compensate for vibration forces and feedback chain for tracking procedure are hereafter presented.
The first generation of E-ELT instruments will include an optic-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.
GRAPE is the polarimeter planned to be installed on the main Cassegrain focus of GTC (Gran Telescopio Canarias), having an equivalent entrance pupil of 10.4 m, located at the Observatorio del Roque de los Muchachos (ORM) , in La Palma, Canary Islands. It’s meant to deliver full Stokes (IQUV) polarimetry covering the spectral range 0.420-1.6 μ, in order to feed the HORS instrument (High Optical Resolution Spectrograph), mounted on the Nasmyth platform, which has a FWHM resolving power of about 25,000 (5 pixel) designed for the wavelength range of 380-800 nm. Two calcite blocks and a BK-7 prism arranged in a Foster configuration are splitting the Ø12.5mm collimated beam into the ordinary and extraordinary components. The entire subunit from the Foster prisms down to the input fibers is rotated by steps of 45 degrees in order to retrieve Q, U components. By inserting a quarter wave retarder plate before the entrance to the Foster unit circular polarization is measured too.
The current paper consist of two main parts: at first CFD simulations are introduced, which have been run compliant to the specifications derived by the environmental conditions and the transient thermal gradients taking into account the presence of the electronic cabinets installed, which are triggering the boundary conditions for the outer structure of the instrument; then a thermal control model is proposed based on heat exchangers to stabilize the inner temperature when compensation via passive insulation is not enough. The tools that have been adopted to reach for such goal are Ansys Multiphysics, in particular CFX package and Python scripts.
A waveguide image slicer with resolutions up to 270.000 (planned: 300.000) for the fiber fed PEPSI echelle spectrograph at the LBT and single waveguide thicknesses of down to 70 μm has been manufactured and tested. The waveguides were macroscopically prepared, stacked up to an order of seven and thinned back to square stack cross sections. A high filling ratio was achieved by realizing homogenous adhesive gaps of 3.6 μm, using index matching adhesives for TIR within the waveguides. The image slicer stacks are used in immersion mode and are miniaturized to enable implementation in a set of 2x8. The overall efficiency is between 92 % and 96 %.
Limited observing time at large telescopes equipped with the most powerful spectrographs makes it almost impossible to gain long and well-sampled time-series observations. Ditto, high-time-resolution observations of bright targets with high signal-to-noise are rare. By pulling an optical fibre of 450m length from the Vatican Advanced Technology Telescope (VATT) to the Large Binocular Telescope (LBT) to connect the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) to the VATT, allows for ultra-high resolution time-series measurements of bright targets. This article presents the fibre-link in detail from the technical point-of-view, demonstrates its performance from first observations, and sketches current applications.
STELLA is a robotic observatory on Tenerife housing two 1.2m robotic telescopes. One telescope is fibre-feeding a high-resolution (R=55,000) échelle spectrograph (SES), while the other telescope is equipped with a visible wide- field (FOV=22' x 22') imaging instrument (WiFSIP). Robotic observations started mid 2006, and the primary scientific driver is monitoring of stellar-activity related phenomena. The STELLA Control System (SCS) software package was originally tailored to the STELLA roll-off style building and high-resolution spectroscopy, but was extended over the years to support the wide-field imager, an off-axis guider for the imager, separate acquisition telescopes, classical domes, and targets-of-opportunity. The SCS allows for unattended, off-line operation of the observatory, targets can be uploaded at any time and are selected based on merit-functions in real-time (dispatch scheduling). We report on the current status of the observatory and the current capabilities of the SCS.
