The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 deg² will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with LPNHE (CNRS, Universities Pierre et Marie Curie and Paris-Diderot) and the WINLIGHT Systems company based in Pertuis (France), are in charge of integrating and validating the performance requirements of the full spectrographs. This includes the cryostats, shutters and other mechanisms. The first spectrograph of the series of ten has been fully tested and the performance requirements verified for the following items: focus, image quality, straylight, stability, detector properties and throughput. We present the experimental setup, the test procedures and the results.
The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation probe. The KPNO Mayall telescope will deliver light to 5000 fibers feeding ten broadband spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with the WINLIGHT Systems company (Pertuis-France) has committed to integrate and validate the performance requirements of the full spectrographs, equipped with their cryostats, shutters and other mechanisms. An AIT plan has been defined and dedicated test equipment has been designed and implemented. This equipment simulates the fiber input illumination from the telescope, and offers a variety of continuum and line sources. Flux levels are adjustable and can illuminate one or several fibers along the test slit. It is fully remotely controlled and interfaced to the Instrument Control System. Specific analysis tools have also been developed to verify and monitor the performance and stability of the spectrographs. All these developments are described in details.
We have built at the Haute-Provence observatory (France) the rst diluted telescope in the world. We describe
this prototype called Carlina, made of three 25 cm mirrors separated by a maximum baseline of 10.5 m. The
three mirrors in place are already coherenced and rst light is scheduled for June-July 2012. In this article, we
will mainly describe the focal gondola. We propose to build in the near future a 100 m aperture Large Diluted
Telescope. This diluted telescope will be more sensitive than regular interferometers (Keck, VLTI, etc.), with
higher imaging capabilities. A LDT will open new elds of research in astrophysics thanks to very high angular
resolution imaging of the surface of supergiant stars, AGN, gravitational micro-lens systems, exo-planets, etc.
ELP-OA ('Etoile Laser Polychromatique pour l'Optique Adaptative) aims at demonstrating the tip-tilt is measurable
with a Laser Guide Star (LGS) without any natural guide star. This allows a full sky coverage down to
visible wavelengths. ELP-OA is being setup at Observatoire de
Haute-Provence (OHP). To create a polychromatic
LGS, we use two pulsed dye lasers (at 569nm and 589nm) to produce a two-photons excitation of sodium
atoms in the mesosphere. The chromatism of the refractive index of the air yields a difference of the LGS
direction at different wavelengths. The position differences is proportionnal to the tip-tilt. Since the LGS isn't
sharp enough to give us a small enough error in the differential
tip-tilt, we use an interferometric projector to
improve the high spatial information in the laser spot. It requires an adaptive optics working down to 330nm.
This one is done by post-processing algorithms. Two two aperture projectors are used. Each one creates a
fringe-modulated LGS, and a better RMS error in the LGS position is obtained by measuring the information
in a normal direction with respect to the fringes. By using a two aperture projector, we also strongly decrease
the negative effect of the laser star elongation in the mesosphere, and the Rayleigh contribution near the LGS.
We propose a new optimal algorithm to retrieve the tip-tilt from simultaneous images at different wavelengths.
To enhance the RMS error of the measurements, we extend this algorithm to exploit the temporal correlation
of the turbulence.
SOPHIE is a new fiber-fed echelle spectrograph in operation since October 2006 at the 1.93-m telescope of Observatoire
de Haute-Provence. Benefiting from experience acquired on HARPS (3.6-m ESO), SOPHIE was designed to obtain
accurate radial velocities (~3 m/s over several months) with much higher optical throughput than ELODIE (by a factor of
10). These enhanced capabilities have actually been achieved and have proved invaluable in asteroseismology and
exoplanetology. We present here the optical concept, a double-pass Schmidt echelle spectrograph associated with a high
efficiency coupling fiber system, and including simultaneous wavelength calibration. Stability of the projected spectrum
has been obtained by the encapsulation of the dispersive components in a constant pressure tank. The main
characteristics of the instrument are described. We also give some technical details used in reaching this high level of