The MeerKAT+ (MK+) project will extend the current MeerKAT array at the South African Radio Astronomy Observatory (SARAO) site in the Karoo region of South Africa.
The South African MeerKAT telescope is a SARAO precursor to the Square Kilometre Array mid-frequency instrument (SKA-MID). The MK+ project is a partnership between SARAO, the Max Planck Society (MPG, MPIfR), and the Istituto Nazionale di Astrofisica (INAF), and is an important milestone towards the SKA-MID array. We will provide details and updates on the MK+ project.
The OARPAF telescope is an 80-cm-diameter optical telescope installed in the Antola Mount Regional Reserve, in Northern Italy. We present the results of the characterization of the site, as well as developments and interventions that have been implemented, with the goal of exploiting the facility for scientific and educational purposes. During the characterization of the site, an average background brightness of 22.40mAB (B filter) to 21.14mAB (I) per arcsecond squared, and a 1.5″ to 3.0″ seeing, have been measured. An estimate of the magnitude zero points for photometry is also reported. The material under commissioning includes three CCD detectors for which we provide the linearity range, gain, and dark current; a 31-orders échelle spectrograph with R ∼ 8500 to 15,000 and a dispersion of n = 1.39 × 10 − 6 px − 1λ + 1.45 × 10 − 4 nm / px, where λ is expressed in nm. The scientific and outreach potential of the facility is proven in different science cases, such as exoplanetary transits and active galactic nuclei variability. The determination of time delays of gravitationally lensed quasars, the microlensing phenomenon, and the tracking and the study of asteroids are also discussed as prospective science cases.
Next-generation infrared astronomical instrumentation for ground-based and space telescopes could be based on MOEMS programmable slit masks for multi-object spectroscopy (MOS). MOS is used extensively to investigate astronomical objects optimizing the Signal-to-Noise Ratio (SNR): high precision spectra are obtained and the problem of spectral confusion and background level occurring in slitless spectroscopy is cancelled. Fainter limiting fluxes are reached and the scientific return is maximized both in cosmology, in galaxies formation and evolution, in stellar physics and in solar system small bodies characterization. We are developing a 2048 x 1080 Digital-Micromirror-Device-based (DMD) MOS instrument to be mounted on the 3.6m Telescopio Nazionale Galileo (TNG) and called BATMAN. A two-arm instrument has been designed for providing in parallel imaging and spectroscopic capabilities. BATMAN will be mounted on the folded Nasmyth platform of TNG. Thanks to its compact design, high throughput is expected. 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. The stiffness of the instrument is guaranteed thanks to a box architecture linking both benches. The volume of BATMAN is 1.4x1.2x0.75 m3, with a total mass of 400kg. Mounting of all sub-systems has been done and integration of the individual arms is under way. 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 new operational procedures on astronomical objects (combining MOS and IFU modes, different spatial and spectral resolutions in the same FOV, absolute (spectro-) photometry by combining imaging and spectroscopy in the same instrument, automatic detection of transients …). This instrument will be placed at TNG by beginning-2019.
ESPRESSO, Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, is now under the assembly, integration and verification phase and will be installed beginning next year at Paranal Observatory on ESO's Very Large Telescopes. The Front End is the modular system in the Combined Coudé Laboratory receiving the light from the four VLT Units, providing the needed connection between the input signal, i.e., object light, sky light, and calibration light, to feed the spectrograph through optical fibers. The modular concept of the FE Units drove the system design and the alignment workflow. We will show the integration method of the single FE modules adopted to guarantee the necessary repeatability between the different Units. The performances of the system in terms of image quality and encircled energy in the observed point spread function are reported. Finally, the strategy followed in the Paranal Combined Coudè Laboratory to define the convergence point of the four UTs is described, along with the procedure used to align the ground plates, the main structure, and the mode selector.
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.
MAORY is one of the four instruments for the E-ELT approved for construction. It is an adaptive optics module offering two compensation modes: multi-conjugate and single-conjugate adaptive optics. The project has recently entered its phase B. A system-level overview of the current status of the project is given in this paper.
The Multi-Conjugate Adaptive Optics module for the European Extremely Large Telescope has been designed to achieve uniform compensation of the atmospheric turbulence effects on a wide field of view in the near infrared. The design realized in the Phase A of the project is undergoing major revision in order to define a robust baseline in view of the next phases of the project. An overview of the on-going activities is presented.
The 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.
This paper presents the Espresso Anamorphic pupil Slicer (APSU) implementation. For ESPRESSO that will be installed
on ESO’s Very Large Telescope (VLT). In this work we will present the design and trade off for the pupil slicing system
introduced in order to increase the resolving power, effectively decreasing slit width. It’s based onto simplified optical
component that introduce large anamorphism while keeping low aberrations by means of cylindrical optics. We describe
here the trade off between slicing through two adjacent squared doublets and two achromatic prisms. Preliminary
integration and procurement is also discussed here.
This paper presents the Espresso Exposure Meter (EM) implementation. ESPRESSO, the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, will be installed on ESOs Very Large Telescope (VLT). The light coming from the Telescope through a Coude Focus of all the Four Telescope Units (UTs) will be collected by the Front End Unit that provides Field and Pupil stabilisation and injects the beams into the Spectrograph fibers. An advanced Exposure Meter system will be used to correct Radial Velocity (RV) obtained from the scientific spectrum for the Earth relative motion. In this work we will present the performance of an innovative concept for the Exposure Meter system based on a Charge Coupled Device (CCD) with a chromatic approach for the calculation of the Mean Time of Exposure (MTE). The MTE is a fundamental quantity used for the correction of RV for the Earth relative motion during exposure. In particular, splitting the light in different chromatic channels on the CCD, we will probe for potential chromatic effects on the calculation of the MTE in each channel and how they could be used in order to perform the correction of RV. The paper is accompanied by a fully described numerical analysis that keeps into view a key performance evaluation for different stellar spectral types (B to M spectral main sequence classes).
The opto-mechanical conceptual design for the Front-End unit and the calibration unit of the ESPRESSO Spectrograph is
described in this paper. The front end system exploits a modular concept. Each FEU receive the beam directly from the
relative Telescope Coudé Train and the calibration light from the calibration unit. On the other side the FEU feeds the
fibers that carry the light to the spectrograph, corresponding in number and size to the scientific observing modes
conceived for Espresso. The selection is made through a Toggling Unit. Purpose of the Front/End is to provide the
needed connection between the input signal, i.e. Object light, Sky light, Calibration light, and the given output fiber in
any of the foreseen observing modes.
ESPRESSO is the next generation European exoplanet hunter, combining the efficiency of a modern echelle
spectrograph with extreme radial velocity and spectroscopic precision. The instrumental radial velocity precision will be
improved to reach 10 cm/s level, to achieve a gain of two magnitudes with respect to its predecessor HARPS.
The fiber-fed, non-rotating instrument will be installed in the Combined Coudé Laboratory of the VLT (Very Large
Telescope), which is situated in the Paranal Observatory (Chile).
The main challenge in the design of the optical mounts of the instrument has been the extreme long-term stability of big
rectangular optical components in a seismic environment.
This paper describes the requirements and the adopted solution for the opto-mechanical design of the collimator mirrors,
dichroic lens, field lens and cross dispersers of the instrument.
ESPRESSO is a fibre-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO
to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope),
and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest
stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT
at the Combined Coudé Laboratory (CCL), fed by four Coudé Trains, which brings the light from the Nasmyth platforms
of the four VLT Unit Telescopes to the CCL. ESPRESSO will combine the efficiency of modern echelle spectrograph
with extreme radial-velocity precision. It will achieve a gain of two magnitudes with respect to its predecessor HARPS,
and the instrumental radial-velocity precision will be improved to reach cm/s level. Thanks to its ability of combining
incoherently the light of the 4 UTs, ESPRESSO will offer new possibilities in various fields of astronomy. The Coudé
Train is composed of a set of prisms, mirrors and lenses to deliver a pupil and an image in the CCL, including an
Atmospheric Dispersion Compensator. The use of mainly refractive optics, and Total Internal Reflection, has the
advantage of the inherent higher throughput, especially in the blue region of the spectrum.
In this paper, we present the design of the Coudé Train, the evolution of the concept towards the manufacturing phase, its
main characteristics and performances, and detail its subsystems: optical, mechanical and control electronics and
software.
ESPRESSO is an ultra-stable fiber-fed spectrograph designed to combine incoherently the light coming from up to 4 Unit Telescopes of the ESO VLT. From the Nasmyth focus of each telescope the light, through an optical path, is fed by the Coudé Train subsystems to the Front End Unit placed in the Combined Coudé Laboratory. The Front End is composed by one arm for each telescope and its task is to convey the incoming light, after a calibration process, into the spectrograph fibers. To perform these operations a large number of functions are foreseen, like motorized stages, lamps, digital and analog sensors that, coupled with dedicated Technical CCDs (two per arms), allow to stabilize the incoming beam up to the level needed to exploit the ESPRESSO scientific requirements. The Instrument Control Electronics goal is to properly control all the functions in the Combined Coudé Laboratory and the spectrograph itself. It is fully based on a distributed PLC architecture, abandoning in this way the VME-based technology previously adopted for the ESO VLT instruments. In this paper we will describe the ESPRESSO Instrument Control Electronics architecture, focusing on the distributed layout and its interfaces with the other ESPRESSO subsystems.
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 are developing a 2048x1080 Digital-Micromirror-Device-based (DMD) 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 field of view (FOV) is 6.8 arcmin x 3.6 arcmin with a plate scale of 0.2 arcsec per
micromirror. The wavelength range is in the visible and the spectral resolution is R=560 for 1 arcsec object (typical slit
size). The two arms will have 2k x 4k CCD detectors.
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
and spectra have been obtained and measured: typical spot diameters are within 1.5 detector pixels, and spectra generated
by one micro-mirror slits are displayed with this optical quality over the whole visible wavelength range. Observation
strategies are 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 mid-2015.
