L. Parès

The MUSE second-generation VLT instrument

Summary: The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph currently in manufacturing, assembly and integration phase. MUSE has a field of 1x1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The instrument is a large assembly of 24 identical high performance integral field units, each one composed of an advanced image slicer, a spectrograph and a 4kx4k detector. In this paper we review the progress of the manufacturing and report the performance achieved with the first integral field unit.

SPIRou: the near-infrared spectropolarimeter/high-precision velocimeter for the Canada-France-Hawaii telescope

SPIRou is a near-IR echelle spectropolarimeter and high-precision velocimeter under construction as a next- generation instrument for the Canada-France-Hawaii-Telescope. It is designed to cover a very wide simultaneous near-IR spectral range (0.98-2.35 μm) at a resolving power of 73.5K, providing unpolarized and polarized spectra of low-mass stars at a radial velocity (RV) precision of 1m/s. The main science goals of SPIRou are the detection of habitable super-Earths around low-mass stars and the study of stellar magnetism of star at the early stages of their formation. Following a successful final design review in Spring 2014, SPIRou is now under construction and is scheduled to see first light in late 2017. We present an overview of key aspects of SPIRou’s optical and mechanical design.

Probing unexplored territories with MUSE: a second generation instrument for the VLT

The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 0.465-0.93 μm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 0.6-0.93 μm wavelength range. Although the MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, environment of young stellar objects, super massive black holes and active nuclei in nearby galaxies or massive spectroscopic surveys of stellar fields in the Milky Way and nearby galaxies.

SPIRou @ CFHT: spectrograph optical design

SPIRou is a near-infrared, echelle spectropolarimeter/velocimeter under design for the 3.6m Canada-France-Hawaii Telescope (CFHT) on Mauna Kea, Hawaii. The unique scientific capabilities and technical design features are described in the accompanying (eight) papers at this conference. In this paper we focus on the lens design of the optical spectrograph. The SPIROU spectrograph is a near infrared fiber fed double pass cross dispersed spectrograph. The cryogenic spectrograph is connected with the Cassegrain unit by the two science fibers. It is also fed by the fiber coming from the calibration box and RV reference module of the instrument. It includes 2 off-axis parabolas (1 in double pass), an echelle grating, a train of cross disperser prisms (in double pass), a flat folding mirror, a refractive camera and a detector. This paper describes the optical design of the spectrograph unit and estimates the performances. In particular, the echelle grating options are discussed as the goal grating is not available from the market.

SPIRou @ CFHT: design of the instrument control system

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a nextgeneration instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goals of detecting Earth-like planets around low-mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of eight companion papers. In this paper, the means of controlling the instrument are discussed. Most of the instrument control is fairly normal, using off-the-shelf components where possible and reusing already available code for these components. Some aspects, however, are more challenging. In particular, the paper will focus on the challenges of doing fast (50 Hz) guiding with 30 mas repeatability using the object being observed as a reference and on thermally stabilizing a large optical bench to a very high precision (~1 mK).μ

Front end of the SPIRou spectropolarimeter for Canada-France Hawaii Telescope

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a nextgeneration instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of detecting Earth-like planets around low-mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the Front End of the instrument is presented. Positioned at the Cassegrain Focal plane of the telescope, the front end is constituted of an atmospheric dispersion corrector, a field viewer with an image stabilization unit (0.03 arc seconds RMS stabilization goal), a calibration wheel and an achromatic polarimeter unit based on Fresnel Rhombs. The polarimeter permits the circular and linear polarization analysis. The retardance of the Fresnel rhombs is nominal to better than 0.5% in the whole spectral domain. The evaluation and the reduction of the thermal background of the Front end is a challenging part of the instrument.

SPIRou @ CFHT: fiber links and pupil slicer

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a next-generation instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of detecting Earth-like planets around low mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the fiber links which connects the polarimeter unit to the cryogenic spectrograph unit (35 meter apart) are described. The pupil slicer which forms a slit compatible with the spectrograph entrance specifications is also discussed in this paper. Some challenging aspects are presented. In particular this paper will focus on the manufacturing of 35 meter fibers with a very low loss attenuation (< 13dB/km) in the non-usual fiber spectral domain from 0.98 μm to 2.35 μm. Other aspects as the scrambling performance of the fiber links to reach high accuracy radial velocity measurements (1m/s) and the design of the pupil slicer exposed at a cryogenic and vacuum environment will be discussed.

MUSE Optical Alignment Procedure

MUSE (Multi Unit Spectroscopic Explorer) is a second generation VLT integral field spectrograph (1x1arcmin² Field of View) developed for the European Southern Observatory (ESO), operating in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently assembling and testing MUSE in the Integration Hall of the Observatoire de Lyon for the Preliminary Acceptance in Europe, scheduled for 2013. MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic instrument mechanical structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2011, all MUSE subsystems were integrated, aligned and tested independently in each institute. After validations, the systems were shipped to the P.I. institute at Lyon and were assembled in the Integration Hall This paper describes the end-to-end optical alignment procedure of the MUSE instrument. The design strategy, mixing an optical alignment by manufacturing (plug and play approach) and few adjustments on key components, is presented. We depict the alignment method for identifying the optical axis using several references located in pupil and image planes. All tools required to perform the global alignment between each subsystem are described. The success of this alignment approach is demonstrated by the good results for the MUSE image quality. MUSE commissioning at the VLT (Very Large Telescope) is planned for 2013.

UVMag: Space UV and visible spectropolarimetry

UVMag is a project of a space mission equipped with a high-resolution spectropolarimeter working in the UV and visible range. This M-size mission will be proposed to ESA at its M4 call. The main goal of UVMag is to measure the magnetic fields, winds and environment of all types of stars to reach a better understanding of stellar formation and evolution and of the impact of stellar environment on the surrounding planets. The groundbreaking combination of UV and visible spectropolarimetric observations will allow the scientists to study the stellar surface and its environment simultaneously. The instrumental challenge for this mission is to design a high-resolution space spectropolarimeter measuring the full- Stokes vector of the observed star in a huge spectral domain from 117 nm to 870 nm. This spectral range is the main difficulty because of the dispersion of the optical elements and of birefringence issues in the FUV. As the instrument will be launched into space, the polarimetric module has to be robust and therefore use if possible only static elements. This article presents the different design possibilities for the polarimeter at this point of the project.

The MUSE project face to face with reality

MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument built for ESO (European Southern Observatory) to be installed in Chile on the VLT (Very Large Telescope). The MUSE project is supported by a European consortium of 7 institutes. After the critical turning point of shifting from the design to the manufacturing phase, the MUSE project has now completed the realization of its different sub-systems and should finalize its global integration and test in Europe. To arrive to this point many challenges had to be overcome, many technical difficulties, non compliances or procurements delays which seemed at the time overwhelming. Now is the time to face the results of our organization, of our strategy, of our choices. Now is the time to face the reality of the MUSE instrument. During the design phase a plan was provided by the project management in order to achieve the realization of the MUSE instrument in specification, time and cost. This critical moment in the project life when the instrument takes shape and reality is the opportunity to look not only at the outcome but also to see how well we followed the original plan, what had to be changed or adapted and what should have been.