The GTC (Gran Telescopio Canarias), with an equivalent aperture of 10.4 m, effective focal length of 169.9 m, located at
the Observatorio del Roque de los Muchachos , in La Palma, Canary Islands, will host on its Cassegrain focus the
GRAPE polarimeter (GRAntecan PolarimEter). At such focus the plate scale is 1.21 arcsec/mm and the unvignetted
FOV 8 arcmin. The instrument will provide full Stokes polarimetry in the spectral range 380-1500 nm, feeding
simultaneously up to two spectrographs. At the moment an interface to HORS (High Optical Resolution Spectrograph) is
being defined, located on the Nasmyth platform, it has a FWHM resolving power of about 25,000 (5 pixel) within a
spectral range of 400-680 nm. The rotator and instrumental flanges for the Cassegrain focus are currently under
definition. Hereafter I present the state of art of the mechanical design of the polarimeter, whose strategy is based on an
integrated model of Zemax design into ANSYS FEM static and dynamic analyses with thermal loads applied, in order to
retrieve tip-tilt, decentering errors and other significant parameters to be looped back to the Zemax model. In such a way
it is possible to compare and refine the results achieved through the tolerance analysis.
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.
The STELLA project is made up of two 1.2m robotic telescopes to simultaneously monitor stellar activity
using a high-resolution spectrograph on one telescope, and an imaging instrument on the other telescope. The
STELLA Echelle spectrograph (SES) along with the building has been in operation successfully since 2006, and
is producing spectra covering the visual wavelength range between 390 and 900 nm at a resolution of 55 000. The
stability of the spectrograph over the entire two year span, measured by monitoring 15 radial velocity standard
stars, is 30 to 150 m/s rms. The Wide-field stellar imager and photometer (WIFSIP) was put into operation in
2010, when the SES-lightfeed was physically moved to the second telescope. We describe the final instrument
conguration in use now, and on the efficiency of the robotic scheduling in use at the observatory.
We present a conceptual design for a spectropolarimetric focal station for ESO's European Extremely Large Telescope
(E-ELT). It uses the intermediate f/4.4 focus, the only symmetric focus of the telescope. A dual channel, full Stokesvector
polarimeter provides on-axis light for the wavelength range 380-1600nm to up to two spectrographs
simultaneously via two pairs of fibers. With such spectropolarimetric capability and a proper spectrograph for the optical
and the near infrared wavelengths, the E-ELT would be able to provide the full parameter space of an incoming
wavefront. Because of the on-axis entrance location of the polarimeter collimator and an entrance aperture of just 1.3
arcsec, the expected poor image quality of the intermediate telescope focus is not directly relevant.
The All Sky Infrared Visible Analyzer (ASIVA) is an instrument principally designed to characterize sky con-
ditions for purposes of improving ground-based astronomical observational performance. The ASIVA's primary
functionality is to provide radiometrically calibrated imagery across the entire sky over the mid-infrared (IR)
spectrum (8-13 μm). Calibration procedures have been developed for purposes of quantifying the photometric
quality of the sky. These data products are used to provide the STELLA scheduler with real-time measured
conditions of the sky/clouds, including thin cirrus to better optimize observing strategy. We describe how this
can be used in the denition of the observing programs to make best use of the telescope time. Additional
research is underway to correlate infrared spectral radiance with visible-spectrum extinction.
The two spectropolarimeters for PEPSI (Potsdam Echelle Polarimetric and Spectroscopic Instrument) have been de¬signed in order to reconstruct the full Stokes vector measuring linear and circular polarization simultaneously with a re¬solving power of 120,000. The polarimeters will be attached to the Gregorian focus of the so far largest LBT 2x8.4m telescope and will feed together with permanent focus stations the spectrograph via 44m long fibers connection. The spectrograph will be located in a pressure-temperature controlled chamber within the telescope pier. We present hereafter the last results from combined structural and CFD analyses in order to fulfill the optical requirements.
The International Concordia Explorer Telescope (ICE-T) is two 60cm wide-field robotic Schmidt telescopes optimized
for high-precision CCD photometry in two separate bandpasses. The project is under final design by an international
consortium led by the Astrophysical Institute Potsdam, Germany, and was foreseen to be placed at the French-Italian
Concordia Station on Dome C in Antarctica. Its core scientific objective would be to detect and investigate the combined
effects of extra-solar planets, stellar magnetic activity and non-radial pulsations on the structure and evolution of stars.