KEYWORDS: Prisms, Clocks, Tolerancing, Silica, Optics manufacturing, Assembly tolerances, Prototyping, Manufacturing, Control systems, Chemical elements
The multiprism device is a crucial component of the Espresso Anamorphic pupil Slicer (APSU). At the end of the slicer,
is necessary to differently fold each field to correctly illuminate the echelle. The solution is made by gluing cylindrical
prisms with proper bending low angle onto a support double plate silica window. We present here the integrated robotic
system conceived to reach the required tolerances in term of alignment and Integration. It consist in a tip tilt stage to
select the folding angle, coupled to an x-y stage to position the elements and a z axis to perform the gluing.
Keywords: Extra-solar Planet Atmospheres, High Resolution Spectroscopy, Espresso, front End
A particular example of meter class flat mirrors is the adaptive M4 Unit of E-ELT, a deformable six petals mirror of 2.4m in diameter. We studied different approaches to the calibration and certification of M4, in a trade-off between stitching and full aperture measurements. Possibilities to test the mirror with a macro-stitching concept, both in normal and grazing incidence have been considered. Approaches reported in the literature, as the Ritchey-Common or the external Fizeau, and different beam expander setups, varying the collimating mirror and the nulling system, both on-axis and off-axis, have been deeply studied to understand performances and sensitivities to fabrication errors, alignment errors and environmental effects.
We designed the interferometric test of a 300 mm flat mirror, based onto a spherical mirror and a dedicated CGH. The spherical beam of the interferometer is quasi collimated to the desired diameter by the spherical mirror, used slightly off-axis, and the CGH performs the residual wavefront correction. We performed tests on a 200 mm and 300 mm flat mirrors, and compared the results to the ones obtained by stitching, showing an accuracy well within the designed value. The possibility to calibrate the cavity by subtracting out the figure errors of the spherical mirror has also been evaluated.
ESPRESSO is the next generation ground based European exoplanets hunter. It will combine the efficiency of modern
echelle spectrograph with extreme radial-velocity and spectroscopic precision. It will be installed at Paranal's VLT in
order to achieve two magnitudes gain with respect to its predecessor HARPS, and the instrumental radial-velocity
precision will be improved to reach 10 cm/s level. We have constituted a Consortium of astronomical research institutes
to fund, design and build ESPRESSO on behalf of and in collaboration with ESO, the European Southern Observatory.
The spectrograph will be installed at the Combined Coudé Laboratory (CCL) of the VLT, it will be linked to the four 8.2
meters Unit Telescopes through four optical "Coudé trains" and will be operated either with a single telescope or with up
to four UTs, enabling an additional 1.5 magnitude gain. Thanks to its characteristics and ability of combining
incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in many fields of astronomy. Our
main scientific objectives are, however, the search and characterization of rocky exoplanets in the habitable zone of
quiet, near-by G to M-dwarfs, and the analysis of the variability of fundamental physical constants. The project is, for
most of its workpackages, in the procurement or development phases, and the CCL infrastructure is presently under
adaptation work. In this paper, we present the scientific objectives, the capabilities of ESPRESSO, the technical solutions
for the system and its subsystems. The project aspects of this facility are also described, from the consortium and
partnership structure to the planning phases and milestones.
ESPRESSO is a fibre-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope), and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT at the Combined Coudé Laboratory (CCL), fed by four Coudé Trains, which brings the light from the Nasmyth platforms of the four VLT Unit Telescopes to the CCL. ESPRESSO will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach cm/s level. Thanks to its ability of combining incoherently the light of the 4 UTs, ESPRESSO will offer new possibilities in various fields of astronomy. The Coudé Train is composed of a set of prisms and lenses to deliver a pupil and an image in the CCL, including an Atmospheric Dispersion Compensator. In this paper, we present the optical design of the Coudé Trains, the opto-mechanical concept, the required control, the main characteristics and expected performances.
This paper presents the Espresso Anamorphic pupil Slicer (APSU) implementation. ESPRESSO, the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, will be installed on ESOs Very Large Telescope (VLT). In this work we will present the design and trade-off for the pupil slicing system introduced in order to increase the resolving power, effectively decreasing slit width. Its based onto simplified optical component that introduce large anamorphism while keeping low aberrations by means of cylindrical optics. We describe here the trade-off between slicing through two adjacent squared doublets and two achromatic prisms.
This paper presents the Espresso Exposure Meter (EM) implementation. ESPRESSO,1-3 the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, will be installed on ESOs Very Large Telescope (VLT). The light coming from the Telescope through a Coud Focus4 of all the Four Telescope Units (UTs) will be collected by the Front End Unit that provides Field and Pupil stabilisation and injects the beams into the Spectrograph fibers.5 An advanced Exposure Meter system will be used to correct Radial Velocity (RV) obtained from the scientific spectrum for the Earth relative motion. In this work we will present the perfor mance of an innovative concept for the Exposure Meter system based on a Charge Coupled Device (CCD) with a chromatic approach for the calculation of the Mean Time of Exposure (MTE). The MTE is a crucial quantity used for the correction of RV for the Earth relative motion during the exposure. In particular, splitting the light in different chromatic channels on the CCD, we will probe for potential chromatic effects on the calculation of the MTE in each channel and how they could be used in order to perform the correction of RV. The paper is accompanied by a fully described numerical analysis that keeps into view a key performance evaluation for different stellar spectral types (B to M spectral main sequence classes).
ESPRESSO is the next European exoplanets hunter. It will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will be installed at Paranal's VLT in order to achieve two magnitudes gain with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach 10 cm/s level. We have constituted a Consortium of astronomical research institutes to fund, design and build ESPRESSO on behalf of and in collaboration with ESO, the European Southern Observatory. The project has passed the final design review in May 2013. The spectrograph will be installed at the Combined Coudé Laboratory of the VLT, it will be linked to the four 8.2 meters Unit Telescopes through four optical "Coudé trains" and will be operated either with a single telescope or with up to four UTs, enabling an additional 1.5 magnitude gain. Thanks to its characteristics and ability of combining incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in many fields of astronomy. Our main scientific objectives are, however, the search and characterization of rocky exoplanets in the habitable zone of quiet, near-by G to M-dwarfs, and the analysis of the variability of fundamental physical constants. In this paper, we will present the scientific objectives, the capabilities of ESPRESSO, the technical solutions for the system and its subsystems, enlightening the main differences between ESPRESSO and its predecessors. The project aspects of this facility are also described, from the consortium and partnership structure to the planning phases and milestones.
This paper is a study on the numerical modeling and the accordance between model and experiment of the behavior of Shape Memory Alloys (SMA) used as functional devices for application in Instrumentations for Astronomy. Some NiTi alloy samples was characterized using different experimental techniques, with the purpose of obtaining the material parameters, necessary to evaluate the correspondence between the simulation and the experimental behavior of the materials. The sensibility of the computational model to the variation of this parameters for the materials was investigated as well. Opto-mechanical mounting with pseudoelastic kinematic behavior and damping of launch loads onto optical elements are feasible applications that are investigated in this paper. The practical realization of a scaled down prototype is described. The device was thought for ground-based applications and made up of four small flexures that support an optical component and was designed and modeled in order to be able to evaluate the mechanical effects of different materials. The results of numerical modeling was compared to the data obtained from the prototype. We obtained a first evaluation of the development, selection and processing of NiTi-based supports for optomechanical applications and verified the performances of a complete system as a respect to an analogous system made up using traditional materials like steels.
Next-generation infrared astronomical instrumentation for ground-based and space telescopes could be based on
MOEMS programmable slit masks for multi-object spectroscopy (MOS). This astronomical technique is used
extensively to investigate the formation and evolution of galaxies. We propose to develop a 2048x1080 DMD-based
MOS instrument to be mounted on the Galileo telescope and called BATMAN. A two-arm instrument has been designed
for providing in parallel imaging and spectroscopic capabilities. The two arms with F/4 on the DMD are mounted on a
common bench, and an upper bench supports the detectors thanks to two independent hexapods. Very good optical
quality on the DMD and the detectors will be reached.
ROBIN, a BATMAN demonstrator, has been designed, realized and integrated. It permits to determine the instrument
integration procedure, including optics and mechanics integration, alignment procedure and optical quality. First images
have been obtained and measured. A DMD pattern manager has been developed in order to generate any slit mask
according to the list of objects to be observed; spectra have been generated and measured. Observation strategies will be
studied and demonstrated for the scientific optimization strategy over the whole FOV.
BATMAN on the sky is of prime importance for characterizing the actual performance of this new family of MOS
instruments, as well as investigating the operational procedures on astronomical objects. This instrument will be placed
on the Telescopio Nazionale Galileo at the beginning of next year, in 2014.
This paper wants to address the opto-mechanical stability of the Codex instrument pending onto vibration environment. CODEX is a study for an high resolution spectrograph for the European ELT. In particular the aim of the work is a preliminary verification of the instrument performances if mounted at the E-ELT Folded Nasmith location. Hence Dynamic environment of the Coudé and the folded Nasmith locations were alternatively applied to the optical layout to verify the image performances in terms of image displacements and FWHM deformations. In addition damping strategies has been verified for the improvement of the performances.
KEYWORDS: Space operations, Calibration, System on a chip, Sensors, Control systems, Satellites, Mathematical modeling, Visible radiation, Seaborgium, Data processing
Euclid is the future ESA mission, mainly devoted to Cosmology. Like WMAP and Planck, it is a
survey mission, to be launched in 2019 and injected in orbit far away from the Earth, for a nominal
lifetime of 7 years. Euclid has two instruments on-board, the Visible Imager (VIS) and the Near-
Infrared Spectro-Photometer (NISP). The NISP instrument includes cryogenic mechanisms, active
thermal control, high-performance Data Processing Unit and requires periodic in-flight calibrations
and instrument parameters monitoring. To fully exploit the capability of the NISP, a careful control
of systematic effects is required. From previous experiments, we have built the concept of an
integrated instrument development and verification approach, where the scientific, instrument and
ground-segment expertise have strong interactions from the early phases of the project. In particular,
we discuss the strong integration of test and calibration activities with the Ground Segment, starting
from early pre-launch verification activities. We want to report here the expertise acquired by the
Euclid team in previous missions, only citing the literature for detailed reference, and indicate how it
is applied in the Euclid mission framework.
