ABSTRACT: 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.
Ground-based and Airborne Instrumentation for Astronomy IV; 09/2012
ABSTRACT: 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.
Ground-based and Airborne Instrumentation for Astronomy III, San Diego; 07/2010
ABSTRACT: 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.
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, San Diego; 07/2010
ABSTRACT: In the frame of the call for proposal for the E-ELT instrumentation studies, the CODEX team carried out the feasibility study
for a spectrograph for extremely stable Doppler measurements. The CODEX project and its scientific goals are described in
[L. Pasquini, S. Cristiani et al. in Messenger 122, 10 (2005)]. During the development of this study, the CODEX team recognized that a CODEX-like instrument would be of high scientific
interest also on the VLT. The ESPRESSO concept was born. The contribution by J. Liske in this volume highlights the direct
links between the two instruments (see also [J. Liske, A. Grazian, E. Vanzella et al. in 2008MNRAS.tmp..460L, in press]).
12/2008: pages 395-399;
ABSTRACT: 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.
Ground-based and Airborne Instrumentation for Astronomy II, Marseille; 07/2008
ABSTRACT: The redshifts of all cosmologically distant sources are expected to experience a small, systematic drift as a function of time due to the evolution of the Universe's expansion rate. A measurement of this effect would represent a direct and entirely model-independent determination of the expansion history of the Universe over a redshift range that is inaccessible to other methods. Here we investigate the impact of the next generation of Extremely Large Telescopes on the feasibility of detecting and characterising the cosmological redshift drift. We consider the Lyman alpha forest in the redshift range 2 < z < 5 and other absorption lines in the spectra of high redshift QSOs as the most suitable targets for a redshift drift experiment. Assuming photon-noise limited observations and using extensive Monte Carlo simulations we determine the accuracy to which the redshift drift can be measured from the Ly alpha forest as a function of signal-to-noise and redshift. Based on this relation and using the brightness and redshift distributions of known QSOs we find that a 42-m telescope is capable of unambiguously detecting the redshift drift over a period of ~20 yr using 4000 h of observing time. Such an experiment would provide independent evidence for the existence of dark energy without assuming spatial flatness, using any other cosmological constraints or making any other astrophysical assumption. Comment: Accepted for publication in MNRAS, 27 pages, 19 figures
ABSTRACT: CODEX, a high resolution, super-stable spectrograph to be fed by the E-ELT, the most powerful telescope ever conceived, will for the first time provide the possibility of directly measuring the change of the expansion rate of the Universe with time and much more, from the variability of fundamental constants to the search for other earths. A study for the implementation at the VLT of a precursor of CODEX, dubbed ESPRESSO, is presently carried out by a collaboration including ESO, IAC, INAF, IoA Cambridge and Observatoire de Geneve. The present talk is focused on the cosmological aspects of the experiment. Comment: 6 pages Latex, to appear in the proceedings of `A Century of Cosmology', S. Servolo, August 2007, to be published in Il Nuovo Cimento
ABSTRACT: Many talks in this conference have shown the power of high resolution spectroscopy, coupled to high precision. A new spectrograph,
fed by an Extremely Large Telescope, will have such a huge collecting power that it will allow for the first time some outstanding
applications. We argue here that such a new instrument should therefore aim at the highest long term stability and precision.
High resolution and high accuracy need photons; the ELTs will give us a tremendous opportunity, and we shall make use of it.
11/2007: pages 249-253;
ABSTRACT: The high-resolution spectrograph HARPS (High-Accuracy Radial-velocity Planet Searcher) will be installed on the 3.6m telescope at the ESO La Silla Observatory towards the end of 2002 and offered to the astronomical community by mid-2003. Assembly and integration of the instrument took place at the Geneva Observatory, Switzerland, during Spring 2002. At present, the verification of the system performance is in progress and is already in an advanced phase. We present in this paper the first results of our laboratory tests and describe various performance figures. We stress the outstanding mechanical and thermal stability of the instrument which are crucial for accurate radial velocity measurements. We also give a description of the simultaneous ThAr-reference technique which ensures an overall efficiency 6 times higher than with an the iodine cell absorption method. The combination of the high instrumental stability with the simultaneous ThAr-reference technique provides HARPS with characteristics highly adapted for accurate radial-velocity determination at the level of 1 m/s. These make our instrument suitable for the detection of planetary systems and of extra-solar planets with sub-saturnian mass.
Instrument Design and Performance for Optical/Infrared Ground-based Telescopes; 07/2003
ABSTRACT: By October 1st, 2003, ESO's new and unique planet-hunting machine HARPS (High-Accuracy Radial velocity Planetary Searcher) has become operational. The measurements made during the commissioning phase and the first weeks of operation are of outstanding quality. In this article we report among other examples on the first extra-solar planet discovered with HARPS and on the detection of tiny stellar oscillations. The results presented demonstrate that HARPS is currently the most precise Doppler- measurements machine in the world. With this acquisition ESO places itself at the head of a scientific domain, whose interest has continued to grow during the past years.
The Messenger. 01/2003; 114:20.
ABSTRACT: An extensive review of past, present and future research on extrasolar
planets is given in the article “Extrasolar Planets” by N.
