This paper describes the engineering and mechanical considerations in the design and construction of a carbon fiber containment vessel for a photometric camera. The camera is intended for installation on the 4 m William Herschel Telescope, located in Palma, Spain. The scientific objective of the camera system is to measure red-shifts of a large sample of galaxies using the photometric technique. The paper is broken down into sections, divided by the principal engineering challenges of the project; the carbon fiber vacuum vessel, the cooling systems and the precision movement systems.
The PAU (Physics of the Accelerating Universe) project goal is the study of dark energy with a new photometric technique aiming at obtaining photo-z resolution for Luminous Red Galaxies (LRGs) roughly one order of magnitude better than current photometric surveys. To accomplish this, a new large field of view camera (PAUCam) has been built and commissioned at the William Herschel Telescope (WHT). With the current WHT corrector, the camera covers ~1 degree diameter Field of View (FoV). The focal plane consists of 18 2kx4k Hamamatsu fully depleted CCDs, with high quantum efficiency up to 1 μm. To maximize the detector coverage within the FoV, filters are placed in front of the CCD's inside the camera cryostat (made of carbon fiber material) using a challenging movable tray system. The camera uses a set of 40 narrow band filters ranging from ~4400 to ~8600 angstroms complemented with six standard broad-band filters, ugrizY. Here, we describe the camera and its first commissioning results. The PAU project aims to cover roughly 100 square degrees and to obtain accurate photometric redshifts for galaxies down to i<sub>AB</sub> ~ 22:5 detecting also galaxies down to i<sub>AB</sub> ~ 24 with less precision in redshift. With this data set we will obtain competitive constraints in cosmological parameters using both weak lensing and galaxy clustering as main observational probes.
The Dark Energy Camera (DECam) was developed for use by the Dark Energy Survey (DES). The camera will be
installed in the Blanco 4M telescope at the Cerro Tololo Inter-American Observatory (CTIO) and be ready for
observations in the second half of 2012. The focal plane consists of 62 2×4K and 12 2×2K fully depleted CCDs. The
camera provides a 3 sq. degree view and the survey will cover a 5000 sq. degree area. The camera cage and corrector
have already been installed.
The development of the electronics to readout the focal plane was a collaborative effort by multiple institutions in the
United States and in Spain. The goal of the electronics is to provide readout at 250 kpixels/second with less than 15erms
noise. Integration of these efforts and initial testing took place at Fermi National Accelerator Laboratory. DECam
currently resides at CTIO and further testing has occurred in the Coudé room of the Blanco. In this paper, we describe
the development of the readout system, test results and the lessons learned.
The PAU Camera (PAUCam) [1,2] is a wide field camera that will be mounted at the corrected prime focus of the
William Herschel Telescope (Observatorio del Roque de los Muchachos, Canary Islands, Spain) in the next months.
The focal plane of PAUCam is composed by a mosaic of 18 CCD detectors of 2,048 x 4,176 pixels each one with a pixel
size of 15 microns, manufactured by Hamamatsu Photonics K. K. This mosaic covers a field of view (FoV) of 60 arcmin
(minutes of arc), 40 of them are unvignetted.
The behaviour of these 18 devices, plus four spares, and their electronic response should be characterized and optimized
for the use in PAUCam. This job is being carried out in the laboratories of the ICE/IFAE and the CIEMAT.
The electronic optimization of the CCD detectors is being carried out by means of an OG (Output Gate) scan and
maximizing it CTE (Charge Transfer Efficiency) while the read-out noise is minimized.
The device characterization itself is obtained with different tests. The photon transfer curve (PTC) that allows to obtain
the electronic gain, the linearity vs. light stimulus, the full-well capacity and the cosmetic defects. The read-out noise, the
dark current, the stability vs. temperature and the light remanence.
