34 research outputs found
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 {\AA} - 6700 {\AA}, 6500 {\AA} - 10000 {\AA},
and 9700 {\AA} - 13000 {\AA}, 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
Prime Focus Spectrograph - Subaru's future -
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 wide-field 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
{\mu}m to 1.3 {\mu}m 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, & JHU in USA, LAM in France, ASIAA in Taiwan, and
NAOJ/Subaru.Comment: 13 pages, 11 figures, submitted to "Ground-based and Airborne
Instrumentation for Astronomy IV, Ian S. McLean, Suzanne K. Ramsay, Hideki
Takami, Editors, Proc. SPIE 8446 (2012)
The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey
We present the design and performance of the multi-object fiber spectrographs
for the Sloan Digital Sky Survey (SDSS) and their upgrade for the Baryon
Oscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999
on the 2.5-m aperture Sloan Telescope at Apache Point Observatory, the
spectrographs produced more than 1.5 million spectra for the SDSS and SDSS-II
surveys, enabling a wide variety of Galactic and extra-galactic science
including the first observation of baryon acoustic oscillations in 2005. The
spectrographs were upgraded in 2009 and are currently in use for BOSS, the
flagship survey of the third-generation SDSS-III project. BOSS will measure
redshifts of 1.35 million massive galaxies to redshift 0.7 and Lyman-alpha
absorption of 160,000 high redshift quasars over 10,000 square degrees of sky,
making percent level measurements of the absolute cosmic distance scale of the
Universe and placing tight constraints on the equation of state of dark energy.
The twin multi-object fiber spectrographs utilize a simple optical layout
with reflective collimators, gratings, all-refractive cameras, and
state-of-the-art CCD detectors to produce hundreds of spectra simultaneously in
two channels over a bandpass covering the near ultraviolet to the near
infrared, with a resolving power R = \lambda/FWHM ~ 2000. Building on proven
heritage, the spectrographs were upgraded for BOSS with volume-phase
holographic gratings and modern CCD detectors, improving the peak throughput by
nearly a factor of two, extending the bandpass to cover 360 < \lambda < 1000
nm, and increasing the number of fibers from 640 to 1000 per exposure. In this
paper we describe the original SDSS spectrograph design and the upgrades
implemented for BOSS, and document the predicted and measured performances.Comment: 43 pages, 42 figures, revised according to referee report and
accepted by AJ. Provides background for the instrument responsible for SDSS
and BOSS spectra. 4th in a series of survey technical papers released in
Summer 2012, including arXiv:1207.7137 (DR9), arXiv:1207.7326 (Spectral
Classification), and arXiv:1208.0022 (BOSS Overview
Prime Focus Spectrograph (PFS) for the Subaru Telescope: Overview, recent progress, and future perspectives
PFS (Prime Focus Spectrograph), a next generation facility instrument on the
8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed,
optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394
reconfigurable fibers will be distributed over the 1.3 deg field of view. The
spectrograph has been designed with 3 arms of blue, red, and near-infrared
cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure
at a resolution of ~1.6-2.7A. An international collaboration is developing this
instrument under the initiative of Kavli IPMU. The project is now going into
the construction phase aiming at undertaking system integration in 2017-2018
and subsequently carrying out engineering operations in 2018-2019. This article
gives an overview of the instrument, current project status and future paths
forward.Comment: 17 pages, 10 figures. Proceeding of SPIE Astronomical Telescopes and
Instrumentation 201
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
The Sloan Digital Sky Survey: Technical Summary
The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed
investigations of the distribution of luminous and non- luminous matter in the
Universe: a photometrically and astrometrically calibrated digital imaging
survey of pi steradians above about Galactic latitude 30 degrees in five broad
optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey
of the approximately one million brightest galaxies and 10^5 brightest quasars
found in the photometric object catalog produced by the imaging survey. This
paper summarizes the observational parameters and data products of the SDSS,
and serves as an introduction to extensive technical on-line documentation.Comment: 9 pages, 7 figures, AAS Latex. To appear in AJ, Sept 200
Progress with the Prime Focus Spectrograph for the Subaru Telescope: a massively multiplexed optical and near-infrared fiber spectrograph
The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber
spectrograph with 2394 science fibers, which are distributed in 1.3 degree
diameter field of view at Subaru 8.2-meter telescope. The simultaneous wide
wavelength coverage from 0.38 um to 1.26 um, with the resolving power of 3000,
strengthens its ability to target three main survey programs: cosmology,
Galactic archaeology, and galaxy/AGN evolution. A medium resolution mode with
resolving power of 5000 for 0.71 um to 0.89 um also will be available by simply
exchanging dispersers. PFS takes the role for the spectroscopic part of the
Subaru Measurement of Images and Redshifts project, while Hyper Suprime-Cam
works on the imaging part. To transform the telescope plus WFC focal ratio, a
3-mm thick broad-band coated glass-molded microlens is glued to each fiber tip.
A higher transmission fiber is selected for the longest part of cable system,
while one with a better FRD performance is selected for the fiber-positioner
and fiber-slit components, given the more frequent fiber movements and tightly
curved structure. Each Fiber positioner consists of two stages of
piezo-electric rotary motors. Its engineering model has been produced and
tested. Fiber positioning will be performed iteratively by taking an image of
artificially back-illuminated fibers with the Metrology camera located in the
Cassegrain container. The camera is carefully designed so that fiber position
measurements are unaffected by small amounts of high special-frequency
inaccuracies in WFC lens surface shapes. Target light carried through the fiber
system reaches one of four identical fast-Schmidt spectrograph modules, each
with three arms. Prototype VPH gratings have been optically tested. CCD
production is complete, with standard fully-depleted CCDs for red arms and
more-challenging thinner fully-depleted CCDs with blue-optimized coating for
blue arms.Comment: 14 pages, 12 figures, submitted to "Ground-based and Airborne
Instrumentation for Astronomy V, Suzanne K. Ramsay, Ian S. McLean, Hideki
Takami, Editors, Proc. SPIE 9147 (2014)