Santos et al. in the present issue of The Messenger. Here we want to
mention only that the search for extrasolar planets and the
interpretation of the scientific results have evolved in recent years
into one of the most exciting and dynamic research topics in modern
The Messenger. 11/2002; 110:9-14.
ABSTRACT: Contents: 1. Search for extrasolar planets by precise Doppler
measurements. 2. The CORALIE spectrograph. 3. The CORALIE planet search
programme. 4. Catching the sound of stars with CORALIE. 5. HARPS: the 1
m s-1 precision instrument.
The Messenger. 08/2001; 105:1-7.
ABSTRACT: A prototype version of Meudon-ESO Fiber Optics Spectrograph (MEFOS)
tested at La Silla in January 1991 is briefly described. Computation
results which take into account telescope, fiber and spectrograph
effects show that MEFOS should be about 25 percent more efficient than
The Messenger. 08/1991; 65:54-59.
ABSTRACT: Different types of commercial fibre optics find useful application in
modern astronomical instruments. ESO has been particularly interested
in the use of fibres as "light pipes" to feed spectrographs at a
distance from the telescope. This is the case of the Coude Echelle
Spectrograph (CES) fed through a 35 m long fibre from the Cassegrain
focus of the 3.6-m telescope, alternatively to the standard use with
the CAT telescope. The gain one can achieve by using the larger
telescope can be as large as two magnitudes over a wide spectral range
and this difference opens the way to an entirely new class of
observations that at the CAT would be photon limited. Obviously,
would-be observers have to be aware that when the link operates, both
the CAT and the 3.6-m need to be "booked". As a consequence, the OPC
checks with special care whether the use of the larger collecting area
is indeed absolutely necessary. A very convincing case and an
outstanding scientific justification are a must for these programmes.
The Messenger. 11/1989; 58:58-60.
ABSTRACT: Striking differences are noted among the three contiguous lines of sight
of the present Na I interstellar line observations of the two LMC
supergiants Sk -69 deg 203 and Sk -69 deg 211, at few arcmin from SN
1987A. The Galactic components have different strengths, implying
inhomogeneities of the Galactic disk's interstellar gas on a scale of
tenths of parsecs. The main LMC absorption shows strength and radial
velocity variations between each pair of the three lines of sight,
suggesting a complex distribution of the main body of the LMC
interstellar gas in the direction of the SN.
The Astrophysical Journal 03/1989; 339:L63-L66. · 6.02 Impact Factor
ABSTRACT: The ESO fibre facility for multiobject spectroscopy at the Cassegrain
focus of the 3.6-m telescope, OPTOPUS, has been operating since March
1985. A complete description of the system is given in the ESO
Operating Manual No. 6. It is possible to observe with OPTOPUS a
maximum of 52 objects distributed over a field of 33'. Special aperture
plates are prepared in advance of the observations in the ESO workshop
from accurate alpha and delta coordinates of the selected objects.
These plates are eventually mounted at the telescope and the fibres
are manually inserted in the apertures; at the other end they form the
entrance slit of a CCD spectrograph. In the last four years OPTOPUS has
been used in 33 nights for 14 different programmes. It has always
operated with high reliability, collecting some 6,000 spectra. The
limiting magnitudes at a resolving power of about 500 in the visual are
about 18.5 for galaxies and 20 for quasars in a two-hour exposure.
While these limits allow useful work for a large number of programmes,
there are two aspects of the present system which must be considered
as unsatisfactory: the poor blue-UV transmission of the fibres and the
reduced efficiency of a number of them, mainly due to imperfect
centring of the microienses at their input ends. As the interest in
using the facility is actually increasing (see e.g., DAEC Workshop,
1988), ESO started a programme to improve the weak points while
keeping the basic conceptunchanged.
The Messenger. 02/1989; 55:62-64.
ABSTRACT: The installation at the (Coudé Echelle Spectrograph) of the new
Short Camera coupled with an efficient CCD detector and the improvements
on the spectral transmission of the commercially available fibres
prompted a new experiment. The link was established between the
Cassegrain focus of the 3.6 m and the CES. A change of fibres to take
into account variable seeing conditions or to adapt to a special
wavelength region can be accomplished in one hour. The paper deals with
the measurements of the efficiency at the telescope and presents briefly
some astronomical results.
ABSTRACT: Observations of the NAI interstellar lines of the two LMC supergiants
SK-69 203 and SK-69 211 have been obtained with the CES spectrograph
linked by fibers to the 3.6 m telescope at La Silla, ESO. Both stars are
few arcminutes from the SN1987a and, despite their proximity to the
SN1987a, a number of striking differences are present in the whole
interstellar spectrum. The variations of the Galactic components imply
dishomogeneities of the ISM in the disk on the very small scale of
tenths of parsecs. Comparison with existing data provides some evidence
that the cloud at 60 km/sec, already detected in the SN1987a spectrum,
belongs to the Galactic halo. The SN1987a feature at 220 km/sec is
absent from the spectra of the two LMC supergiants and appears as a
characteristic signature of the supernova line of sight. The LMC
absorptions appear at different velocities in the two supergiants and in
SN1987a suggesting a complex structure and motion of the IS gas in the
direction of the supernova.
Memorie della Societa Astronomica Italiana. 60:233-237.