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Full list of authors: Silber, Joseph Harry; Fagrelius, Parker; Fanning, Kevin; Schubnell, Michael; Aguilar, Jessica Nicole; Ahlen, Steven; Ameel, Jon; Ballester, Otger; Baltay, Charles; Bebek, Chris; Beard, Dominic Benton; Besuner, Robert; Cardiel-Sas, Laia; Casas, Ricard; Castander, Francisco Javier; Claybaugh, Todd; Dobson, Carl; Duan, Yutong; Dunlop, Patrick; Edelstein, Jerry; Emmet, William T.; Elliott, Ann; Evatt, Matthew; Gershkovich, Irena; Guy, Julien; Harris, Stu; Heetderks, Henry; Heetderks, Ian; Honscheid, Klaus; Maria Illa, Jose; Jelinsky, Patrick; Jelinsky, Sharon R.; Jimenez, Jorge; Karcher, Armin; Kent, Stephen; Kirkby, David; Kneib, Jean-Paul; Lambert, Andrew; Lampton, Mike; Leitner, Daniela; Levi, Michael; McCauley, Jeremy; Meisner, Aaron; Miller, Timothy N.; Miquel, Ramon; Mundet, Julia; Poppett, Claire; Rabinowitz, David; Reil, Kevin; Roman, David; Schlegel, David; Serrano, Santiago; Van Shourt, William; Sprayberry, David; Tarle, Gregory; Tie, Suk Sien; Weaverdyck, Curtis; Zhang, Kai; Azzaro, Marco; Bailey, Stephen; Becerril, Santiago; Blackwell, Tami; Bouri, Mohamed; Brooks, David; Buckley-Geer, Elizabeth; Penate Castro, Jose; Derwent, Mark; Dey, Arjun; Dhungana, Govinda; Doel, Peter; Eisenstein, Daniel J.; Fahim, Nasib; Garcia-Bellido, Juan; Gaztanaga, Enrique; Gontcho, Satya Gontcho A.; Gutierrez, Gaston; Horler, Philipp; Kehoe, Robert; Kisner, Theodore; Kremin, Anthony; Kronig, Luzius; Landriau, Martin; Le Guillou, Laurent; Martini, Paul; Moustakas, John; Palanque-Delabrouille, Nathalie; Peng, Xiyan; Percival, Will; Prada, Francisco; Allende Prieto, Carlos; Gonzalez de Rivera, Guillermo; Sanchez, Eusebio; Sanchez, Justo; Sharples, Ray; Soares-Santos, Marcelle; Schlafly, Edward; Weaver, Benjamin Alan; Zhou, Zhimin; Zhu, Yaling; Zou, Hu; DESI Collaboration.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., A system of 5020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically retarget their optical fibers every 10–20 minutes, each to a precision of several microns, with a reconfiguration time of fewer than 2 minutes. Over the next 5 yr, they will enable the newly constructed Dark Energy Spectroscopic Instrument (DESI) to measure the spectra of 35 million galaxies and quasars. DESI will produce the largest 3D map of the universe to date and measure the expansion history of the cosmos. In addition to the 5020 robotic positioners and optical fibers, DESI's Focal Plane System includes six guide cameras, four wave front cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. The system also includes associated structural, thermal, and electrical systems. In all, it contains over 675,000 individual parts. We discuss the design, construction, quality control, and integration of all these components. We include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multiobject, fiber-fed spectrographs. © 2022. The Author(s). Published by the American Astronomical Society., The authors in the Barcelona-Madrid Regional Participation Group (BCN-MAD RPG) wish to acknowledge support by MICIN under grants PID2019-111317 GB, PGC2018-094773, PGC2018-102021, SEV-2016-0588, SEV-2016-0597, MDM-2015-0509, and CEX2020-001058-M, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. M.A., S.B., N.F., F.P., G.G.R., and J.S. acknowledge support from the Spanish MICINN grants MultiDark CSD2009-00064, IFT-UAM/CSIC Severo Ochoa Award SEV-2012-0249 and AYA2014-60641-C2-1-P, CSIC-AVS contract through MICINN grant AYA2010-21231-C02-01 and CDTI grant IDC-20101033, and support from the Campus of International Excellence UAM+CSIC. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under Contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institutions., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

