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.
DDOTI will be a wide-field robotic imager consisting of six 28-cm telescopes with prime focus CCDs mounted on a common equatorial mount. Each telescope will have a field of view of 12 deg2, will have 2 arcsec pixels, and will reach a 10σ limiting magnitude in 60 seconds of r ≈ 18:7 in dark time and r ≈ 18:0 in bright time. The set of six will provide an instantaneous field of view of about 72 deg2. DDOTI uses commercial components almost entirely. The first DDOTI will be installed at the Observatorio Astronómico Nacional in Sierra San Pedro Martír, Baja California, México in early 2017. The main science goals of DDOTI are the localization of the optical transients associated with GRBs detected by the GBM instrument on the Fermi satellite and with gravitational-wave transients. DDOTI will also be used for studies of AGN and YSO variability and to determine the occurrence of hot Jupiters. The principal advantage of DDOTI compared to other similar projects is cost: a single DDOTI installation costs only about US$500,000. This makes it possible to contemplate a global network of DDOTI installations. Such geographic diversity would give earlier access and a higher localization rate. We are actively exploring this option.
The ASTEP program is dedicated to exo-planet transit search from the Concordia Station located at Dome C, Antarctica.
It comprises two instruments: a fixed 10cm refractor pointed toward the celestial South Pole, and a 400mm Newton
telescope with a 1x1 degree field of view. This work focuses on the latter instrument. It has been installed in November
2009, and has been observing since then during the two polar winters 2010 and 2011. After presenting the main science
observing programs, we review the telescope installation, performance, and describe its operating conditions as well as
the data reduction and handling strategy. The resulting lightcurves are generally very stable and of excellent quality, as
shown by continuous observations of WASP-19 that we present here.
The Concordia Base in Dome C, Antarctica, is an extremely promising site for photometric astronomy due to the 3-
month long night during the Antarctic winter, favorable weather conditions, and low scintillation. The ASTEP project
(Antarctic Search for Transiting ExoPlanets) is a pilot project which seeks to identify transiting planets and understand
the limits of visible photometry from this site. ASTEP 400 is an optical 40cm telescope with a field of view of 1° x 1°.
The expected photometric sensitivity is 1E-3, per hour for at least 1,000 stars. The optical design guarantees high
homogeneity of the PSF sizes in the field of view. The use of carbon fibers in the telescope structure guarantees high
stability. The focal optics and the detectors are enclosed in a thermally regulated box which withstands extremely low
temperatures. The telescope designed to run at -80°C (-110°F) was set up at Dome C during the southern summer 2009-
2010. It began its nightly observations in March 2010.
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.
We discuss our Polychromatic Laser Guide Star (PLGS) end-to-end model which relies on the 2-photon
excitation of sodium in the mesosphere. We then describe the status of the setup at Observatoire de Haute-
Provence of ELP-OA, the (PLGS) concept demonstrator. The PLGS aims at measuring the tilt from the LGS
without any NGS. Two dye laser chains locked at 589 and 569nm are required. These chains, are similar to those
of our PASS-2 experiment at Pierrelatte (1999). The two oscillators, preamplifiers and amplifiers are pumped
with NdYAGs. Both beams are phase modulated with a double sine function. If required, a third stage can
be added. It is expected that beams will deliver an output average power of 34W each, so that 22W will be
deposited into the mesosphere. If it is not enough, there is enough power supply to twofold it.
These lasers are being settled in the building of the OHP 1.52m telescope, partly at the first floor, and partly
at the top of the North pillar. Beams will propagate from there to the launch telescope attached to the 1.52m
one through a train of mirrors fixed with respect to the beam, so that incident angles are constant.
The coudé focus of the 1.52m telescope will be equipped with an adaptive optics device, closely derived from
the ONERA's BOA one. The Strehl ratio at 330nm for the differential tilt measurement channel is expected to
be 30-40% for r0 = 8 - 10cm. Telescope vibrations will be measured with pendular seismometers upgraded from Tokovinin's prototype. The full demonstrator is planned to run in 2010.
