Laurent Martin

Prime focus spectrograph: Subaru's future

The Prime Focus Spectrograph (PFS) is a new multi-fiber spectrograph on Subaru telescope. PFS will cover around 1.4 degree diameter field with ~2400 fibers. To ensure precise positioning of the fibers, a metrology camera is designed to provide the fiber position information within 5 {\mu}m error. The final positioning accuracy of PFS is targeted to be better than 10 {\mu}m. The metrology camera will locate at the Cassegrain focus of Subaru telescope to cover the whole focal plane. The PFS metrology camera will also serve for the existing multi-fiber infrared spectrograph FMOS.The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project has been endorsed by Japanese community as one of the main future instruments of the Subaru 8.2-meter telescope at Mauna Kea, Hawaii. This optical/near-infrared multi-fiber spectrograph targets cosmology with galaxy surveys, Galactic archaeology, and studies of galaxy/AGN evolution. Taking advantage of Subaru’s wide field of view, which is further extended with the recently completed Wide Field Corrector, PFS will enable us to carry out multi-fiber spectroscopy of 2400 targets within 1.3 degree diameter. A microlens is attached at each fiber entrance for F-ratio transformation into a larger one so that difficulties of spectrograph design are eased. Fibers are accurately placed onto target positions by positioners, each of which consists of two stages of piezo-electric rotary motors, through iterations by using back-illuminated fiber position measurements with a widefield metrology camera. Fibers then carry light to a set of four identical fast-Schmidt spectrographs with three color arms each: the wavelength ranges from 0.38 μm to 1.3 μm will be simultaneously observed with an average resolving power of 3000. Before and during the era of extremely large telescopes, PFS will provide the unique capability of obtaining spectra of 2400 cosmological/astrophysical targets simultaneously with an 8-10 meter class telescope. The PFS collaboration, led by IPMU, consists of USP/LNA in Brazil, Caltech/JPL, Princeton, and JHU in USA, LAM in France, ASIAA in Taiwan, and NAOJ/Subaru.

Normal Frequencies of the C677T Genotypes on the Methylenetetrahydrofolate Reductase (MTHFR) Gene Among Lymphoproliferative Disorders but not in Multiple Myeloma

The folate availability seems to he critical for the DNA integrity since it is required for the transfer of methyl groups in the biosynthesis of thymidilate. Although the excessive incorporation of uracils to the DNA can be efficiently removed. this mechanism of reparation produces many double-strand breaks from two opposing nicks. Several chromosomal abnormalities (mainly translocations and deletions perhaps not well understood) are involved in the origin of lymphoproliferative disorders. The TT homozygosity at nucleotide 677 in the gene of methylene letrahydrofolatereductase (MTHFR). a key enzyme in folate metabolism. was recently linked to a significant protection against colon carcinoma and acute lymphoblastic leukaemia in adults. We analysed the genotype frequencies of Ch77T-MTHFR in a group of 143 patients with lymphoproliferative disorders (REAL classification) and 200 controls. Overally, the frequencies of the polymorphic allele were similar (35.3% and 32.0% respectively)(P=0.6). We did not find differences between patients and controls except for myeloma/plasmacytoma group (n=26) which showed a CC genotype less than expected (19% vs 46%) (p=0.01) with a frequency ratio of 0.28 (0.10–0.77). Even among the IgG myeloma cases only one patient showed a common genotype (CC) (1/15. 7%) (P=0.003). If these preliminary data are validated with prospective studies, the 677C allele of MTHFR gene could be confirmed as an effective multiple myeloma protective factor (specially for the IgG casts).

Euclid near-infrared spectrophotometer instrument concept at the end of the phase A study

The Euclid mission objective is to map the geometry of the dark Universe by investigating the distance-redshift relationship and the evolution of cosmic structures. The NISP (Near Infrared Spectro-Photometer) is one of the two Euclid instruments operating in the near-IR spectral region (0.9-2μm). The instrument is composed of: - a cold (140K) optomechanical subsystem constituted by a SiC structure, an optical assembly, a filter wheel mechanism, a grism wheel mechanism, a calibration unit and a thermal control - a detection subsystem based on a mosaic of 16 Teledyne HAWAII2RG 2.4μm. The detection subsystem is mounted on the optomechanical subsystem structure - a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an instrument control unit. This presentation will describe the architecture of the instrument, the expected performance and the technological key challenges. This paper is presented on behalf of the Euclid Consortium.

Three bipods slicer prototype: tests and finite element calculations

For integral field spectroscopy R&D activities in progress at LAM, and particularly in relation with SNAP - SuperNova/Acceleration Probe - spectrograph, LAM has an on-going program to qualify Image Slicers for space instrumentation. In this context, an optomechanical concept of an image slicer supported by three bipods has been designed, realized and tested at the laboratory. This paper presents the mechanical design of the invar mount equipped with three bipods and supporting an assembly of 60 thin zerodur slices tied together thanks to optical contact. We document the design improvement made from last blades flexures prototype and we describe all the tests conducted on this new prototype: optical contact tests, vibration tests and thermal cycles. Thanks to a detailed FEM analysis on this three bipods concept, we correlate simulations with tests.

