Modern Skipper CCD technology has been used in particle physics experiments since its first successful demonstration in 2017. This technology has been demonstrated to achieve extremely low readout noise (0.039 e-rms/pix), while maintaining the benefits of conventional CCD detectors. The extremely low noise of Skipper CCDs presents a very interesting potential for certain astronomical applications where photon shot noise does not dominate, and the ability of Skipper CCDs to be tuned for a desired readout noise allows for a wide range of applications. In the current paper, we focus on the engineering work performed in cryo-mechanics and electronics (Dewar, detector mount, preamplifier, etc.) at NOIRLab-CTIO in order to perform on-sky testing of a mosaic of 4 Skipper CCDs using the SOAR Integral Field Spectrograph (SIFS). This work was performed in the context of a NOIRLab/LNA/Fermilab/U.Chicago/LBNL collaboration for testing Skipper devices for astronomy. We also present the mosaic characterization results of the detectors from the laboratory, as well as the final engineering performance results from on sky observations.
We present the development of a Skipper Charge-Coupled Device (CCD) focal plane prototype for the SOAR Telescope Integral Field Spectrograph (SIFS). This mosaic focal plane consists of four 6k × 1k, 15 μm pixel Skipper CCDs mounted inside a vacuum dewar. We describe the process of packaging the CCDs so that they can be easily tested, transported, and installed in a mosaic focal plane. We characterize the performance of ∼ 650μm thick, fully-depleted engineering-grade Skipper CCDs in preparation for performing similar characterization tests on science-grade Skipper CCDs which will be thinned to 250μm and backside processed with an antireflective coating. We achieve a single-sample readout noise of 4.5 e− rms/pix for the best performing amplifiers and subelectron resolution (photon counting capabilities) with readout noise σ ∼ 0.16 e− rms/pix from 800 measurements of the charge in each pixel. We describe the design and construction of the Skipper CCD focal plane and provide details about the synchronized readout electronics system that will be implemented to simultaneously read 16 amplifiers from the four Skipper CCDs (4-amplifiers per detector). Finally, we outline future plans for laboratory testing, installation, commissioning, and science verification of our Skipper CCD focal plane.
CUBES is a high-efficiency, medium-resolution (R ≃ 20, 000) spectrograph dedicated to the “ground based UV”
(approximately the wavelength range from 300 to 400nm) destined for the Cassegrain focus of one of ESO’s VLT
unit telescopes in 2018/19. The CUBES project is a joint venture between ESO and Instituto de Astronomia,
Geof´ısica e Ciˆencias Atmosf´ericas (IAG) at the Universidade de S˜ao Paulo and the Brazilian Laborat´orio Nacional
de Astrofs´ıca (LNA). CUBES will provide access to a wealth of new and relevant information for stellar as well as
extra-galactic sources. Principle science cases include the study of heavy elements in metal-poor stars, the direct
determination of carbon, nitrogen and oxygen abundances by study of molecular bands in the UV range and the
determination of the Beryllium abundance as well as the study of active galactic nuclei and the inter-galactic
medium. With a streamlined modern instrument design, high efficiency dispersing elements and UV-sensitive
detectors, it will enable a significant gain in sensitivity over existing ground based medium-high resolution
spectrographs enabling vastly increased sample sizes accessible to the astronomical community. We present here
a brief overview of the project, introducing the science cases that drive the design and discussing the design
options and technological challenges.
The Fiber Optical Cable and Connector System (FOCCoS), provides optical connection between 2400
positioners and a set of spectrographs by an optical fibers cable as part of Subaru PFS instrument. Each positioner
retains one fiber entrance attached at a microlens, which is responsible for the F-ratio transformation into a larger one so
that difficulties of spectrograph design are eased. The optical fibers cable will be segmented in 3 parts at long of the
way, cable A, cable B and cable C, connected by a set of multi-fibers connectors. Cable B will be permanently attached
at the Subaru telescope. The first set of multi-fibers connectors will connect the cable A to the cable C from the
spectrograph system at the Nasmith platform. The cable A, is an extension of a pseudo-slit device obtained with the
linear disposition of the extremities of the optical fibers and fixed by epoxy at a base of composite substrate. The second
set of multi-fibers connectors will connect the other extremity of cable A to the cable B, which is part of the positioner's
device structure. The optical fiber under study for this project is the Polymicro FBP120170190, which has shown very
encouraging results. The kind of test involves FRD measurements caused by stress induced by rotation and twist of the
fiber extremity, similar conditions to those produced by positioners of the PFS instrument. The multi-fibers connector
under study is produced by USCONEC Company and may connect 32 optical fibers. The tests involve throughput of
light and stability after many connections and disconnections. This paper will review the general design of the FOCCoS
subsystem, methods used to fabricate the devices involved and the tests results necessary to evaluate the total efficiency
of the set.
The SOAR Telescope Echelle Spectrograph - STELES - is part of the Brazilian participation on the 4.1m SOAR
telescope second-generation instrumentation. In view of SOAR´s high image quality and moderately large collecting
area and the near UV capability, it will be able to yield high quality spectroscopic data for a large variety of objects of
astrophysical interests. The spectrograph is a R4 cross-dispersed echelle fed by the SOAR Nasmyth focus, operating in a
quasi-Littrow white pupil configuration, and a resolving power of R ≈ 50,000, covering the 300-900nm spectral range in
one shot.