We present the optical, the mechanical, and the electronic design of the telescope and lay out the operational constraints
for its search for extrasolar planets and magnetic stellar activity.
ICE-T, the International Concordia Explorer Telescope, is under final design by an international consortium led by the
Astrophysical Institute Potsdam AIP, Germany, and is intended to be placed at the French-Italian Concordia Station on
Dome C in Antarctica. Experience with smaller telescopes at Concordia has shown that under the weather conditions at
this site - with mean outside temperatures of -60° to -80° C and temperature changes of 20° in short time intervals - the
ice-accumulation on the optical components during observation is a major problem. Also, energy consumption at this site
should be minimized because fuel transport to the site is very costly. The paper describes the thermal concept for the
telescope where the waste energy of the instrument electronics is used for heating the front surfaces of the Schmidt optics.
All other parts of the telescope are protected by an insulated smooth cladding against the harsh outside environment.
The effectiveness of the thermal concept is verified by CFD (Computer Fluid Dynamics) calculations.
With the integration of a 1-meter Cesic primary mirror the GREGOR telescope pre-commissioning started. This is the
first time, that the entire light path has seen sunlight.
The pre-commissioning period includes testing of the main optics, adaptive optics, cooling system, and pointing system.
This time was also used to install a near-infrared grating spectro-polarimeter and a 2D-spectropolarimeter for the visible
range as first-light science instruments. As soon as the final 1.5 meter primary mirror is installed, commissioning will be
completed, and an extended phase of science verification will follow. In the near future, GREGOR will be equipped with
a multi-conjugate adaptive optics system that is presently under development at KIS.
We present the status of PEPSI, the bench-mounted fibre-fed and stabilized "Potsdam Echelle Polarimetric and
Spectroscopic Instrument" for the 2×8.4m Large Binocular Telescope in southern Arizona. PEPSI is under construction
at AIP and is scheduled for first light in 2009/10. Its ultra-high-resolution mode will deliver an unprecedented spectral
resolution of approximately R=310,000 at high efficiency throughout the entire optical/red wavelength range 390-1050nm without the need for adaptive optics. Besides its polarimetric Stokes IQUV mode, the capability to cover the
entire optical range in three exposures at resolutions of 40,000, 130,000 and 310,000 will surpass all existing facilities in
terms of light-gathering-power times spectral-coverage product. A solar feed will make use of the spectrograph also
during day time. As such, we hope that PEPSI will be the most powerful spectrometer of its kind for the years to come.
Waveguide image-slicer prototypes with resolutions up to 310.000 for the fiber fed PEPSI echelle spectrograph at the
LBT and single waveguide thicknesses of down to 30 μm have been manufactured. The waveguides were
macroscopically prepared, stacked up to an order of 7 and thinned back to square stack cross sections. A high filling ratio
was achieved by realizing homogenous adhesive gaps of 4.6 μm, using index matching adhesives for TIR within the
waveguides. The image-slicer stacks can be used in immersion mode and are miniaturized to be implemented in a set of
four, measurements indicate an overall efficiency of above 80% for them.
The STELLA project consists of two robotic 1.2m telescopes to simultaneously monitor stellar activity with a high resolution echelle spectrograph on one telescope, and a photometric imaging instrument on the other telescope. The STELLA observatory is located at the Observatorio del Teide on the Canary island of Tenerife. The STELLA Echelle spectrograph (SES) has been operated in robotic mode for two years now, and produced approximately 10,000 spectra of the entire optical range between 390 and 900 nm at a spectral resolution of 55,000 with a peak shutter-open time of 93%. Although we do not use an iodine cell nor an actively stabilized chamber, its average radial velocity precision over the past two years was 60 to 150m/s rms, depending on target. The Wide-Field STELLA Imaging Photometer (WIFSIP) is currently being tested and will enter operation early 2009. In this paper, we present an update report on the first two years of operation.