A spectrograph instrument concept for the Prime Focus Spectrograph (PFS) on Subaru Telescope

We describe the conceptual design of the spectrograph opto-mechanical concept for the SuMIRe Prime Focus Spectrograph (PFS) being developed for the SUBARU telescope. The SuMIRe PFS will consist of four identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each spectrograph will have three channels covering in total, a wavelength range from 380 nm to 1300 nm. The requirements for the instrument are summarized in Section 1. We present the optical design and the optical performance and analysis in Section 2. Section 3 introduces the mechanical design, its requirements and the proposed concepts. Finally, the AIT phases for the Spectrograph System are described in Section 5.

Detectors and cryostat design for the SuMIRe Prime Focus Spectrograph (PFS)

We describe the conceptual design of the camera cryostats, detectors, and detector readout electronics for the SuMIRe Prime Focus Spectrograph (PFS) being developed for the Subaru telescope. The SuMIRe PFS will consist of four identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each spectrograph will have three channels covering wavelength ranges 3800 Å - 6700 Å, 6500 Å - 10000 Å, and 9700 Å - 13000 Å, with the dispersed light being imaged in each channel by a f/1.10 vacuum Schmidt camera. In the blue and red channels a pair of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K x 4K array. For the IR channel, the new Teledyne 4K x 4K, 15 um pixel, mercury-cadmium-telluride sensor with substrate removed for short-wavelength response and a 1.7 um cutoff will be used. Identical detector geometry and a nearly identical optical design allow for a common cryostat design with the only notable difference being the need for a cold radiation shield in the IR camera to mitigate thermal background. This paper describes the details of the cryostat design and cooling scheme, relevant thermal considerations and analysis, and discusses the detectors and detector readout electronics.

The E-NIS instrument on-board the ESA Euclid Dark Energy Mission: a general view after positive conclusion of the assesment phase

The Euclid Near-Infrared Spectrometer (E-NIS) Instrument was conceived as the spectroscopic probe on-board the ESA Dark Energy Mission Euclid. Together with the Euclid Imaging Channel (EIC) in its Visible (VIS) and Near Infrared (NIP) declinations, NIS formed part of the Euclid Mission Concept derived in assessment phase and submitted to the Cosmic Vision Down-selection process from which emerged selected and with extremely high ranking. The Definition phase, started a few months ago, is currently examining a substantial re-arrangement of the payload configuration due to technical and programmatic aspects. This paper presents the general lines of the assessment phase payload concept on which the positive down-selection judgments have been based.

DMD multi-object spectroscopy in space: the EUCLID study

The benefits Astronomy could gain by performing multi-slit spectroscopy in a space mission is renown. Digital Micromirror Devices (DMD), developed for consumer applications, represent a potentially powerful solution. They are currently studied in the context of the EUCLID project. EUCLID is a mission dedicated to the study of Dark Energy developed under the ESA Cosmic Vision programme. EUCLID is designed with 3 instruments on-board: a Visual Imager, an Infrared Imager and an Infrared Multi-Object Spectrograph (ENIS). ENIS is focused on the study of Baryonic Acoustic Oscillations as the main probe, based on low-resolution spectroscopic observations of a very large number of high-z galaxies, covering a large fraction of the whole sky. To cope with these challenging requirements, a highmultiplexing spectrograph, coupled with a relatively small telescope (1.2m diameter) has been designed. Although the current baseline is to perform slit-less spectroscopy, an important option to increase multiplexing rates is to use DMDs as electronic reconfigurable slit masks. A Texas Instrument 2048x1080 Cinema DMD has been selected, and space validation studies started, as a joint ESA-ENIS Consortium effort. Around DMD, a number of suited optical systems has been developed to project sky sources onto the DMD surface and then, to disperse light onto IR arrays. A detailed study started, both at system and subsystem level, to validate the initial proposal. Here, main results are shown, making clear that the use of DMD devices has great potential in Astronomical Instrumentation.

Optical design for the 5-28μm NGST infrared imager MIRI

MIRI is the mid infrared instrument planned for the NGST. Working in the 5-28 μm band, it includes 3 units: a spectrograph, an imager and a calibration facility. We describe here the optical design of the MIRI imager channel as it is at teh end of the phase A study. The MIRI imager provides 3 observing modes: an imaging mode with a field of view of 1.3 arcmin x 1.7 arcmin and a Pixel Field of View of 0.1 arcsec/pixel, a coronagraphic mode and a low resolution spectroscopic mode for point sources, between 5 μm and 10 μm, with a spectral resolution R = λ/Δλ around 100.

DIORAMAS: a wide-field visible and near-infrared imaging multi-slit spectrograph for the EELT

We present the science, design and performances of DIORAMAS, an imager and multi-slit spectrograph for the European Extremely Large Telescope. It covers a wide 6.8x6.8 arcmin2 field, a large wavelength range 0.37 to 1.6 microns. The exceptional performances of this concept will enable extremely deep images to magnitudes AB~30 and high multiplex spectroscopy with up to ~500 slits observed simultaneously at spectral resolutions from R~300 to more than 120 slits at R~3000. The technical design is robust with only proven technology, and DIORAMAS could be developed on a timescale compatible with the EELT first light.