Eric Prieto

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.

VIMOS and NIRMOS multi-object spectrographs for the ESO VLT

The VIRMOS consortium of French and Italian Institutes is manufacturing 2 wide field imaging multi-object spectrographs for the European Southern Observatory Very Large Telescope, with emphasis on the ability to carry over spectroscopic surveys of large numbers of sources. The Visible Multi-Object Spectrograph, VIMOS, is covering the 0.37 to 1 micron wavelength domain, with a full field of view of 4 by 7 by 8 arcmin2 in imaging and MOS mode. The Near IR Multi-Object Spectrograph, NIRMOS, is covering the 0.9 to 1.8 microns wavelength range, with afield of view 4 by 6 by 8 arcmin2 in MOS mode. The spectral resolution for both instrument scan reach up to R equals 5000 for a 0.5 arcsec wide slit. Multi-slit masks are produced by a dedicated Mask Manufacturing Machine cutting through thin Invar sheets and capable of producing 4 slit masks approximately 300 by 300 mm each with approximately slits 5.7 mm long in less than one hour. Integral field spectroscopy is made possible in VIMOS by switching in the beam specially build masks fed by 6400 fibers coming form a 54 by 54 arcsec2 integral field head with a 80 by 80 array of silica micro-lenses. NIRMOS has a similar IFS unit with a field of 30 by 30 arcmin2. These instruments are designed to offer very large multiplexing capabilities. In MOS mode, about 1000 objects can be observed simultaneously with VIMOS, with a S/N equals 10 obtained on galaxies with I equals 24 in one hour, and approximately 200 objects can be observed simultaneously with NIRMOS, with a S/N equals 10 obtained don galaxies with J equals 22, H equals 20.6 in 1h at Req equals 200. We present here the status of VIMOS, currently under final integration, with expected first light in the summer 2000, together with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more than 150000 galaxies over the redshift range 0 < z < 5 will be undertaken based on 120 guaranteed nights awarded to the project.

NIRSpec: near-infrared spectrograph for the JWST

The James Webb Space Telescope (JWST) is a passively cooled, 6.5m aperture class telescope, optimized for diffraction-limited performance in the near-infrared wavelength region (1 - 5 μm). JWST will be capable of high-resolution imaging and spectroscopy and will carry a scientific payload consisting of three scientific instruments. One of the instruments - NIRSpec - is a near-infrared, multi-object, dispersive spectrograph, which will be provided by ESA. EADS Astrium and its subcontractors have been involved in all ESA instrument studies for JWST. The actual NIRSpec design has evolved during three years of studying of different spectrometer design and performance options. Basic feature of the current design is the all ceramic material concept for the instrument structure and mirror optics; both were successfully tested on component level. This paper presents our NIRSpec design concept and its predicted performance.

SNAP focal plane

The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square-degree field sensitive in the visible and near-infrared wavelength regime. We describe the requirements for the instrument suite and the evolution of the focal plane design to the present concept in which all the instrumentation -- visible and near-infrared imagers, spectrograph, and star guiders -- share one common focal plane.The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square-degree field sensitive in the visible and near-infrared wavelength regime. We describe the requirements for the instrument suite and the evolution of the focal plane design to the present concept in which all the instrumentation -- visible and near-infrared imagers, spectrograph, and star guiders -- share one common focal plane.

Design, prototypes, and performances of an image slicer system for integral field spectroscopy

A research and development activity on an Image Slicer System for Integral Field Spectroscopy is conducted with possible applications on future instrumentation for major ground-based (VLT second-generation instruments) and space (NGST, SNAP) observatories. These instruments need high-photometric accuracy, compactness and will possibly work under cryogenic environment, while multi-integral field units may require mass production. Several prototypes have been manufactured since March 2000. This paper provides an overview of the difficulties and limits of the design for different applications, and will describe technology developments and performance evaluation. In particular, the assembly of Zerodur micro-optical elements required an original method of assembly using high precision molecular adhesion, in order to comply with optical tolerances. Following the exact characteristics of the optical elements, diffraction and straylight analyses have been performed in the NIR range. It was found that diffraction effects due to the image slicer induce energy losses less than a few percents and do not induce any crosstalk between pseudo-slits. With a good baffling, scatter can be controlled to minimize the background increase to less than 10-4 times the incident flux.

Very wide Integral Field unit of virmos for the VLT : Design and performances

This paper presents the VLT-VIMOS Integral Field Spectroscopy Unit. This unit allows to observe a very large 54 inch by 54 inch field on one edge of the VIMOS instrument multi-object field. This unit contains 6400 sets of (mu) lenses-fibers-(mu) lenses, producing the equivalent of a 72 arcminute by 0.67 arcsec slit projected on the sky. Two spatial resolution are offered, coupled with the low and high spectral resolution of VIMOS. The design philosophy, technological choices and the first test result of the assembled unit are presented.

ESA NGST integral field and multiobject spectrograph slicer system

An Integral Field and Multiobject Spectrograph (IFMOS) for NGST has been studied for the European Space Agency by a European consortium. This paper describes the design of the integral field unit (IFU), the optical system which divides up the 2D field and reformats in into one or more slits. The IFU uses the Advanced Image Slicer concept, which has many advantages over other designs of IFU and is particularly well suited to space applications.

VIRMOS: visible and infrared multiobject spectrographs for the VLT

We present the current design of the VIsible Multi-Object Spectrograph (VIMOS) and the Near InfraRed Multi-Object Spectrograph (NIRMOS) for the European Southern Observatory Very Large Telescope. The basic scientific requirement is to conduct very deep redshift surveys of large quantities of objects, in a minimum number of nights. The technical specifications are to allow for a large multiplex gain over a wide field, and a high efficiency of the optical train, over the 0.37 to 1.8 micrometer domain. The baseline technical concept is built around 4 channels, covering 4 X 7 X 8 arcmin2 for VIMOS and 4 X 7 X 7 arcmin2 for NIRMOS. Each channel is an imaging spectrograph with a large field adaptation lens, a collimator, grisms or filters, and a F/1.8 camera, coupled to a 2048 X 4096 pixels CCD for VIMOS, and a 20482 HgCdTe Rockwell array for NIRMOS. The unique multiplex gain allows to obtain spectra of up to 840 object simultaneously with VIMOS, and up to 170 with NIRMOS (10 arcsec slits). An integral field spectroscopy mode with more than 6400 fibers coupled to micro-lenses will be available for VIMOS, covering a 1 X 1 arcmin2 field. The VLT-VIRMOS survey of more than 150,000 galaxies is planned down to magnitudes IAB equals 24, coupled to an ultra deep probe to IAB equals 26.

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.

Original image slicer designed for integral field spectroscopy with the near-infrared spectrograph for the James Webb Space Telescope

Integral field spectroscopy (IFS) provides a spectrum simultaneously for each spatial sample of an extended 2-D field. It consists of an integral field unit (IFU), which slices and rearranges the initial field along the entrance slit of a spectrograph. We present an original design of IFU based on the advanced image slicer concept. To reduce optical aberrations, pupil and slit mirrors are disposed in a fan-shaped configuration, which means that angles between incident and reflected beams on each element are minimized. The fan-shaped image slicer improves image quality in terms of wavefront error by a factor of 2 compared with a classical image slicer, and furthermore, it guaranties a negligible level of differential aberration in the field. As an example, we present the design LAM used for its proposal at the near-infrared spectrograph (NIRSpec/IFU) invitation of tender for the James Webb Space Telescope (JWST).