The PAU (Physics of the Accelerating Universe) Survey goal is to obtain photometric redshifts (photo-z) and Spectral Energy Distribution (SED) of astronomical objects with a resolution roughly one order of magnitude better than current broad band photometric surveys. To accomplish this, a new large field of view camera (PAUCam) has been designed, built, commissioned and is now operated at the William Herschel Telescope (WHT). With the current WHT Prime Focus corrector, the camera covers ~1-degree diameter Field of View (FoV), of which, only the inner ~40 arcmin diameter are unvignetted. The focal plane consists of a mosaic of 18 2k$x4k Hamamatsu fully depleted CCDs, with high quantum efficiency up to 1 micrometers in wavelength. To maximize the detector coverage within the FoV, filters are placed in front of the CCDs inside the camera cryostat (made out of carbon fiber) using a challenging movable tray system. The camera uses a set of 40 narrow band filters ranging from ~4500 to ~8500 Angstroms complemented with six standard broad-band filters, ugrizY. The PAU Survey aims to cover roughly 100 square degrees over fields with existing deep photometry and galaxy shapes to obtain accurate photometric redshifts for galaxies down to i_AB~22.5, detecting also galaxies down to i_AB~24 with less precision in redshift. With this data set we will be able to measure intrinsic alignments, galaxy clustering and perform galaxy evolution studies in a new range of densities and redshifts. Here, we describe the PAU camera, its first commissioning results and performance., 34 pages, 55 figures

We describe the first public data release of the Dark Energy Survey, DES DR1, consisting of reduced single epoch images, coadded images, coadded source catalogs, and associated products and services assembled over the first three years of DES science operations. DES DR1 is based on optical/near-infrared imaging from 345 distinct nights (August 2013 to February 2016) by the Dark Energy Camera mounted on the 4-m Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. We release data from the DES wide-area survey covering ~5,000 sq. deg. of the southern Galactic cap in five broad photometric bands, grizY. DES DR1 has a median delivered point-spread function of g = 1.12, r = 0.96, i = 0.88, z = 0.84, and Y = 0.90 arcsec FWHM, a photometric precision of < 1% in all bands, and an astrometric precision of 151 mas. The median coadded catalog depth for a 1.95" diameter aperture at S/N = 10 is g = 24.33, r = 24.08, i = 23.44, z = 22.69, and Y = 21.44 mag. DES DR1 includes nearly 400M distinct astronomical objects detected in ~10,000 coadd tiles of size 0.534 sq. deg. produced from ~39,000 individual exposures. Benchmark galaxy and stellar samples contain ~310M and ~ 80M objects, respectively, following a basic object quality selection. These data are accessible through a range of interfaces, including query web clients, image cutout servers, jupyter notebooks, and an interactive coadd image visualization tool. DES DR1 constitutes the largest photometric data set to date at the achieved depth and photometric precision., 30 pages, 20 Figures. Release page found at this url https://des.ncsa.illinois.edu/releases/dr1

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. © 2018 SPIE., This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under Contract No. DEAC0205CH1123, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under Contract No. AST-0950945 to the National Optical Astronomy Observatory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the National Council of Science and Technology of Mexico, and by the DESI Member Institutions. The authors are honored to be permitted to conduct astronomical research on Iolkam Du'ag (Kitt Peak), a mountain with particular significance to the Tohono O'odham Nation.

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.

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.

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 iAB ~ 22:5 detecting also galaxies down to iAB ~ 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 is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. The camera consists of a five element optical corrector, seven filters, a shutter with a 60 cm aperture, and a CCD focal plane of 250 micron thick fully-depleted CCDs cooled inside a vacuum Dewar. The 570 Mpixel focal plane comprises 62 2kx4k CCDs for imaging and 12 2kx2k CCDs for guiding and focus. The CCDs have 15 microns x15 microns pixels with a plate scale of 0.263 arc sec per pixel. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 seconds with 6-9 electrons readout noise. This paper provides a technical description of the camera's engineering, construction, installation, and current status., Comment: submitted to AJ Corresponding Authors H. T. Diehl (diehl@fnal.gov)

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 efficiency. 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 electrical fields. 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 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 PAUCam camera.