Resolving power of spectrographs for large telescopes is generally limited by the maximum dimension of the dispersion
gratings. To overcome this limit, innovative optical configurations have been designed, starting from the ideas proposed
for CODEX. By properly combining pupil slicing and anamorphic magnification, a R~63’000-210’000 spectrograph has
been designed. Many different solutions were proposed during the early design phases, and a detailed trade off study has
been carried out to improve efficiency, manufacturability, and reduce risks and costs of the preliminary designs. We
present a full description of the optical design of the spectrograph after preliminary design review, together with
expected performances.
This paper presents the Espresso Front End Guiding Algorithm. ESPRESSO, the Echelle SPectrograph for Rocky
Exoplanets and Stable Spectroscopic Observations, will be installed on ESO's Very Large Telescope (VLT). The
Front End (FE) is the subsystem that collects the light coming from the Coudè Trains of all the Four Telescope
Units (UTs), provides Field and Pupil stabilization via piezoelectric tip tilt devices and inject the beams into
the Spectrograph fibers. The field and pupil guiding is obtained through a re-imaging system that elaborates
the halo of the light out of the Injection Fiber and a telescope pupil beacon. The first guiding algorithm that we
evaluated splits the FP in four areas and computes the sum of the photon counting of each pixel in that area.
The unbalancing of the photon sums will give the centroid misalignment information that will be handled by the
Instrument Control Software (ICS). Different algorithms and controllers architectures have been evaluated and
implemented in order to select a strategy that enables the FE to guide up to 20 apparent magnitude in V band.
ESPRESSO is a fiber-fed cross-dispersed echelle spectrograph which can be operated with one or up to 4 UT (Unit
Telescope) of ESO's Very Large Telescope (VLT). It will be located in the Combined-Coudé Laboratory (CCL) of the
VLT and it will be the first permanent instrument using a 16-m equivalent telescope. The ESPRESSO control software
and electronics are in charge of the control of all instrument subsystems: the four Coudé Trains (one for each UT), the
front-end and the fiber-fed spectrograph itself contained within a vacuum vessel. The spectrograph is installed inside a
series of thermal enclosures following an onion-shell principle with increasing temperature stability from outside to
inside. The proposed electronics architecture will use the OPC Unified Architecture (OPC UA) as a standard layer to
communicate with PLCs (Programmable Logical Controller), replacing the old Instrument Local Control Units (LCUs)
for ESO instruments based on VME technology. The instrument control software will be based on the VLT Control
Software package and will use the IC0 Field Bus extension for the control of the instrument hardware. In this paper we
present the ESPRESSO software architectural design proposed at the Preliminary Design Review as well as the control
electronics architecture.
This paper presents the Espresso Front End mechanical and optical conguration. ESPRESSO, Echelle SPectro-graph for Rocky Exoplanets and Stable Spectroscopic Observations, will combine the efficiency of modern echelle
spectrograph design with extreme radial-velocity precision. It will be installed on ESO's VLT and it is expected
to achieve a gain of two magnitudes with respect to its predecessor HARPS. The instrumental radial-velocity
precision will also be improved to reach cm/s level. The Front End is a modular subsystem that collects the
light coming from the Coude Trains of all the Four Telescope Units (UT), provides Field and Pupil stabilization
via piezoelectric tip tilt devices and inject the beam into the Spectrograph fiber. The Front End will also inject
the calibration light coming from the calibration unit. There will be four Front End modules, one per UT.
A rotary Stage will provide the toggling between different observation mode: Single UT Ultra High resolution
(SUT-UHR), Single UT High resolution (SUT-HR) and multiple UTS Mid Rsolution (MUT-MR). The field and
pupil guiding is obtained through a reimaging system that elaborates the halo of the light out of the Injection
Fiber and a telescope pupil beacon. A dedicated guiding algorithm has been studied in order to provide proper
image stability even with faint objects (mv=20).
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.
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 Coudé Laboratory" of the
VLT, it will be linked to the four 8.2 meters Unit Telescopes (UT) through four optical "Coudé 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.
This paper presents the GWA and the Compensating mechanism of the Near Infrared SpectroPhotometer (NISP) instrument of the ESA Euclid mission. The NIS instrument should perform an exposure sequence in the wave length range [0.9 - 2.0Jum with different exposures of the same field of views with different passband grisms with two orthogonal dispersion directions and two wavelength range. These functionalities will be achieved by a mechanism supporting the optical elements: the Grism Wheel Assembly (GWA). The required positioning repeatability is in the order of few arcsec to keep the spectra aligned with the detector pixel columns/rows. The GWA will be assembled to the NISP Optomechanical Assembly (NIOMA) with an operating temperature of 140K. A further mechanism is necessary to compensate the torque perturbances induced by the two large wheels. It is based onto a stepper motor that will drive a flywheel.
KEYWORDS: Calibration, Sensors, Interfaces, Data archive systems, Space operations, Satellites, Device simulation, Control systems, Data storage, Data acquisition
The Near Infrared Spectro-Photometer (NISP) on board the Euclid ESA mission will be developed and tested at various
levels of integration using various test equipment which shall be designed and procured through a collaborative and
coordinated effort.
In this paper we describe the Electrical Ground Support Equipment (EGSE) which shall be required to support the
assembly, integration, verification and testing (AIV/AIT) and calibration activities at instrument level before delivery to
ESA, and at satellite level, when the NISP instrument is mounted on the spacecraft.
We present the EGSE conceptual design as defined in order to be compliant with the AIV/AIT and calibration
requirements. The proposed concept is aimed at maximizing the re-use in the EGSE configuration of the Test Equipment
developed for subsystem level activities, as well as, at allowing a smooth transition from instrument level to satellite
level, and, possibly, at Ground Segment level.
This paper mainly reports the technical status at the end of the Definition phase and it is presented on behalf of the
Euclid Consortium.
In this paper we describe the thermal architecture of the Near Infrared Spectro-Photometer (NISP) on board the Euclid
ESA mission.
The instrument thermal design is based on the combination of two passive radiators coupled to cold space that, exploiting
the beneficial conditions of the L2 thermal environment, provide the temperature references for the main sub-systems.
One radiator serves as a 135K heat sink for the opto-mechanical structure and for the front-end cold electronics, while
working as an interception stage for the conductive parasitic heat leaks through struts and harness. The second, colder,
radiator provides a 95K reference for the instrument detectors. The thermal configuration has to ensure the units optimal
operating temperature needed to maximize instrument performance, adopting solutions consistent with the mechanical
specifications. At the same time the design has to be compliant with the stringent requirements on thermal stability of the
optical and detector units. The periodical perturbation of filter and grism wheel mechanisms together with orbital
variations and active loads instabilities make the temperature control one of the most critical issues of the whole design.
We report here the general thermal architecture at the end of the Definition Phase, together with the first analysis results
and preliminary performance predictions in terms of steady state and transient behavior. This paper is presented on
behalf of the Euclid Consortium.
KEYWORDS: Sensors, Computer simulations, Spectroscopy, Nondestructive evaluation, Signal processing, Data modeling, Image compression, Photometry, Data processing, Data compression
NISP is the near IR spectrophotometer instrument part of the Cosmic Vision Euclid mission. In this paper we describe an
end-to-end simulation scheme developed in the framework of the NISP design study to cover the expected focal-plane
on-board pre-processing operations. Non-destructive detector readouts are simulated for a number of different readout
strategies, taking into account scientific and calibration observations; resulting frames are passed through a series of
steps emulating the foreseen on-board pipeline, then compressed to give the final result. In order to verify final frame
quality and resulting computational and memory load, we tested this architecture on a number of hardware platforms
similar to those possible for the final NISP computing unit. Here we give the results of the latest tests. This paper mainly
reports the technical status at the end of the Definition Phase and it is presented on behalf of the Euclid Consortium.
The Euclid mission objective is to map the geometry of the dark Universe by investigating the distance-redshift
relationship and the evolution of cosmic structures. The NISP (Near Infrared Spectro-Photometer) is one of the two
Euclid instruments operating in the near-IR spectral region (0.9-2μm). The instrument is composed of:
- a cold (140K) optomechanical subsystem constituted by a SiC structure, an optical assembly, a filter wheel
mechanism, a grism wheel mechanism, a calibration unit and a thermal control
- a detection subsystem based on a mosaic of 16 Teledyne HAWAII2RG 2.4μm. The detection subsystem is
mounted on the optomechanical subsystem structure
- a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an
instrument control unit.
This presentation will describe the architecture of the instrument, the expected performance and the technological key
challenges. This paper is presented on behalf of the Euclid Consortium.
This paper want to show an innovative amateur oriented telescope with an unconventional alt-alt conguration.
The goal is to make a telescope with good optical quality reducing production costs by adopting a gimbal
based mounting to develop an alt-alt conguration suitable for a telescope. Reduce costs while preserving the
optical quality is a necessary condition to allow small groups of amateur astronomers, schools and cultural
clubs, with reduced economic resources, to acquire an astronomical instrument that encourages learning and
advancing astrophysical knowledge. This unconventional mechanism for the realization of a telescope alt-alt
provides signicant advantages. The traditional rotary motors coupled with expensive precision bearings are
replaced with two simple linear actuators coupled to a properly preloaded gimbal joint and the cell becomes the
primary structure of the telescope. A second advantage would be secured by mechanical simplicity evident in
the easy portability of the instrument. The frame alt-alt has some limitations on the horizon pointing but does
not show the zenith blind spot of the alt-az mount. A dedicated alt-alt pointing and tracking model is under
development to be compatible with commercial telescope softwares and with the proposed new mounting.
ESPRESSO is a fiber-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO
to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope),
and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest
stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT
at the Combined Coudé Laboratory (CCL), fed by four Coudé Trains, which brings the light from the Nasmyth platforms
of the four VLT Unit Telescopes to the CCL. A previous trade-off analysis, considering the use of mirrors, prisms, lenses
or fibers and several possible combinations of them, pointed towards a Full Optics solution, using only conventional
optics to launch the light from the telescope into the front-end unit. In this case, the system is composed of a set of
prisms and lenses to deliver a pupil and an image in the CCL, including an Atmospheric Dispersion Compensator. In this
paper, we present the optical design of the Coudé Trains, the opto-mechanical concept, the main characteristics and
expected performances.
Volume phase holographic gratings (VPHGs) are dispersing elements widely used in astronomical instrumentation
thanks to some unique features (for example, the peak efficiency can reach 95%). The introduction of a slant angle to the
fringes allow an increased versatility of these elements. The efficiencies of some samples produced by Kaiser Optical
Systems Inc. are reported and discussed. Moreover, some cases of interest in the astronomical field are reported.