The Dark Energy Survey Collaboration has completed construction of the Dark Energy Camera (DECam), a 3 square
degree, 570 Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be
used to perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the
remainder of the time, and after the survey, DECam will be available as a community instrument. All components of
DECam have been shipped to Chile and post-shipping checkout finished in Jan. 2012. Installation is in progress. A
summary of lessons learned and an update of the performance of DECam and the status of the DECam installation and
commissioning will be presented.
PAUCam consists of an array of 18 red-sensitive CCDs of 4K x 2K pixels with a system of 36 narrow-band (10 nm)
filters and 6 wide-band filters which will be installed at the William Herschel Telescope (WHT). The PAUCam Camera
Control System (CCS) is the software system in charge of the coordination of the several subsystems to acquire
exposures with PAUCam.
The Physics of the Accelerating Universe (PAU) is a project whose main goal is the study of dark energy. For this purpose, a new large field of view camera (the PAU Camera, PAUCam) is being built. PAUCam is designed to carry out a wide area imaging survey with narrow and broad band filters spanning the optical wavelength range. The PAU Camera is now at an advance stage of construction. PAUCam will be mounted at the prime focus of the William Herschel Telescope. With the current WHT corrector, it will cover a 1 degree diameter field of view. PAUCam mounts eighteen 2k×4k Hamamatsu fully depleted CCDs, with high quantum efficiency up to 1 μm. Filter trays are placed in front of the CCDs with a technologically challenging system of moving filter trays inside the cryostat. The PAU Camera will use a new set of 42 narrow band filters ranging from ~4400 to ~8600 angstroms complemented with six standard broad-band filters, ugrizY. With PAUCam at the WHT we will carry out a cosmological imaging survey in both narrow and broad band filters that will perform as a low resolution spectroscopic survey. With the current survey strategy, we will obtain accurate photometric redshifts for galaxies down to <i>i<sub>AB</sub></i>~22.5 detecting also galaxies down to <i>i<sub>AB</sub></i>~24 with less precision in redshift. With this data set we will obtain competitive constraints in cosmological parameters using both weak lensing and galaxy clustering as main observational probes.
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS, a near-infrared multi-object echelle
spectrograph operating at spectral resolution R=20,000 over the 1-2.5μm bandpass) was selected in 2010 by the Gran
Telescopio Canarias (GTC) partnership as the next-generation near-infrared spectrograph for the world's largest
optical/infrared telescope, and is being developed by an international consortium. The MIRADAS consortium includes
the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de
Canarias, Institut de Física d'Altes Energies, Institut d'Estudis Espacials de Catalunya and Universidad Nacional
Autonoma de Mexico, as well as probe arm industrial partner A-V-S (Spain). In this paper, we review the overall system
design for MIRADAS, as it nears Preliminary Design Review in the autumn of 2012.
PAUCam consists of an array of 18 red-sensitive CCDs of 4K x 2K pixels with a system of 36 narrow-band (10 nm)
filters and 6 wide-band filters which will be installed at the William Herschel Telescope (WHT).
PAUCam Slow Control (SC) is the working package of PAUCam in charge of implement all system motion control,
sensors monitoring, actuators control and first security reaction. It is implemented using a Siemens Simotion D435
Motion Controller which controls all the motors and the connected profibus periphery.
The PAUCam  is an optical camera with a 18 CCDs (Hamamatsu Photonics K.K.) mosaic and up to 42 narrow- and
broad-band filters. It is foreseen to install it at the William Herschel Telescope (WHT) in the Observatorio del Roque de
los Muchachos, Canary Islands, Spain. As required by the camera construction, a couple of test bench facilities were
developed, one in Madrid (CIEMAT) that is mainly devoted to CCDs read-out electronics development and filter
characterization , and another in Barcelona (IFAE-ICE) that has as its main task to characterize the scientific CCDs in
terms of Dark Current, CTE, QE, RON and many other parameters demanded by the scientific performance required.
The full CCDs characterization test bench layout, its descriptions and some optical and mechanical characterization
results are summarized in this paper.
