Paolo Spanò

ESPRESSO: the Echelle spectrograph for rocky exoplanets and stable spectroscopic observations

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 ESOs 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.

Project overview of OPTIMOS-EVE: the fibre-fed multi-object spectrograph for the E-ELT

OPTIMOS-EVE (OPTical Infrared Multi Object Spectrograph - Extreme Visual Explorer) is the fibre fed multi object spectrograph proposed for the European Extremely Large Telescope (E-ELT), planned to be operational in 2018 at Cerro Armazones (Chile). It is designed to provide a spectral resolution of 6000, 18000 or 30000, at wavelengths from 370 nm to 1.7 μm, combined with a high multiplex (>200) and a large spectral coverage. Additionally medium and large IFUs are available. The system consists of three main modules: a fibre positioning system, fibres and a spectrograph. The recently finished OPTIMOS-EVE Phase-A study, carried out within the framework of the ESO E-ELT instrumentation studies, has been performed by an international consortium consisting of institutes from France, Netherlands, United Kingdom and Italy. All three main science themes of the E-ELT are covered by this instrument: Planets and Stars; Stars and Galaxies; Galaxies and Cosmology. This paper gives an overview of the OPTIMOS-EVE project, describing the science cases, top level requirements, the overall technical concept and the project management approach. It includes a description of the consortium, highlights of the science drivers and resulting science requirements, an overview of the instrument design and telescope interfaces, the operational concept, expected performance, work breakdown and management structure for the construction of the instrument, cost and schedule.

The field stabilization and adaptive optics mirrors for the European Extremaly Large Telescope

A 42 meters telescope does require adaptive optics to provide few milli arcseconds resolution images. In the current design of the E-ELT, M4 provides adaptive correction while M5 is the field stabilization mirror. Both mirrors have an essential role in the E-ELT telescope strategy since they do not only correct for atmospheric turbulence but have also to cancel part of telescope wind shaking and static aberrations. Both mirrors specifications have been defined to avoid requesting over constrained requirements in term of stroke, speed and guide stars magnitude. Technical specifications and technological issues are discussed in this article. Critical aspects and roadmap to assess the feasibility of such mirrors are outlined.

CODEX: the high-resolution visual spectrograph for the E-ELT

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.

ESPRESSO: A High Resolution Spectrograph for the Combined Coudé Focus of the VLT

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

Offspring of SPACE: the spectrograph channel of the ESA Dark Energy Mission EUCLID

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 Einsteins 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.

Optical design of the ESPRESSO spectrograph at VLT

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.

Optical design of CAOS: a high-resolution spectropolarimeter for the Catania Astrophysical Observatory 0.91-m telescope

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.

An MCAO test bench for NFIRAOS

At NRC Herzberg - Astronomy we are developing a closed-loop multi-conjugate adaptive optics bench to simulate a scaled-down version of NFIRAOS, the first light MCAO system on the Thirty Meter Telescope. The current bench consists of four laser guide stars, an evenly spaced array of natural guide stars, two magnetic deformable mirrors, a Shack-Hartmann wavefront sensor and a science camera at the focal plane for the evaluation of the performance and the tip-tilt measurements. Three phase screens conjugated at different altitudes simulate the atmospheric perturbation over the telescope. We can recreate the spot elongation on the SHWFS by defocusing the ground DM and at the same time modulating the intensity of the LGS spots in order to simulate the timevarying density profile of the sodium layer. The goals of this experiment are to compare the experimental performance on the bench with the predicted results of NFIRAOS models and to test the robustness of the tomographic reconstruction under conditions including the use of faint guide stars, non-uniform density profiles of the sodium layer and known non-common path aberrations. In this paper we present an update on the status of the bench and some first results.

Pyramid versus Shack-Hartmann: Trade Study Results for the NFIRAOS NGS WFS - eScholarship

NFIRAOS, the first light AO system for the Thirty Meter Telescope, will include a natural guide star (NGS) pyramidwave-front sensor (PWFS). This WFS will have two functions: (i) when there is a bright enough NGS within the sciencefield and the lasers are turned off, the PWFS will act as the fast high order WFS driving the SCAO loop (e.g. for highcontrastimaging); and (ii) when the lasers are in use and the system operates in MCAO mode, the PWFS will act as aslow truth WFS (e.g. to measure drifts in the structure of the sodium layer). The decision to select a PWFS instead of amore conventional Shack-Hartmann WFS (SHWFS) is the outcome of a detailed trade study. In this paper, wesummarize the results of this trade study. These include extensive simulation work, which shows that, in the expectedoperating conditions of NFIRAOS, the PWFS will bring significant performance improvements, including higher Strehlratio, higher limiting magnitude and lower residual speckle levels for high contrast imaging, even when the system hasto correct for significant levels of non-common path aberrations. Our simulation results also provides new insights onthe properties of the PWFSs. We also report on opto-mechanical design work, which shows that, with the PWFS, the twofunctions (i) and (ii) can actually be combined into a single optical path, thus reducing the complexity in terms ofnumber of mechanisms and optical elements. Finally, we discuss the impacts of switching to a PWFS on the otheralready designed NFIRAOS sub-systems (e.g. the real-time computer), which we have found to be very modest.