Green sensitive photopolymers have been studied to produce volume phase gratings (VPHGs) to be used as dispersing
elements in astronomical instrumentations. They have been characterized determining the parameters that affect the
diffraction efficiency (thickness, refractive index modulation, exposure, line density, etc.). Different prototypes have
been produced varying all the selected parameters. The optical proprieties of the devices were investigated to understand
the quality of the gratings. The results were encouraging, therefore, to experience the possibility to produce a VPHG for
astronomical applications, low dispersion prototype has been designed, and it will be mounted in the AFOSC camera
(Asiago, Italy).
A volume phase holographic grating (VPHG) achieves very high diffraction efficiency up to 100% for S or P polarized
light at the first diffraction order. However, diffraction efficiency of the VPHG for non-polarized light becomes low
according as Bragg angle becomes large, and bandwidth of diffraction efficiency becomes narrow according as refractive
index modulation of grating lattice becomes small. A volume binary grating with rectangular lattice, consists of high and
low refractive index media with large or small duty ratio, is able to achieve very high efficiency nearly 100% and a wide
band width for both S and P polarization light. We have successfully fabricated germanium immersion gratings of step
groove shape with resolving power of 45,000 at 10 micron by using a nano-precision 3D grinding machine and ELID
(ELectrolytic In-process Dressing) method. However, the method requires a large amount of machine times and efforts.
We had proposed a novel immersion grating with slot shape lattice of total reflection mirrors, which achieves high
performance and lower fabrication cost. We describe the photolithography and the latest plasma nano-technologies for
fabrications of the novel diffraction gratings in our presentation. We also introduce birefringence volume gratings in this
article.
This paper wants to illustrate possible applications of Shape Memory Alloy (SMA) as functional devices for space
and ground based application in Instrumentations for Astronomy. Thermal activated Shape Memory Alloys are
materials able to recover their original shape, after an external deformation, if heated above a characteristic
temperature. If the recovery of the shape is completely or partially prevented by the presence of constraints, the
material can generate recovery stress. Thanks to this feature, these materials can be positively exploited in Smart
Structures if properly embedded into host materials. Some technological processes developed for an ecient use
of SMA-based actuators embedded in smart structures tailored to astronomical instrumentation will be presented
here. Some possible modeling approaches of the actuators behavior will be addressed taking into account trade-
offs between detailed analysis and overall performance prediction as a function of the computational time. The
Material characterization procedure adopted for the constitutive laws implementation will be described as well.
Deformable composite mirrors,1 opto-mechanical mounting with superelastic kinematic behavior and damping
of launch loads onto optical element2 are feasible applications that will be deeply investigated in this paper.
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.
Liquid photopolymers produced by Polygrama-Lynx (SM-532TR and SM-532TRF) have been studied to determine their
performances in terms of refractive index modulation, transparency and overall optical quality. Volume phase
holographic gratings (VPHGs) based on these materials have been obtained using a 532 DPSS laser and the grating
efficiency has been measured at different angles and wavelengths. Using the Kogelnik model and/or the RCWA
approach, the thickness and the refractive index modulation has been determined for gratings as function of light
exposure, line density, etc. Index modulations up to 0.03 together with good optical quality were obtained.
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.
The Euclid mission proposed in the context of the ESA Cosmic Vision program is aimed to study the challenging
problem of the Dark Energy, responsible of the acceleration of the Universe. One of the three probes of Euclid is
dedicated to study the Baryonic Acoustic Oscillations by means of spectroscopic observations of millions of galaxies in
the Near Infrared. One option for the Euclid Near Infrared Spectrograph (ENIS) is a multi-slit approach based on Digital
Micromirror Device (DMD) used as reconfigurable slit mask. The Texas Instrument 2048*1080 DMD with 13.68
micrometers pitch has been chosen. ENIS optical design is composed of four arms each using one DMD to cover a total
FOV of 0.48 square degree. The fore-optic design has to cope with the difficult task of having simultaneously a fast
beam (F/2.7) and a quasi-diffraction limited image on a 24 deg tilted plane. The compact three mirrors spectrograph is
using a grism in convergent beam for simplicity and compactness purposes. From the optical design, the mechanical
structure is based on a common carbon honeycomb bench to reach the challenging requirements of volume and mass.
KEYWORDS: Calibration, Data archive systems, Interfaces, Cameras, Staring arrays, Device simulation, Near infrared, Collimators, Data acquisition, Control systems
Euclid is a high-precision survey mission to map the geometry of the Dark Universe. The Euclid Mission concept
presented in the Assessment Phase Study Report1 was selected by ESA on February 2010 to undergo a competitive
Definition Phase. Euclid is a candidate for launch in the first slice of the Cosmic Vision Plan (M1/M2), with a possible
launch date of 2018. In this paper we refer to the instrument baseline configuration identified in the Assessment Phase. It
consisted of a Korsch telescope with a primary mirror of 1.2 m diameter and a focal plane hosting 3 scientific
instruments, each with a field of view of 0.5 deg2: (1) E-VIS: a CCD based optical imaging channel, (2) E-NIP: a NIR
imaging photometry channel, and (3) E-NIS: a NIR slitless spectral channel. We present the conceptual design developed
in the Assessment Phase study for the Ground Support Equipment required to support the assembly, integration and
verification operations at instrument level for the E-NIS baseline configuration, with particular regards to the scientific
and calibration activities.
The Euclid Near-Infrared Spectrometer (E-NIS) Instrument was conceived as the spectroscopic probe on-board the ESA
Dark Energy Mission Euclid. Together with the Euclid Imaging Channel (EIC) in its Visible (VIS) and Near Infrared
(NIP) declinations, NIS formed part of the Euclid Mission Concept derived in assessment phase and submitted to the
Cosmic Vision Down-selection process from which emerged selected and with extremely high ranking. The Definition
phase, started a few months ago, is currently examining a substantial re-arrangement of the payload configuration due to
technical and programmatic aspects. This paper presents the general lines of the assessment phase payload concept on
which the positive down-selection judgments have been based.
Deformable mirrors actuated by smart structures are promising devices for next generation astronomical instrumentation.
Thermal activated Shape Memory Alloys are materials able to recover their original shape, after an
external deformation, if heated above a characteristic temperature. If the recovery of the shape is completely
or partially prevented by the presence of constraints, the material can generate recovery stress. Thanks to this
feature, these materials can be positively exploited in Smart Structures if properly embedded into host materials.
This paper will show the technological processes developed for an efficient use of SMA-based actuators embedded
in smart structures tailored to astronomical instrumentation. In particular the analysis of the interface with the
host material. Some possible modeling approaches to the actuators behavior will be addressed taking into account
trade-offs between detailed analysis and overall performance prediction as a function of the computational
time. We developed a combined Finite Element and Raytracing analysis devoted to a parametric performance
predictions of a SMA based substrate applicable to deformable mirrors. We took in detail into account the possibility
to change the focal length of the mirror keeping a satisfactory image quality. Finally a possible approach
with some preliminary results for an efficient control system for the strongly non-linear SMA actuators will be
presented.
Deformable mirrors actuated by smart structures are promising devices for next generation astronomical instrumentation.
The piezo technology and in particular piezoceramics is currently among the most investigated
structural materials. Fragility makes Ceramic materials extremely vulnerable to accidental breakage during bonding
and embedding processes and limits the ability to comply to curved surfaces (typical of mirrors). Moreover
lead-based piezoceramics typically have relevant additional masses. To overcome these limitations, we studied
the applicability of composites piezoceramics actuators to smart structures with these purposes. We developed
a combined Finite Element and Raytracing analysis devoted to a parametric performance predictions of a smart
Piezocomposites based substrate applicable to deformable mirrors. We took in detail into account the possibility
to change the focal length of the mirror keeping a satisfactory image quality. In this paper we present a specific
type of Piezocomposite actuators and numerical/experimental techniques purposely developed to integrate them
into smart structures. We evaluated numerical and experimental results comparing bonding and embedding of
these devices.
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.
The first purpose of ESPRESSO is to develop a competitive, innovative high-resolution spectrograph to fully exploit the
potentiality of the Very Large Telescope (VLT) of the European Southern Observatory and to allow new science. It is
thus important to develop the VLT array concept bearing in mind the need to obtain the highest stability, while
preserving an excellent efficiency. This high-resolution ultra-stable spectrograph will be installed at the VLT Combined
Coudé Laboratory. A Coudé Train carries the light from the Nasmyth platforms to the Combined Coudé Laboratory,
where it feeds the spectrograph. Several concepts can be envisaged for the Coudé Train depending on the use of mirrors,
prisms and lenses or fibers or any of the possible combinations of these elements. Three concepts were selected for
analysis, one based on purely optical components and two other using fibers (with different lengths). These concepts
have different characteristics in terms of efficiency, stability, complexity, and cost. The selection of the baseline concept
took into account all these issues. In this paper, we present for each concept the optical setups, their opto-mechanical
implementation and analyze the expected throughput efficiency budget, and we also detail the current baseline concept.
High resolution spectroscopy demands detector operation in an extremely stable mechanical and thermal environment;
any tiny perturbation may affect the location of the detected spectral lines, affecting the instrument global performance.
The detector stability has been identified currently as one of the limiting factors to improve radial velocity measurements
accuracy, at the sub m/s level, and an activity focused in the performance understanding of the detector system and how
to improve those has been developed. HARPS detector system has been adopted as baseline and the results obtained in a
test campaign are described; next activities in the development to improve detector system performance are highlighted,
concluding with the information gathered for setting up radial velocity error budgets for the next generation of ESO high
stability and high resolution spectrographs.
ESPRESSO is a high-resolution, highly stable spectrograph for the VLT. It will inherit and enhance most capabilities
from HARPS and UVES, combining both stability and efficiency. The main science driver will be the detection and
characterization of Earth-like planets, but many additional science cases will benefit from its highly stable spectroscopic
observations. The facility will be installed at the combined Coudé focus of the VLT and may be linked with any of the
four UT telescopes, enabling thus a great flexibility for the efficient use of telescope time. This particularity makes the
interface with the VLT more complex than for an instrument fed by a single telescope. It impacts on the complexity of
the relationship between the consortium providing the instrument and ESO, the customer. The targeted high RV accuracy
requires very high performances in stability and resolution, which in turn require adequate technical solutions at several
levels. This paper describes the instrument system and subsystems, enlightening the most valuable differences between
ESPRESSO and it's predecessors, the details of the project, entering now the design phases, the ESPRESSO consortium,
composed of Italian, Portuguese, Spanish and Swiss institutes, and the relationship between the consortium and ESO.