The Physics of the Accelerating Universe (PAU) is a new project whose main goal is to study dark energy surveying the
galaxy distribution. For that purpose we need to determine the galaxy redshifts. The most accurate way to determine the
redshift of a galaxy and measure its spectral energy distribution (SED) is achieved with spectrographs. The PAU
collaboration is building an instrument (PAUCam) devoted to perform a large area survey for cosmological studies using
an alternative approach. SEDs are sampled and redshifts determined using narrow band filter photometry. For efficiency
and manufacturability considerations, the filters need to be placed close to the CCD detector surfaces on segmented filter
trays. The most innovative element of PAUCam is a set of 16 different exchangeable trays to support the filters arranged
in a jukebox-like changing mechanism inside the cryostat. The device is designed to operate within the range of
temperatures from 150K to 300K at the absolute pressure of 10<sup>-8</sup>mbar, being class-100 compliant.
The Physics of the Accelerating Universe (PAU) collaboration aims at conducting a competitive cosmology experiment.
For that purpose it is building the PAU Camera (PAUCam) to carry out a wide area survey to study dark energy.
PAUCam has been designed to be mounted at the prime focus of the William Herschel Telescope with its current optical
corrector that delivers a maximum field of view of ~0.8 square degrees. In order to cover the entire field of view
available, the PAUCam focal plane will be populated with a mosaic of eighteen CCD detectors. PAUCam will be
equipped with a set of narrow band filters and a set of broad band filters to sample the spectral energy distribution of
astronomical objects with photometric techniques equivalent to low resolution spectroscopy. In particular it will be able
to determine the redshift of galaxies with good precision and therefore conduct cosmological surveys. PAUCam will also
be offered to the broad astronomical community.
The Dark Energy Survey makes use of a new camera, the Dark Energy Camera (DECam). DECam will be installed in the Blanco 4M telescope at Cerro Tololo Inter-American Observatory (CTIO). DECam is presently under construction
and is expected to be ready for observations in the fall of 2011. The focal plane will make use of 62 2Kx4K and 12
2kx2k fully depleted Charge-Coupled Devices (CCDs) for guiding, alignment and focus. This paper will describe design
considerations of the system; including, the entire signal path used to read out the CCDs, the development of a custom
crate and backplane, the overall grounding scheme and early results of system tests.
The goal of the Dark Energy Survey (DES) is to measure the dark energy equation of state parameter with four
complementary techniques: galaxy cluster counts, weak lensing, angular power spectrum and type Ia supernovae. DES
will survey a 5000 sq. degrees area of the sky in five filter bands using a new 3 deg2 mosaic camera (DECam) mounted
at the prime focus of the Blanco 4-meter telescope at the Cerro-Tololo International Observatory (CTIO). DECam is a
~520 megapixel optical CCD camera that consists of 62 2k x 4k science sensors plus 4 2k x 2k sensors for guiding. The
CCDs, developed at the Lawrence Berkeley National Laboratory (LBNL) and packaged and tested at Fermilab, have
been selected to obtain images efficiently at long wavelengths. A front-end electronics system has been developed
specifically to perform the CCD readout. The system is based in Monsoon, an open source image acquisition system
designed by the National Optical Astronomy Observatory (NOAO). The electronics consists mainly of three types of
modules: Control, Acquisition and Clock boards. The system provides a total of 132 video channels, 396 bias levels and
around 1000 clock channels in order to readout the full mosaic at 250 kpixel/s speed with 10 e- noise performance.
System configuration and data acquisition is done by means of six 0.8 Gbps optical links. The production of the whole
system is currently underway. The contribution will focus on the testing, calibration and general performance of the full
system in a realistic environment.
The Dark Energy Survey Collaboration is building the Dark Energy Camera (DECam), a 3 square degree, 520
Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be used to
perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the
remainder of the time, and after the survey, DECam will be available as a community instrument. Construction of
DECam is well underway. Integration and testing of the major system components has already begun at Fermilab and
the collaborating institutions.