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 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 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 Coude room of the Blanco. In this paper, we describe the development of the readout system, test results and the lessons learned.

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 AB ~22.5 detecting also galaxies down to i AB ~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 [1] 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 [2], 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 Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS, a near-infrared multi-object echelle spectrograph operating at spectral resolution R=20,000 over the 1-2.5 mu m 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 Astrofisica de Canarias, Institut de Fisica 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 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 -8 mbar, being class-100 compliant.

In response to an Announcement of Opportunity for new instrumentation for the Gran Telescopio Canarias (GTC) issued on October 2009, an international team led by the University of Florida and composed of scientists and engineers from 8 institutions in 3 countries submitted a proposal for building a highly powerful instrument within the required envelope and budget. The MIRADAS instrument will be a common user NIR multi object spectrograph equipped with a sophisticated multiplexing system (MXS) able to deliver spectral resolutions of R~20,000 in the wavelength range from 1 to 2.5 microns for up to 20 objects simultaneously sparsely distributed over a field of regard of 5 arcmin in diameter. In this paper, we summarize the main instrumental features of the proposed instrument which is under review by the GTC Project Office.

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.

Benítez, Narciso et al., arXiv:0807.0535v2, Baryon Acoustic Oscillations (BAOs) provide a "standard ruler" of known physical length, making it one of the most promising probes of the nature of dark energy (DE). The detection of BAOs as an excess of power in the galaxy distribution at a certain scale requires measuring galaxy positions and redshifts. "Transversal" (or "angular") BAOs measure the angular size of this scale projected in the sky and provide information about the angular distance. "Line-of-sight" (or "radial") BAOs require very precise redshifts, but provide a direct measurement of the Hubble parameter at different redshifts, a more sensitive probe of DE. The main goal of this paper is to show that it is possible to obtain photometric redshifts with enough precision (σz) to measure BAOs along the line of sight. There is a fundamental limitation as to how much one can improve the BAO measurement by reducing σz . We show that σz ~ 0.003(1 + z) is sufficient: a much better precision will produce an oversampling of the BAO peak without a significant improvement on its detection, while a much worse precision will result in the effective loss of the radial information. This precision in redshift can be achieved for bright, red galaxies, featuring a prominent 4000 Å break, by using a filter system comprising about 40 filters, each with a width close to 100 Å, covering the wavelength range from ~4000 to ~8000 Å, supplemented by two broad-band filters similar to the Sloan Digital Sky Survey u and z bands. We describe the practical implementation of this idea, a new galaxy survey project, Physics of the Accelerating Universe (PAU): http://www.ice.cat/pau, to be carried out with a telescope/camera combination with an etendue about 20 m2 deg2, equivalent to a 2 m telescope equipped with a 6 deg2 field of view camera, and covering 8000 deg2 in the sky in four years. We expect to measure positions and redshifts for over 14 million red, early-type galaxies with L > L* and i(AB) ~ 10–3 Mpc–3 h3 galaxies within the 9 Gpc3 h–3 volume to be sampled by our survey, ensuring that the error in the determination of the BAO scale is not limited by shot noise. By itself, such a survey will deliver precisions of order 5% in the dark-energy equation of state parameter w, if assumed constant, and can determine its time derivative when combined with future cosmic microwave background measurements. In addition, PAU will yield high-quality redshift and low-resolution spectroscopy for hundreds of millions of other galaxies, including a very significant high-redshift population. The data set produced by this survey will have a unique legacy value, allowing a wide range of astrophysical studies., This work was carried out in the framework of the PAU Consolider Collaboration, supported in part by the Spanish Ministry of Education and Science (MEC) through the Consolider Ingenio-2010 program, under project CSD2007-00060 "Physics of the Accelerating Universe (PAU)". Additional support comes from the Barcelona Supercomputer Center, as well as from the European Commission, the Spanish High Council for Scientific Research (CSIC), and the regional governments of Andalusia, Aragon, Catalonia, Madrid, and Valencia.

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.