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
A particular flavor of multi-object spectrographs uses pick-off and steering mirrors. These mirrors perform target selection by relaying the optical beams from variable positions in the focal plane to fixed optics in the instrument. Examples of instrument conceptual designs based on this system are presented and illustrated. Particular emphasis is given to the beam steering mirror (BSM) environment which requires the following mechanical motions: translation, rotations and possibly active deformation of the optical surface. A BSM design featuring translation, tip-tilt and a toroidal deformable surface is presented. First results from a prototype development are also presented. A metrology system including wavefront sensing allows to measure and control the position of the optical beam. This system, required for system tests, integration, calibration and operation, is presented. This work is part of the Laboratoire d'Astrophysique de Marseille (LAM) contribution to the beam manipulation work package of the OPTICON smart focal plane.
We report on the science case high level specifications for a wide field spectrograph instrument for an Extremely Large
Telescope (ELT) and present possible concepts. Preliminary designs are presented which resort to different instrument
concepts: monolithic integral field (IFU), multi-IFU, and a smart tunable filter. This work is part of the activities performed
in the work package 'Instrumentation' of the 'ELT Design Study', a programme supported by the European Community,
Framework Programme 6.
A dedicated optimized spectrograph based on an integral field unit adopting an imager slicing concept has been
developed for the SNAP (SuperNova/Acceleration Probe) experiment. A prototype for the SNAP application is
undergoing test at Marseille (France) between LAM (INSU) and CPPM/IPNL(IN2P3) to provide the verification of the
optical performances associated with the development of a complete simulation of the instrument. The goal of this
demonstrator is to prove the optical and functional requirements of the SNAP spectrograph: diffraction losses, spectrophotometric
calibration, image quality and straylight.
We propose to implement an Integral-Field Unit (IFU) mode in the near-infrared spectrograph NIRSpec of the future James Webb Space Telescope (JWST), instrument under the responsibility of the European Space Agency (ESA). The IFU mode will provide unique additional scientific capabilities, complementary to those of the main multi-object mode of NIRSpec. It would cover a 3"x3" field of view with a 0.075" sampling and make use of the R=3000 spectral configurations of NIRSpec, covering the complete 1.0-5.0 microns range in three shots. First performance simulations yield a limiting AB magnitude of 24 for a point-like source. On the technical side, the IFU is based on the advanced image slicer concept and would include a stack of forty 900 μm thick, slicing mirrors. We are currently conducting a prototyping work funded by ESA, aiming at demonstrating a TRL6 readiness level for this technology (see presentation by F. Laurent). We present the optical design of the IFU, the strategy used during its definition (minimum impact on NIRSpec), as well as the proposed implementation within the NIRSpec instrument. We will stress that, this currently optional mode is a unique opportunity to provide JWST with a powerful integral field mode at marginal costs.
In the frame of an European Space Agency (ESA) contract, a consortium of three European research institutes (Laboratoire d'Astrophysiqu de Marseille, Centre de Recherche Astronomique de Lyon and the University of Durham) and the Cybernetix company have designed, manufactured and tested a prototype of an Integral Field Unit (IFU) for the NIRSpec instrument of the future James Webb Space Telescope (JWST). After a brief presentation of the optical design of this prototype, which is based on the advanced slicer concept, we will focus on the optical tests of this prototype. We will first present the tests peformed at LAM on the individual optical elements prior to their integration in the mechanical structure, as well as the alignment tests conducted as part of the integration procedure. We will then describe the tests and their results in the visible of the complete IFU system both at room temperature (tests performed at CRAL) and at operating temperature (30 K, tests peformed at the University of Durham). Briefly, these tests included: measurements of the characteristics (position, shape, size ...) of the pseudo-slit of the IFU prototype; measurement of the point-spread-function at different locations within its field of view; and measurement of the position, shape and size of the exit pupils. Last, we will conclude on the TRL6 readiness of the advanced image slicer technique and we will provide a glimpse of how wide-spread this technique is becoming both for ground- and space-based applications.