STELES is a bench spectrograph which will be mounted vertically on one side of the SOAR Telescope fork. The ninetydegree
inversion of the mechanical components, due to the vertical position of the instrument, plus the close proximity of
most components, due to the spectrograph compactness, were requirements carefully observed during the mechanical
design process. This paper describes the mechanical characteristics of the individual assemblies that make up the
STELES mechanical design. The STELES instrument can be separated into two sections, the fore optics, and the
spectrograph. The fore optics has the mechanisms from the SOAR telescope down to the STELES bench spectrograph,
and the bench spectrograph has the mechanisms for the spectrograph covering the red and blue spectrum.
ECHARPE spectrograph - Espectrógrafo ECHelle de Alta Resolução para o telescópio Perkin-Elmer - is being
designed at LNA - Laboratório Nacional de Astrofísica, Brazil - to be mounted on 1.60 meter telescope at Pico dos
Dias Observatory, Brazil. It will offer a spectral resolution of R ~ 50000, in the interval 390-900 nm and in a single
exposition. It will be a fiber fed, bench spectrograph with two channels: blue and red, fed by two optical fibers (object,
sky or calibration) with aperture of 1.5 or 2.0 arcseconds. This paper reports on technical characteristics of the
spectrograph mechanical design and presents a new developed mounting system for echelle grating and collimator and
relay mirrors, which allows linear and rotational adjustments in all degrees of freedom without using springs.
At least during the last ten years, the Brazilian astronomical community has been asking for an echelle spectrograph for
the 1.6 m telescope installed at Pico dos Dias Observatory (Brazópolis, MG, Brazil, OPD/MCTI/LNA). Among the
scientific cases are topics related to the chemical evolution of the Galaxy, asteroseismology, chemical composition and
chromospheric activities of solar type stars and the relations between solar analogues and terrestrial planets. During 2009
the project finally got started. The called ECHARPE spectrograph (Espectrógrafo ECHelle de Alta Resolução para o
telescópio Perkin-Elmer) is being projected to offer a spectral resolution of R ~ 50000, in the range 390-900 nm and with
a single exposition. It will be a bench spectrograph with two channels: blue and red, fed by two optical fibers (object, sky
or calibration) with aperture of 1.5 or 2.0 arcseconds. The instrument will be placed in one of the telescope pillar
ramification, in the originals installations of a Coudé spectrograph and in a specially created environment controlled
room. In this work we will present the scientific motivations, the conceptual optical design, the expected performance of
the spectrograph, and the status of its development. ECHARPE is expected to be delivered to the astronomical
community in 2014, fully prepared and optimized for remote operations.
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.
The SOAR Integral Field Unit Spectrograph (SIFS) is fed by an integral field unit composed of a bi-dimensional
arrangement of 1300 optical fibers. It has been developed in Brazil by a team of scientists and engineers led by the
National Laboratory of Astrophysics (MCT/LNA) and the Department of Astronomy of the Institute of Astronomy,
Geophysics and Atmospheric Sciences of the University of São Paulo (IAG/USP). It comprises three major subsystems;
a fore-optics installed on the Nasmyth port of the telescope or the SOAR Adaptive Optics Module, a 14-m optical fiber
IFU, and a bench-mounted spectrograph installed on the telescope fork. SIFS is successfully assembled and tested on the
SOAR Telescope in Chile and has now moved to the commissioning phase. This paper reports on technical
characteristics of the mechanical design and the assembly, integration and technical activities.
SIFS is a lenslet/fiber Integral Field Unit Spectrograph which has just been delivered to the SOAR 4.1m telescope in
Chile. The instrument was designed and constructed by the National Laboratory of Astrophysics (MCT/LNA) in
collaboration with the Department of Astronomy of the Institute of Astronomy, Geophysics and Atmospheric Sciences of
the University of Sao Paulo (IAG/USP). It is designed to operate at both the raw Nasmyth and the SAM (the SOAR
Adaptive Optics Module) which delivers GLAO-corrected images in optical wave-bands longward of 500nm. The
lenslets have a 1mm pitch feeding a set of 1,300 fibres in a 26-by-50 format. Sets of deployable fore-optics convert the
f/16.5 input beam to give samplings between ~0.1 and 0.3 arcsec. The fiber output is in the form of a curved, pupil-centric,
long-slit which is fed into a bench-mounted spectrograph. An off-axis Maksutov collimates the beam onto a set
of VPH gratings and thence imaged by an f/3 refractive camera onto a 2-by-1 mosaic of 2k-by-4k E2V CCDs. The
camera is articulated over a >90 deg. angle to allow the grating/camera combination to operate in a transmission Littrow
configuration. The wavelength range is limited by the CCDs to the 350 to 1000nm range with spectral resolution
maxima of ~20,000. The paper will review the optical design of the spectrograph and the methods used to fabricate the
lenslet/fiber IFU.
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