Volume Phase Holographic Gratings (VPHGs) are dispersing elements which are finding wide spread in modern
optical instrumentations, also in the astronomical field. Since photochromic materials show a change in the
refractive index (Δn) upon photoirradiation, in principle they can be conveniently applied to produce rewritable
holographic devices for the near-IR region. Diarylethene-based photochromic films with Δn large enough to
meet the basic requirements have been obtained. Photochromic VPHGs have been written by using a custom
made holographic set-up, based on a Lloyd's mirror configuration. The efficiency of the photochromic gratings
has been measured at different wavelength in the NIR region. A theoretical model to predict the refractive index
profile as function of the substrate features has been developed. Finally, the efficiencies calculated by using the
RCWA approach have been compared with the experimental values.
CODEX is the proposed ultra-stable optical high-resolution spectrograph for the E-ELT, which will use novel Laser
Comb calibration techniques and an innovative design to open a new era for precision spectroscopy. With its unique
combination of light-collecting power and precision, CODEX will make it possible to directly measure the acceleration
of the Universe by monitoring the cosmological redshift drift of spectroscopic features at cosmological distances.
CODEX will also allow the assembly of the first sizeable sample of earth-like planets in the habitable zones of their stars
with the radial velocity technique. CODEX will take this technique to the level of cm/sec radial velocity stability - a
factor of about 20 improvement compared to current instruments. These are two of the scientific results anticipated for
CODEX, which will be complemented by a wide range of spectacular science in stellar, galactic and extra-galactic
Astronomy as well as Fundamental Physics. All the critical technology items are available or (as for the Laser Frequency
Comb) are in an advanced state of testing. CODEX is located at the E-ELT coudé focus that will cover the visible range
from 370 to 710 nm and provide a resolving power R~120000 with an aperture of 0.8 arcseconds in the sky.
In this paper we present a brief status report on the conceptual designs of the instruments and adaptive optics modules
that have been studied for the European Extremely Large Telescope (E-ELT). In parallel with the design study for the
42-m telescope, ESO launched 8 studies devoted to the proposed instruments and 2 for post-focal adaptive optics
systems. The studies were carried out in consortia of ESO member state institutes or, in two cases, by ESO in
collaboration with external institutes. All studies have now been successfully completed. The result is a powerful set of
facility instruments which promise to deliver the scientific goals of the telescope.
The aims of the individual studies were broad: to explore the scientific capabilities required to meet the E-ELT science
goals, to examine the technical feasibility of the instrument, to understand the requirements placed on the telescope
design and to develop a delivery plan. From the perspective of the observatory, these are key inputs to the development
of the proposal for the first generation E-ELT instrument suite along with the highest priority science goals and
budgetary and technical constraints. We discuss the lessons learned and some of the key results of the process.
X-shooter is the first second-generation instrument newly commissioned a the VLT. It is a high efficiency single
target intermediate resolution spectrograph covering the range 300 - 2500 nm in a single shot. We summarize
the main characteristics of the instrument and present its performances as measured during commissioning and
the first months of science operations.
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 A with a resolution of 700
- 1,000 (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.
ESPRESSO, a very high-resolution, high-efficiency, ultra-high stability, fiber-fed, cross-dispersed echelle spectrograph
located in the Combined-Coudé 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.
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.
The benefits Astronomy could gain by performing multi-slit spectroscopy in a space mission is renown. Digital
Micromirror Devices (DMD), developed for consumer applications, represent a potentially powerful solution. They are
currently studied in the context of the EUCLID project. EUCLID is a mission dedicated to the study of Dark Energy
developed under the ESA Cosmic Vision programme. EUCLID is designed with 3 instruments on-board: a Visual
Imager, an Infrared Imager and an Infrared Multi-Object Spectrograph (ENIS). ENIS is focused on the study of Baryonic
Acoustic Oscillations as the main probe, based on low-resolution spectroscopic observations of a very large number of
high-z galaxies, covering a large fraction of the whole sky. To cope with these challenging requirements, a highmultiplexing
spectrograph, coupled with a relatively small telescope (1.2m diameter) has been designed. Although the
current baseline is to perform slit-less spectroscopy, an important option to increase multiplexing rates is to use DMDs as
electronic reconfigurable slit masks. A Texas Instrument 2048x1080 Cinema DMD has been selected, and space
validation studies started, as a joint ESA-ENIS Consortium effort. Around DMD, a number of suited optical systems has
been developed to project sky sources onto the DMD surface and then, to disperse light onto IR arrays. A detailed study
started, both at system and subsystem level, to validate the initial proposal. Here, main results are shown, making clear
that the use of DMD devices has great potential in Astronomical Instrumentation.
KEYWORDS: Digital micromirror devices, Spectrographs, Space telescopes, Mirrors, Telescopes, Astronomical imaging, James Webb Space Telescope, Micromirrors, Spectroscopy, Microelectromechanical systems
A long-standing problem of astrophysical research is how to simultaneously obtain spectra of thousands of sources
randomly positioned in the field of view of a telescope. Digital Micromirror Devices, used as optical switches, provide a
most powerful solution allowing to design a new generation of instruments with unprecedented capabilities. We
illustrate the key factors (opto-mechanical, cryo-thermal, cosmic radiation environment,...) that constrain the design of
DMD-based multi-object spectrographs, with particular emphasis on the IR spectroscopic channel onboard the EUCLID
mission, currently considered by the European Space Agency for a 2017 launch date.
Our OPTICON JRA6 research line developed a 4 year study of non conventional uses of Volume Grating Holographic
Gratings (VPHG). The final results are witnessed by the construction of a bench prototype of tunable grating and a
tunable filters. This realization has all the characteristics of robustness and versatility to be worth extending its use to
existing of future FOSC camera spectrograph. The adjustable bending of the in/out-coming beam allows broadband
VPHG to exploits the superblaze efficiency curve in dispersing mode and thick grating, to act as narrow passband filter.
Volume phase holographic gratings (VPHGs) are becoming an interesting alternative to the ruled gratings in modern
astronomical instrumentation. Photochromic materials with thermal stability are good candidates for the development of
holographic optical elements and in particular for VPHGs. VPHGs based on photochromic materials can be written and
erased many times without the degradation of the material; moreover the material does not need any developing process
after the exposure, making the writing process very simple. We have already studied photochromic materials for this aim
in the framework of the JRA6 (Opticon Project, FP6) and we found that large modulations of the refractive index can be
achieved using diarylethene polymers. Going from the materials characterization to technology, substrates with larger
thickness and good optical properties are required. Herein we present the development of new technique to tailor the
thickness of the photochromic films in two ranges: 5 - 30 micron and 700 - 1000 micron. The former are suitable for the
development of broadband VPHGs, whereas the latter are suitable for narrow band tunable filters application. Details on
the optical properties of the films are reported. Finally, a holographic set-up based on an Ar+ laser has been optimized in
order to write the gratings.
The European Southern Observatory (ESO) is conducting a phase B study of a European Extremely Large Telescope (E-ELT).
The baseline concept foresees a 42m primary, 5 mirror adaptive telescope with two of the mirrors giving the
possibility of very fast correction of the atmospheric turbulence. In parallel to the telescope study, ESO is coordinating
8 studies of instruments and 2 of post-focus Adaptive Optics systems, carried out in collaboration with Institutes in the
member states. Scope of the studies, to be completed by 1Q 2010, is to demonstrate that the high priority scientific goals of
the E-ELT project can be achieved with feasible and affordable instruments. The main observing modes being considered
are: NIR wide field imaging and spectroscopy to the diffraction limit or with partial correction of the atmospheric seeing;
high spectral resolution, high stability visible spectroscopy; high contrast, diffraction limited imaging and spectroscopy; DL
mid-infrared imaging and spectroscopy. The status of the 8 current studies is presented.
BIRCAM is a near-infrared (0.8-2.5um) cryogenic camera based on a 1Kx1K HgCdTe array. It was designed for - and
is now mounted at - one of the Nasmyth foci of the fast-slewing 0.6 m BOOTES-IR telescope at the Sierra Nevada
Observatory (OSN) in Spain. The primary science mission is prompt Gamma Ray-Burst afterglow research, with an
implied demand for extremely time-efficient operation. We describe the challenges of installing a heavy camera on a
small high-speed telescope, of integrating the dithering mechanism, the filterwheel, and the array itself into a high-efficiency
instrument, the design of the software to meet the requirements.
The SPACE and DUNE proposals for the ESA Cosmic Vision 2015-2025 have been pre-selected for a Dark Energy
Mission. An assessment study was performed in the past few months resulting in a merged mission called EUCLID. The
study led to a possible concept for the mission and the payload, paving the way for the industrial studies. SPACE has
now become the EUCLID spectrograph channel (EUCLID-spectro). We will discuss its science and give a description of
the different studied optical designs. EUCLID-spectro aims to produce the largest three-dimensional map of the Universe
by taking near-IR spectra at R=400 and 0.9μm<λ<1.7μm for ~200 million galaxies at z<2 and H<22 over 20,000 deg2. It
will measure the expansion history of the Universe and the growth rate of structure using Baryonic Acoustic Oscillations,
redshift-space distortions and clusters of galaxies. It will distinguish true dark energy from a modification of Einstein's
gravity. The original design had 4 channels each re-imaging with mirrors a sub-field from the Casgrain focus onto a
Digital Micromirror Device (DMD). A prism spectrograph followed each array. This design was modified to adapt
EUCLID-spectro to a DUNE-type telescope, to reduce the number of optics and spectrographs, and add an imaging
capability. We studied grism spectrographs, especially for a slitless backup solution that have less optics but a smaller
field; we also studied compact prism and lens spectrographs, telescope corrector combined with micromirror arrays at
the Casgrain focus then eliminating the re-imaging, and TIR prisms over the arrays to help with packaging.