Small IRAIT is a 25 cm Cassegrain telescope, installed at Dome C, on the high Antarctic
plateau, during 2007 winter campaign. It performed a first test of multiband (UBVRI) photometry
from Dome C, taking advantage of its remote control system that allowed a 10 days,
98% duty cycle run on a chromospherically active, spotted star in Cen (V841); it also tested
multiband acquisition on open clusters, AGB stars, blazars (PKS2155), eclipsing binaries. In
situ optimization made the telescope able to operate in the cold, harsh Antarctic environment.
Thanks to exceptional coldness, low sky brightness and low content of water vapour of the above atmosphere Dome C,
one of the three highest peaks of the large Antarctic plateau, is likely to be the best site on Earth for thermal infrared
observations (2.3-300 μm) as well as for the far infrared range (30 μm-1mm). IRAIT (International Robotic Antarctic
Infrared Telescope) will be the first European Infrared telescope operating at Dome C. It will be delivered to Antarctica
at the end of 2006, will reach Dome C at the end of 2007 and the first winter-over operation will start in spring 2008.
IRAIT will offer a unique opportunity for astronomers to test and verify the astronomical quality of the site and it will be
a useful test-instrument for a new generation of Antarctic telescopes and focal plane instrumentations. We give here a
general overview of the project and of the logistics and transportation options adopted to facilitate the installation of
IRAIT at Dome C. We summarize the results of the electrical, electronics and networking tests and of the sky
polarization measurements carried out at Dome C during the 2005-2006 summer-campaign. We also present the 25 cm
optical telescope (small-IRAIT project) that will installed at Dome C during the Antarctic summer 2006-2007 and that
will start observations during the 2007 Antarctic winter when a member of the IRAIT collaboration will join the Italian-French Dome C winter-over team.
The integration of the three main silicon carbide mirrors into the new 1.5 m solar telescope GREGOR at Izana on Tenerife, Spain is planned during 2006. We expect first light at the end of 2006. A progress report about integration of the optics and mechanics and planning of the commissioning phase of the telescope and post focus instruments will be presented at the meeting. The GREGOR telescope is build by a consortium of the Kiepenheuer Institut fur Sonnenphysik in Freiburg, the Astrophysikalische Institut Potsdam, the Institut fur Astronomie Gottingen and additional national and international Partners.
The telescope structure including control system and the complete retractable dome of the new 1.5 m solar telescope GREGOR were assembled during 2004 at Izana on Tenerife, Spain. The GREGOR telescope is build by a consortium of the Kiepenheuer Institut fuer Sonnenphysik, the Astrophysikalische Institut Potsdam, the Institut fuer Astrophysik Goettingen and additional national and international Partners. Pointing, tracking and thermal tests were made to verify the proposed performance. The results of these tests and a progress report of the project will be presented.
We investigate the potential of using adaptive optics (AO) in the V, R, and I bands to reach ultra-high resolution (UHR, R ≥ 200,000) in echelle spectrographs at 8-10m telescopes. In particular, we investigate the possibility of implementing an UHR mode for the fiber-fed spectrograph PEPSI (Potsdam Echelle Polarimetric and Spectrographic Instrument) being developed for the Large Binocular Telescope (LBT). By simulating the performances of the advanced AO system that will be available at first light at the LBT, and by using first-order estimates of the spectrograph performances, we calculate the total efficiency and signal to noise ratio (SNR) of PEPSI in the AO mode for stars of different magnitudes, different fiber core sizes, and different fractions of incident light diverted to the wavefront sensor. We conclude that AO can provide a significant advantage, of up to a factor ~2 in the V, R and I bands, for stars brighter than mR ~ 12 - 13. However, if these stars are observed at UHR in non-AO mode, slit losses caused by the need to use a very narrow slit can be compensated more effectively by the use of image slicers.
