The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 square degrees will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We present an overview of the instrumentation, the main technical requirements and challenges, and the current status of the project.
PAUCam is a large field of view camera designed to exploit the field delivered by the prime focus corrector of the William Herschel Telescope, at the Observatorio del Roque de los Muchachos. One of the new features of this camera is its filter system, placed within a few millimeters of the focal plane using eleven trays containing 40 narrow band and 6 broad band filters, working in vacuum at an operational temperature of 250K and in a focalized beam. In this contribution, we describe the performance of these filters both in the characterization tests at the laboratory.
The PAUCam is an optical camera with a wide field of view of 1 deg x 1 deg and up to 46 narrow and broad band filters. The camera is already installed on the William Herschel Telescope (WHT) in the Canary Islands, Spain and successfully commissioned during the first period of 2015. The paper presents the main results from the readout electronics commissioning tests and include an overview of the whole readout electronics system, its configuration and current performance.
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 PAUCam is an optical camera with an array of 18 CCDs (Hamamatsu Photonics K.K.) and up to 45 narrow and
broad band filters. The camera will be installed on the William Herschel Telescope (WHT) in the Canary Islands, Spain.
In order to fulfill with the specifications for the camera readout system, it was necessary to test the different readout
electronics subsystems individually before to integrate the final readout work package, which is composed of 4
MONSOON (NOAO) front-ends, 6 fan out boards (MIX), each one driving up to 5 CCDs signals and a pre-amplification
stage (PREAMP) located inside the cryostat. To get the subsystems integration, it was built a small camera prototype
using the same technology as used in the main camera: a carbon fiber cryostat refrigerated by a cryotiger cooling system
but with capacity to allocate just 2 CCDs, which were readout and re-characterized to measure the electronics
performance as conversion factor or gain, readout noise, stability, linearity, etc. while the cross-talk was measured by
using a spot-light.
The aim of this paper is to review the whole process of assembly, integration and test (AIT) of the readout electronics
work package and present the main results to demonstrate the viability of the proposed systems to be use with the
The focal plane of the PAU camera is composed of eighteen 2K x 4K CCDs. These devices, plus four spares, were
provided by the Japanese company Hamamatsu Photonics K.K. with type no. S10892–04(X). These detectors are 200
μm thick fully depleted and back illuminated with an n-type silicon base. They have been built with a specific coating to
be sensitive in the range from 300 to 1,100 nm. Their square pixel size is 15 μm.
The read-out system consists of a Monsoon controller (NOAO) and the panVIEW software package. The deafualt CCD
read-out speed is 133 kpixel/s. This is the value used in the calibration process.
Before installing these devices in the camera focal plane, they were characterized using the facilities of the ICE (CSIC–
IEEC) and IFAE in the UAB Campus in Bellaterra (Barcelona, Catalonia, Spain).
The basic tests performed for all CCDs were to obtain the photon transfer curve (PTC), the charge transfer efficiency
(CTE) using X-rays and the EPER method, linearity, read-out noise, dark current, persistence, cosmetics and quantum
The X-rays images were also used for the analysis of the charge diffusion for different substrate voltages (VSUB).
Regarding the cosmetics, and in addition to white and dark pixels, some patterns were also found. The first one, which
appears in all devices, is the presence of half circles in the external edges. The origin of this pattern can be related to the
assembly process. A second one appears in the dark images, and shows bright arcs connecting corners along the vertical
axis of the CCD. This feature appears in all CCDs exactly in the same position so our guess is that the pattern is due to
Finally, and just in two devices, there is a spot with wavelength dependence whose origin could be the result of a
defectous coating process.
The Physics of Accelerating Universe Camera (PAUCam) is a new camera for dark energy studies that will be installed
in the William Herschel telescope. The main characteristic of the camera is the capacity for high precision photometric
redshift measurement. The camera is composed of eighteen Hamamatsu Photonics CCDs providing a wide field of view
covering a diameter of one degree. Unlike the common five optical filters of other similar surveys, PAUCam has forty
optical narrow band filters which will provide higher resolution in photometric redshifts. In this paper a general
description of the electronics of the camera and its status is presented.
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.
PAUCam is a new camera for studying the physics of the accelerating universe. The camera will consist of eighteen
2Kx4K HPK CCDs: sixteen for science and two for guiding. The camera will be installed at the prime focus of the WHT
(William Herschel Telescope). In this contribution, the architecture of the readout electronics system is presented. Back-
End and Front-End electronics are described. Back-End consists of clock, bias and video processing boards, mounted on
Monsoon crates. The Front-End is based on patch panel boards. These boards are plugged outside the camera feed-through
panel for signal distribution. Inside the camera, individual preamplifier boards plus kapton cable completes the
path to connect to each CCD. The overall signal distribution and grounding scheme is shown in this paper.
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.
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.
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 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 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 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 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 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.
The Dark Energy Camera will be comprised of 74 CCDs with high efficiency out to a wavelength of 1 micron.
The CCDs will be read out by a Monsoon-based system consisting of three boards: Master Control, CCD
Acquisition, and Clock boards. The charge transfer efficiency (CTE) is closely related to the clock waveforms
provided by the Clock Board (CB). The CB has been redesigned to meet the stringent requirements of the Dark
Energy Survey. The number of signals provided by the clock board has been extended from 32 (the number
required for 2 CCDs) up to 135 signals (the number required for 9 CCDs). This modification is required to fit
the electronics into the limited space available on the imager vessel. In addition, the drivers have been changed
to provide more current. The first test result with the new clock board shows a clear improvement in the CTE
response when reading out at the higher frequencies required for the guide CCDs.
The Dark Energy Survey Camera (DECam), when completed, is going to have one of the largest existing focal planes,
equipped with more than 70 CCDs. Due to the large number of CCDs and the tight space on the camera, the DECam
electronics group has developed new compact front-end electronics capable of flexibly and rapidly reading out all the
focal plane CCDs. The system is based on the existing MONSOON Image Acquisition System designed by the National
Optical Astronomy Observatory (NOAO), and it is currently being used for testing and characterization of CCDs. Boards
for the new readout are being developed in USA and Spain, with the first prototypes already produced and tested. The
next version with some improvements will be tested during 2008 and the system will be ready for production at the
beginning of 2009. Custom MONSOON boards and the electronics path will be described.
We describe the Dark Energy Camera (DECam), which will be the primary instrument used in the Dark Energy Survey.
DECam will be a 3 sq. deg. mosaic camera mounted at the prime focus of the Blanco 4m telescope at the Cerro-Tololo
International Observatory (CTIO). DECam includes a large mosaic CCD focal plane, a five element optical corrector,
five filters (g,r,i,z,Y), and the associated infrastructure for operation in the prime focus cage. The focal plane consists of
62 2K x 4K CCD modules (0.27"/pixel) arranged in a hexagon inscribed within the roughly 2.2 degree diameter field of
view. The CCDs will be 250 micron thick fully-depleted CCDs that have been developed at the Lawrence Berkeley
National Laboratory (LBNL). Production of the CCDs and fabrication of the optics, mechanical structure, mechanisms,
and control system for DECam are underway; delivery of the instrument to CTIO is scheduled for 2010.
A description of the plans and infrastructure developed for CCD testing and characterization for the DES focal plane detectors is presented. Examples of the results obtained are shown and discussed in the context of the device requirements for the survey instrument.