X-shooter is a wide band (U to K) intermediate resolution (4000-14000) single object three-arms spectrograph for
the VLT. Currently in the last phase of integration, X-shooter will see the first light at ESO Paranal as the first of the
VLT second generation instruments in the last quarter of 2008. We describe in this paper the final steps in the
integration and testing phase of the central Backbone with its key functions (including the active flexure
compensation mirrors) and of the two UV-Blue and Visible spectroscopic arms. We report on the stability results of
the preslit optics and of the spectrographs and on the remarkable efficiency which is derived from the measurements
of the optical components of the instrument.
A number of outstanding scientific problems require a high resolution, visual spectrograph at the E-ELT. Measuring the
dynamics of the universe, finding earth-like planets with radial velocity techniques, determining the chemical evolution
of the intergalactic medium and if physical constants varied in the past, all require a superior capability of measuring
exceedingly small Doppler shifts. We have started a Phase A study for CODEX at the E-ELT. We present here the
scientific cases, the requirements, the basic technical choices and trade offs, as well as a couple of design under
evaluation. We aim at a super stable instrument, capable of obtaining a radial velocity precision of 2 cm/sec over several
decades. It will be located at the coude focus. The design will make use of anamorphosis, pupil slicing, slanted VPH
gratings and a novel calibration system based on laser frequency combs. Several CODEX-related R&D activities are
running, and, in addition, a Call for Proposal for a precursor at the VLT has been issued.
"BOOTES-IR" is the extension of the BOOTES experiment, which has been operating in Southern Spain since
1998, to the near-infrared (nIR). The goal is to follow up the early stage of the gamma ray burst (GRB)
afterglow emission in the nIR, as BOOTES does already at optical wavelengths. The scientific case that drives
the BOOTES-IR performance is the study of GRBs with the support of spacecraft like HETE-2, INTEGRAL and
SWIFT (and GLAST in the future). Given that the afterglow emission in both, the nIR and the optical, in the
instances immediately following a GRB, is extremely bright (reached V = 8.9 in one case), it should be possible
to detect this prompt emission at nIR wavelengths too. Combined observations by BOOTES-IR and BOOTES-1
and BOOTES-2 since 2006 can allow for real time identification of trustworthy candidates to have a ultra-high
redshift (z > 6). It is expected that, few minutes after a GRB, the nIR magnitudes be H ~ 10-15, hence very
high quality spectra can be obtained for objects as far as z = 10 by much larger ground-based telescopes. A
significant fraction of observing time will be available for other scientific projects of interest, objects relatively
bright and variable, like Solar System objects, brown dwarfs, variable stars, planetary nebulae, compact objects
in binary systems and blazars.
Volume phase holographic gratings (VPHGs) are becoming widespread dispersing elements in the modern spectrograph.
Different materials can be used to make such gratings. We developed photochromic polymers based on a diarylethene
unit that make VPHG suitable for observations in the near infrared region (1 - 2 μm) where the materials are highly
transparent and show large modulation of the refractive index. This modulation was measured on films of different
polymers by using spectral reflectance obtaining values of the order of 10-2, These values are large enough to make
efficient VPHGs if the thickness of the films are about 25 μm. The sensitivity of the photochromic polyesters was
measured at 514 and 633 nm. Prototype of photochromic VPHGs were made by transferring a 600 l/mm pattern of a
Ronchi ruling glass slide on a photochromic polyester film (4 μm thick) by using a green laser (543 nm, 30 mW). The
grating was successfully transferred as shown by optical microscopy and by the diffraction pattern induced by a white
light.
X-shooter is a single target spectrograph for the Cassegrain focus of one of the VLT UTs where it will start to operate in
2008. The instrument covers in a single exposure the spectral range from the UV to the K' band. It is designed to
maximize the sensitivity in this spectral range through the splitting in three arms with optimized optics, coatings,
dispersive elements and detectors. It operates at intermediate resolutions (R=4000-14000, depending on wavelength and
slit width) with fixed echelle spectral format (with prism cross-dispersers) in the three arms. The project has completed
the Final Design Review in June 2006. In this status report, the overall concept is summarized and new results on the
dichroics, the active flexure compensation system, the operation modes and the expected performance are given. The
instrument is being built by a Consortium of Institutes from Denmark, France, Italy and the Netherlands in collaboration
with ESO. When in operation, its wide spectral range observing capability will be unique at very large telescopes.
X-shooter is a second generation VLT instrument currently under construction by a Consortium of Institutes from Denmark, Italy, The Netherlands, France and ESO. X-shooter is designed to acquire intermediate (5000-10000) resolution spectra of single objects in an unprecedented wide wavelength coverage (320-2500 nm). In order to maximize efficiency the beam is divided into 3 arms (UV, VIS and NIR) by a system of dichroics. X-shooter is designed for the Cassegrain focus of one VLT unit. The mechanical assembly has to provide specific solutions to maintain 3 arms within the strict tolerances required by the intermediate resolution, during the typical motions of the Cassegrain focal station. It must as well ensure the permanent co-alignment of the 3 slits and the stability of the spectral format on the focal plane of each arm, allowing long intervals between calibration exposures. The above requirements have been met via an innovative mechanical design merging passive stiffness and active control to obtain a light, accessible and functional assembly. This paper gives a description of the X-shooter mechanical assembly with main emphasis on the common "backbone" structure and the UV- and VIS spectrograph arms.
REMIR is the NIR camera of the automatic REM (Rapid Eye Mount) Telescope located at ESO-La Silla Observatory (Chile) and dedicated to monitor the afterglow of Gamma Ray Burst events. During the last two years, the REMIR camera went through a series of cryogenics problems, due to the bad functioning of the Leybold cryocooler Polar SC7. Since we were unable to reach with Leybold for a diagnosis and a solution for such failures, we were forced to change drastically the cryogenics of REMIR, going from cryocooler to LN2: we adopted an ad-hoc modified Continuous Flow Cryostat, a cryogenics system developed by ESO and extensively used in ESO instrumentation, which main characteristic is that the LN2 vessel is separated from the cryostat, allowing a greater LN2 tank, then really improving the hold time. In this paper we report the details and results of this operation.
The thinking about possible instruments for the future ELTs has just started and the current phase allows to pursue non-traditional
solutions. Following the guidelines of the Science Case for an ELT1,2 our team searched for possible
intersections with innovative technologies we currently deal with in our research. We found that Volume Phase
Holographic Gratings and advanced dichroics could be suited to design a non-traditional narrow band imager. We
propose in this paper a comparative analysis of a VPHG based and a dichroic based configurations for the imager.
KEYWORDS: Cameras, Control systems, Telescopes, Telecommunications, Imaging systems, Optical filters, Data acquisition, Space telescopes, Near infrared, Computer architecture
REMIR is the NIR camera of the automatic REM (Rapid Eye Mount) Telescope located at ESO La Silla Observatory -
Chile and dedicated to monitor the afterglow of Gamma Ray Burst events. The REMIR camera is composed by a set of
sub systems: the array controller, the cooling system, the temperature and the pressure monitors, the filter wheel
controller, the dither wedge controller. During 2005, a complete re-writing of the REMIR software control system started
in order to optimize the system performances: the new configuration will adopt a client server architecture, where a
supervisor system accepts via socket the data acquisition queries from AQUA (the acquisition data suite), manages the
several components of the camera and the communication with the telescope control system. Here we describe in
particular the philosophy adopted to realize the general control system, the sub systems and the communication
protocols.
The introduction of high efficiency Volume Phase Holographic Gratings (VPHGs) in astronomy led to a double think
about instrumentation. Old instruments await miracles and new instrumentations are in search of a different look.
Indeed the non conventional uses of dispersing elements can open new possibilities in instrumentation design.
Counterdispersing couples of VPHGs are best suitable for narrow and medium band filtering. Their easy handling and
macro movements will allow also a tunability of the filtering which promises good performances and robust control
system. Multiplication or cascades of this principle will lead to the design of complex multi-imaging instrumentations.
Also multi order spectroscopy can take advantage of VPHG smart positioning. Slanting and multilayers in their
manufacturing as well as optimized optical geometries can be exploited in order to reach high performance, large
spectral coverage spectrographs. We present here a set of concepts which can be applicated to very generation of
astronomical instrumentations.
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 Antarctic Plateau offers unique opportunities for ground-based Infrared Astronomy. AMICA (Antarctic Multiband Infrared CAmera) is an instrument designed to perform astronomical imaging from Dome-C in the near- (1 - 5 μm) and mid- (5 - 27 μm) infrared wavelength regions. The camera consists of two channels, equipped with a Raytheon InSb 256 array detector and a DRS MF-128 Si:As IBC array detector, cryocooled at 35 and 7 K respectively. Cryogenic devices will move a filter wheel and a sliding mirror, used to feed alternatively the two detectors. Fast control and readout, synchronized with the chopping secondary mirror of the telescope, will be required because of the large background expected at these wavelengths, especially beyond 10 μm. An environmental control system is needed to ensure the correct start-up, shut-down and housekeeping of the camera. The main technical challenge is represented by the extreme environmental conditions of Dome C (T about -90 °C, p around 640 mbar) and the need for a complete automatization of the overall system. AMICA will be mounted at the Nasmyth focus of the 80 cm IRAIT telescope and will perform survey-mode automatic observations of selected regions of the Southern sky. The first goal will be a direct estimate of the observational quality of this new highly promising site for Infrared Astronomy. In addition, IRAIT, equipped with AMICA, is expected to provide a significant improvement in the knowledge of fundamental astrophysical processes, such as the late stages of stellar evolution (especially AGB and post-AGB stars) and the star formation.
During the early Summer 2003, the REM telescope has been installed at La Silla, together with the near infrared camera REM-IR and the optical spectrograph. ROSS. The REM project is a fully automated instrument to follow-up Gamma Ray Burst, triggered mainly by satellites, such as HETE II, INTEGRAL, AGILE and SWIFT. REM-IR will perform high efficiency imaging of the prompt infrared afterglow of GRB and, together with the optical spectrograph ROSS, will cover simultaneously a wide wavelength range, allowing a better understanding of the intriguing scientific case of GRB.
In this paper we present the result of the commissioning phase of the near infrared camera REM-IR, lasted for an extended period of time and currently under the final fine tuning.