PEPSI is a high-resolution, fiber fed echelle spectrograph with polarimetric capabilities for the LBT. In order to reach a maximum resolution R=120.000 in polarimetric mode and 300.000 in integral light mode with high efficiency in the spectral range 390-1050~nm, we designed a white-pupil configuration with Maksutov collimators. Light is dispersed by an R4 31.6 lines/mm monolithic echelle grating mosaic and split into two arms through dichroics. The two arms, optimized for the spectral range 390-550~nm and 550-1050~nm, respectively, consist of Maksutov transfer collimators, VPH-grism cross dispersers, optimized dioptric cameras and 7.5K x 7.5K 8~μ CCDs. Fibers of different core sizes coupled to different image-slicers allow a high throughput, comparable to that of direct feed instruments. The optical configuration with only spherical and cylindrical surfaces, except for one aspherical surface in each camera, reduces costs and guarantees high optical quality. PEPSI is under construction at AIP with first light expected in 2006.
GREGOR is the new 1.5 m solar telescope assembled on Tenerife, Spain, by the German consortium of the Kiepenheuer Institut fur Sonnenphysik, the Astronomischen Institut Potsdam, the Universitats-Sternwarte Gottingen and other national and international Partners. The refurbishment of the building is almost finished. The manufacturing of the telescope structure and the optics is still in progress. After the integration of the new complete retractable dome in July 2004 the telescope structure, optic and post focus instruments will be assembled during the rest of the year. First light is planned during May 2005.
We present a preliminary design study for a high-resolution echelle spectrograph (ICE) to be used with the spectropolarimeter PEPSI under development at the LBT. In order to meet the scientific requirements and take full advantage of the peculiarities of the LBT (i.e. the binocular nature and the adaptive optics capabilities), we have designed a fiber-fed bench mounted instrument for both high resolution (R ≈ 100,000; non-AO polarimetric and integral light modes) and ultra-high resolution (R ≈ 300,000; AO integral light mode). In both cases, 4 spectra per order (two for each primary mirror) shall be accomodated in a 2-dimensional cross dispersed echelle format. In order to obtain a resolution-slit product of ≈ 100,000 as required by the science case, we have considered two alternative designs, one with two R4 echelles in series and the other with a sigle R4 echelle and fiber slicing. A white-pupil design, VPH cross-dispersers and two cameras of different focal length for the AO and non-AO modes are adopted in both cases. It is concluded that the single-echelle fiber-slicer solution has to be preferred in terms of performances, complexity and cost. It can be implemented at the LBT in two phases, with the long-camera AO mode added in a second phase depending on the availability of funds and the time-scale for implementation of the AO system.
PEPSI (Postham Echelle Polarimetric and Spectroscopic Instrument) is to use the unique feature of the LBT and its powerful double mirror configuration to provide high and extremely high spectral resolution full-Stokes four-vector spectra in the wavelength range 450-1100nm. For the given aperture of 8.4m in single mirror mode and 11.8m in double mirror mode, and at a spectral resolution of 40,000-300,000 as designed for the fiber-fed Echelle spectrograph, a polarimetric accuracy between 10-4 and 10-2 can be reached for targets with visual magnitudes of up to 17th magnitude. A polarimetric accuracy better than 10-4 can only be reached for either targets brighter than approximately 10th magnitude together wiht a substantial trade-off wiht the spectral resolution or with spectrum deconvolution techniques. At 10-2, however, we will be able to observe the brightest AGNs down to 17th magnitude.
We describe the operations model for our two robotic photoelectric telescopes and give a brief status report after more than three years of routine operation in southern Arizona. The telescopes operate fully unattended, also the observatory itself is automatic. A site-control computer monitors weather sensors and operates the roof while the telescope control computers operate the photometers and accept input files from and provides nightly observations to the astronomer in Vienna. In the first three years of operation a total of 3.3 million individual scientific measurements were made.
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