X-shooter is a single target spectrograph for the Cassegrain focus of one of the VLT UTs. It covers in a single exposure the spectral range from the UV to the H band with a possible extension into part of the K band. It is designed to maximize the sensitivity in this spectral range through the splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate resolutions (R=4000-14000, depending on wavelength and slit width) sufficient to address quantitatively a vast number of astrophysical applications while working in a background-limited S/N regime in the regions of the spectrum free from strong atmospheric emission and absorption lines. The small number of moving functions (and therefore instrument modes) and fixed spectral format make it easy to operate and permit a fast response. A mini-IFU unit (1.8" x 4") can be inserted in the telescope focal plane and is reformatted in a slit of 0.6"x 12" .The instrument includes atmospheric dispersion correctors in the UV and visual arms. The project foresees the development of a fully automatic data reduction package. The name of the instrument has been inspired by its capability to observe in a single shot a source of unknown flux distribution and redshift. The instrument is being built by a Consortium of Institutes from Denmark, France, Italy and the Netherlands in collaboration with ESO. When it operation, its observing capability will be unique at very large telescopes.
The REM Observatory, recently installed and commissioned at la Silla Observatory Chile, is the first moderate aperture robotic telescope able to cover simultaneously the visible-NIR (0.45-2.3 microns) wavelength range. His very fast pointing and his full robotization makes it an ideal observing facility for fast transients. The high throughput Infrared Camera and the Visible imaging spectrograph simultaneously fed by a dichroic allows to collect high S/N data in an unprecedented large spectral range on a telescope of this size. The REM observatory is an example of a versatile and agile facility necessary complement to large telescopes in fileds in which rapid response and/or target pre-screening are necessary. We give in this paper an overview of the Observatory and its performances with emphasis to the innovative technical solution adopted to reach such performances.
The use of high diffraction efficiency Volume Phase Holographic grating as central element in a spectrograph allows to consistently increase the instrumental throughput. Moreover the geometry they use allow them to be located in simplified optical designs and their manufacturing characteristics make them ideal also for the high resolution (R > 20,000) domain. VPHG are the perfect solution for high resolution spectrograph coupled with moderate collecting areas such as those of robotic telescopes nowadays distributed worldwide. We present in this paper the spectrograph, currently under construction, that will equip the REM telescope at la Silla Observatory, Chile.
Fast ground based simultaneous optical-near infrared observation of gamma-ray bursts (GRBs) is a mandatory priority to understand the physical mechanisms at work in these objects. The REM (Rapid Eye Mount) telescope, recently installed at La Silla (ESO, Chile), is an example of a new generation of small robotic telescopes having the capability to allow simultaneous optical and near infrared photometry and low resolution spectroscopy. The REM Optical Slitless Spectrograph (ROSS) is the optical instrument mounted on REM. ROSS has been attached, in one of the two Nasmyth foci, orthogonally to the optical axis and receives the optical light deflected by a beam splitter (dichroic), which leaves the infrared beam to continue along the optical axis where the infrared camera (REM-IR) is installed. Low resolution optical spectroscopy is obtained using an Amici prism mounted on the same filter wheel where are also mounted the broad-band V, R, I photometric filters. The detector head is a commercial camera hosting a Marconi 1024×1024 CCD chip.
We present INCA, a prototype of a light and versatile camera covering the 1-5 microns wavelength range designed for ground based and space application. INCA has innovative optical solution such as aspherical mirrors obtained via ion-beam ablation, a new light cryogenic concept and a new philosophy of chip controller. Co-financed at the bread board level by the Italian Space Agency (ASI) INCA has been recently characterized and is now ready for a phase 2 development.
CAOS (Catania Astrophysical Observatory Spectrograph) is a high-resolution (R~60,000), fiber fed, bench-mounted, prism cross-dispersed, white-pupil R-4 echelle spectrograph with polarimetric capabilities, for the 0.91m telescope on Mt. Etna. Wavelengths from 390 to 710 nm are covered in one-shot with a 2Kx2K 13.5 micron CCD. Inherent high efficiency of the spectrograph and optimum matching between fibers and spectrograph will allow high throughput for the overall system. This instrument will replace the existing spectrograph, with a net gain in spectral resolution (about a factor 2) and in efficiency (about a factor 10), extending current studies undertaken by Catania Astrophysical Observatory in stellar physics.
The Rapid Eye Mount (REM) telescope is an ambitious project devoted to the prompt observations, in the optical and Near Infrared (NIR), of Gamma-Ray Bursts (GRBs) whose high energy emission is mainly detected by the Swift satellite. The system is able to immediately react to a GRB alert and perform observations, data reduction and analyses, distributing GRB counterparts in a timescale of tens of seconds. Apart from GRB observations, REM can also drive autonomous observations of a variety of targets as X-ray transients, flare stars, etc. We describe here how REM can manage all these tasks robotically, taking into account environmental and scientific parameters as seeing, visibility, target priority, etc.
The observatories of tomorrow will necessarily be equipped with robotic facilities which will ease the use and allow a full time schedule optimization. Herein we present the application of organic materials with photochromic properties in astronomical spectrographs. Photochromism is the reversible transformation of the optical (in particular the color) and spectral properties of a material by suitable light. Organic photochromic materials can be cast in thin layers (tens to hundredths of microns) where a chosen pattern can be written leaving the layer with two areas showing different refractive index and absorption/transmission spectra. We used the opaque/transparent property of such photochromic materials to build rewritable focal plane mask for MOS spectroscopy. They were tested in laboratory and then sky tests were successfully carried out by using the AFOSC camera (Asiago Faint Object Spectrograph and Camera) of the 1.8 m telescope at Asiago Observatory. The results obtained are encouraging and the first MOS writing device is now in use at the astronomical observatory of Asiago.
The new possibilities offered since few years by the use of Volume Phase Holographic Gratings (VPHG) in astronomy have not yet yielded a new generation of instrumentation. New larger telescopes await their light analyzing devices and the higher throughput, higher versatility and lower cost of VPHG still do not award their position. We seems to have reached a stability in gratings manufacturing but their use resides mainly in R&D sector. Our group in Italy does not walk too far off this road and proposes a series of non-conventional uses of VPHG aside of refurbishing of classical, existing instrumentation.
AQuA (Automatic QUick Analysis) is a software designed to manage data
reduction and prompt detection of near infra-red (NIR) afterglows
of GRB triggered by the dedicated instruments onboard satellites and observed with the robotic telescope REM. NIR observations of GRBs early afterglow are of crucial importance for GRBs science, revealing even optical obscured or high redshift events. The core of the pipeline is an algorithm for automatic transient detection, based on a decision tree that is continuously upgraded through a Bayesian estimator (DecOAR). It assigns to every transient candidate different reliability coefficients and delivers an alert when a transient is found above the reliability threshold.
We report on the status of AVES, the Adaptive-optics Visual Echelle Spectrograph proposed for the secondary port of the Nasmyth Adaptive Optics System (NAOS) recently installed at the VLT. AVES is an intermediate resolution (R ≈ 16,000) high-efficiency fixed- format echelle spectrograph which operates in the spectral band 500 - 1,000 nm. In addition to a high intrinsic efficiency, comparable to that of ESI at Keck II, it takes advantage of the adaptive optics correction provided by NAOS to reduce the sky and detector contribution in background-limited observations of weak sources, thus allowing a further magnitude gain with respect to comparable non-adaptive optics spectrographs. Simulations show that the instrument will be capable of reaching a magnitude V = 22.5 at S/N > 10 in two hours, two magnitudes weaker than GIRAFFE at the same resolution and 3 magnitudes weaker than the higher resolution UVES spectrograph. Imaging and coronographic functions have also been implemented in the design. We present the results of the final design study and we dicuss the technical and operational issues related to its implementation at the VLT as a visitor instrument. We also discuss the possibility of using a scaled-up non-adaptive optics version of the same design as an element of a double- or triple-arm intermediate-resolution spectrograph for the VLT. Such an option looks attractive in the context of a high-efficiency large-bandwidth (320 - 1,500 nm) spectrograph ("fast-shooter") being considered by ESO as a 2nd-generation VLT instrument.
Filippo Zerbi, Florio Dalla Vedova, Alessandro Batocchio, Marco Canetti, Paolo Cerabolini, Giorgio Colombo, Mauro Ghigo, Ruben Mazzoleni, Giuseppe Pennestri
We present a status report of the R&D project INCA, aimed to create in a selected group of Italian SME the expertise to build high quality Infrared instrumentation for Astronomy. The INCA consortium is currently building a fully functional test NIR-camera (1-5 μm) exploring any sort of innovation in the field of optics (new materials, aspheric surfaces), mechanics/cryogenics (new concept in lens holding, light-weighted structures, cryo-pumps) and electronics (new chip controllers). The camera will be installed for testing at one of the major telescope facility available to the Italian community and its performances in true astronomical applications evaluated.
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.
KEYWORDS: Telescopes, Cameras, Optical filters, Electronics, Digital signal processing, Control systems, Sensors, Video processing, Video, Infrared radiation
We present the near infrared camera REM-IR that will operate aboard the REM telescope, intended as a fully automated instrument to follow-up Gamma Ray Burst, triggered mainly by satellites, such as HETE II, INTEGRAL, AGILE and SWIFT. REM-IR will perform high efficiency imaging of the prompt infrared afterglow of GRB and, together with the optical spectrograph ROSS, will cover simultaneously a wide wavelength range, allowing a better understanding of the intriguing scientific case of GRB. Due to the scientific and technological requirements of the REM project, some innovative solutions has been adopted in REM-IR.
Observations of the prompt afterglow of Gamma Ray Burst events are unanimously considered of paramount importance for GRB science and cosmology. Such observations at NIR wavelengths are even more promising allowing one to monitor high-z Ly-α absorbed bursts as well as events occurring in dusty star-forming regions. In these pages we present REM (Rapid Eye Mount), a fully robotized fast slewing telescope equipped with a high throughput NIR (Z, J, H, K) camera dedicated to detecting the prompt IR afterglow. REM can discover objects at extremely high redshift and trigger large telescopes to observe them. The REM telescope will simultaneously feed ROSS (REM Optical Slitless spectrograph) via a dichroic. ROSS will intensively monitor the prompt optical continuum of GRB afterglows. The synergy between the REM-IR camera and the Ross spectrograph makes REM a powerful observing tool for any kind of fast transient phenomena. Beside its ambitious scientific goals, REM is also technically challenging since it represent the first attempt to locate a NIR camera on a small telescope providing, with ROSS, unprecedented simultaneous wavelength coverage on a telescope of this size.
The need of new generation dispersing elements with higher throughput and with higher dispersion capabilities has now met a widely shared answer in the technology of Volume Phase Holographic Gratings (VPHG). Our group is increasingly involved in the design and realization of VPHGs both for edge basic research, testing different manufacturers, sizes and resolutions, and for existing instruments upgrades, letting observing astronomers to take advantage of new possibilities with higher performances in their common use instrumentations. In Asiago Observatory, we refurbished the AFOSC camera and spectrograph, whose twins are spread all over the world, from Chilean based ESO-Danish telescope, to Bologna (Italy) South Africa and China. In our laboratory we reproduced the cooled environment of infrared cameras, obtaining the first proofs of the good behavior of VPHG in future IR spectrograph designs.
In recent years the interest for integral field spectroscopy has increased consistently among the astronomical community. Larger detectors, efficient fibers, etc. made possible to record simultaneously spatial and spectral information of extended area of sky. The typical spectrograph that processes the Integral field data has a focal reducer configuration, i.e. a refractive collimator re-imaging the pupil on a dispersing element and a camera to re-image the focal plane with suitable pixel sampling. The focalreducer configuration is very common in the panorama of astronomical instrumentation. Nevertheless few of them offer an integral field mode. Via the example of d.o.lo.res, the Low Resolution Spectrograph of the Galileo National Telescope (TNG), we analyze the possibility to retrofit some of them with an Integral field unit designed and manufactured a posteriori.
The application of organic photochromic materials in astronomy is opening new possibilities which we are investigating in order to design innovative devices for future instrumentation. The photochromic property of transparent/opaque transition (although in a limited wavelength range) and the changes in intrinsic refractive index have led our studies to application in astronomic spectrographs, both as focal plane mask (for MOS application) and as dispersive elements (volume phase holographic gratings, VPHG), respectively. In both cases the possibility to write and erase devices with suitable irradiation has revealed a new perspective for non-disposable and fully customizable items for spectroscopy. Pursuing this goal we have synthesized a series of novel photochromic materials belonging to the diarylethenes. They fulfill the requirements of thermal stability and fatigue resistance necessary to build functional devices. Prototypes of high contrast focal plane mask working in the H-alpha spectral region have been manufactured and characterized both in laboratory and with the AFOSC camera at Asiago telescope (1.8 m). A custom writing robot (ARATRO) which, taking imaging frames and with the aid of interactive mask design software and ad hoc control electronics, is able to write MOS masks, has been constructed. The design of the MOS masks allow the fitting in the AFOSC slit wheel. The overall set-up is ready for the sky tests.
Thermally irreversible photochromic materials, mainly belonging to the diarylethene class, are potentially useful as optoelectronic devices. Poly-1,2-bis-(2-methyl thiophen-3-yl)perfluorocyclopentene has been studied in order to verify its possible application in astronomy for the production of re-writable focal plane masks and volume phase holographic gratings. Films of photochromic materials embedded in an amorphous polymer matrix are obtained by casting from chloroform solution. The films show a good transparency in the visible region when the photochromic molecule is in the open-ring form, while they totally absorb visible wavelength radiations when the photochrome is in the other isomeric form. The variation in refractive index between the two photochromic isomers, evaluated by UV-vis-NIR absorption spectra, is large enough to make this photochromic apt for the production of volume phase holographic gratings.
The upgrade of already existing instrumentation keeps always the flavor of a second-hand choice when an insufficient amount of financial and material resources can be allocated to a project. The advent of VPH gratings into the astronomical instrumentation scenario offers a new possibility to reach spectral resolutions and efficiencies that could not be dreamt of in existing low dispersion spectrograph. d.o.lo.res. is a spectrograph of the FOSC series, which couples imaging to spectroscopy by means of a grism that can be put in the parallel beam between collimator and camera. The recent upgrade with a 1435 gr/mm VPH of d.o.lo.res. is the final point of a study carried out in the gOlem labs at Brera Observatory. The lab is equipped with an modified spectrophotometer (mod*) which is able to measure transmission of optical elements which will be equipped for cryogenic environment. The working study lead to the design of a high resolution VPHG in the Ha spectral region for the low resolution spectrograph. An increase of the hitherto limiting resolution of 2250 up to 5150 together with an increase of global efficiency of a factor of 1.4 give the added value of a 5000 USD investment for an 'old' instrument.
The VIRMOS consortium of French and Italian Institutes is manufacturing 2 wide field imaging multi-object spectrographs for the European Southern Observatory Very Large Telescope, with emphasis on the ability to carry over spectroscopic surveys of large numbers of sources. The Visible Multi-Object Spectrograph, VIMOS, is covering the 0.37 to 1 micron wavelength domain, with a full field of view of 4 by 7 by 8 arcmin2 in imaging and MOS mode. The Near IR Multi-Object Spectrograph, NIRMOS, is covering the 0.9 to 1.8 microns wavelength range, with afield of view 4 by 6 by 8 arcmin2 in MOS mode. The spectral resolution for both instrument scan reach up to R equals 5000 for a 0.5 arcsec wide slit. Multi-slit masks are produced by a dedicated Mask Manufacturing Machine cutting through thin Invar sheets and capable of producing 4 slit masks approximately 300 by 300 mm each with approximately slits 5.7 mm long in less than one hour. Integral field spectroscopy is made possible in VIMOS by switching in the beam specially build masks fed by 6400 fibers coming form a 54 by 54 arcsec2 integral field head with a 80 by 80 array of silica micro-lenses. NIRMOS has a similar IFS unit with a field of 30 by 30 arcmin2. These instruments are designed to offer very large multiplexing capabilities. In MOS mode, about 1000 objects can be observed simultaneously with VIMOS, with a S/N equals 10 obtained on galaxies with I equals 24 in one hour, and approximately 200 objects can be observed simultaneously with NIRMOS, with a S/N equals 10 obtained don galaxies with J equals 22, H equals 20.6 in 1h at Req equals 200. We present here the status of VIMOS, currently under final integration, with expected first light in the summer 2000, together with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more than 150000 galaxies over the redshift range 0 < z < 5 will be undertaken based on 120 guaranteed nights awarded to the project.
KEYWORDS: Sensors, Mirrors, Telescopes, Contamination, Near infrared, Optical design, Optical filters, Signal to noise ratio, Optical instrument design, K band
In this paper a preliminary design for a prime focus corrector to be mounted at the Telescopio Nazionale Galileo (TNG) is presented. The telescope is located on La Palma and has a primary mirror of 3.5 m with a hyperbolic sag. Two optical designs have been considered in order to exploit detectors with 1k by 1k and 2k by 2k pixels. Each design makes use of four lenses, tow of which are aspherical. The first lens diameters are respectively, of 140 mm and 320 mm for the two kinds of detectors. For both designs the telescope pupil is deliberately not re-imaged, and therefore it will not be possible to insert a cold stop. For such a reason particular care has been dedicated to the telescope thermal background study, in order to optimize the baffling system. The optics is able to correct fields of 11 feet by 11 feet and of 60 feet by 60 feet, depending on the design. It should be considered that the particular geometry of the focal plane array mosaic does not permit a full exploitation of the entire field, being based on a combination of four detectors. The selected chips are HgCdTe manufactured by Rockwell, i.e. Hawaii I in the 1k by 1k case and Hawaii I in the 1k by 1k case and Hawaii II in the 2k by 2k case.
We present a preliminary design study for an adaptive optics visual echelle spectrograph and imager/coronograph for use as parallel instrument of the Nasmyth Adaptive Optics System (NAOS) on unit UT3 of the VLT. The spectrograph is intended for intermediate resolution spectroscopy of faint sources. It could be used for observations of late-type dwarfs in distant Galactic clusters and in galaxies of the local group as well as for spectroscopy of extra galactic objects like quasars and Lyman break galaxies down to a limiting magnitude of V equals 22.5. The implementation of an imaging gand coronograph mode increases the versatility of the instrument and its scientific objectives. The instrument takes advantage of Adaptive Optics at visible wavelengths both for imaging and spectroscopy. With NAOS at the VLT, the light concentration in these bands will be above approximately 60 percent of the flux in a 0.3 arcsec aperture for typical Paranal conditions. Simulations show that a gain of more than one magnitude with respect to compatible non-adaptive optical spectrography will be possible for sky- and/or detector limited observations. In addition, the smaller diffraction limit in the optical than in the IR will allow a significant gain in imaging and coronography as well. Finally, the instrument will allow gathering unprecedented experience on the performances of AO at visible wavelengths, which will be fundamental for further development of AO systems, in particular for very large telescopes.
We present in this paper a preliminary design of a near IR wide field imager for the prime focus of the ESO 3.6 meter telescope. Such a design was developed in response to the increasing demand in the astronomical community for a fast and efficient Near IR survey facility taking profit of the small pitch 1k2 and 2k2 Hybrid Focal Plane Arrays recently made available. The prime focus is a privileged location for high throughput instrument since it allows to design imagers with a relatively small amount of optical elements . At the prime focus however the plate scale is constrained to a narrow range of possibility by the F/number of primary mirror since the need to correct for aberrations does not leave much freedom for focal elongation. The ESO 3.6 telescope has a F/3 primary mirror. Unlike most of the new technology telescope of the same size, e.g. NTT or TNG, that have F/2.2 primaries, the longer focal length of the ESO 3.6 allows to reach plate scales of the order of about 15.2 as/mm, matching the scientific requirement for wide field NIR surveys. The Camera consist in a prime focus corrector made of 4 spherical lenses in fused silica providing a corrected field of 45 arcmin 0. The limited number of optical elements maximizes the throughput but does not allow to re-image the telescope pupil to position a cold stop. Therefore a detailed mode of the telescope thermal background has been sued to optimized the baffling system. Only a non-contiguous fraction of the corrected field is covered by 4 Rockwell HAWAII II 2k2 HgCdTe chips.
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