The Dark Energy Survey Data Management System

The Dark Energy Survey collaboration will study cosmic acceleration with a 5000 deg2 griZY survey in the southern sky over 525 nights from 2011-2016. The DES data management (DESDM) system will be used to process and archive these data and the resulting science ready data products. The DESDM system consists of an integrated archive, a processing framework, an ensemble of astronomy codes and a data access framework. We are developing the DESDM system for operation in the high performance computing (HPC) environments at NCSA and Fermilab. Operating the DESDM system in an HPC environment offers both speed and flexibility. We will employ it for our regular nightly processing needs, and for more compute-intensive tasks such as large scale image coaddition campaigns, extraction of weak lensing shear from the full survey dataset, and massive seasonal reprocessing of the DES data. Data products will be available to the Collaboration and later to the public through a virtual-observatory compatible web portal. Our approach leverages investments in publicly available HPC systems, greatly reducing hardware and maintenance costs to the project, which must deploy and maintain only the storage, database platforms and orchestration and web portal nodes that are specific to DESDM. In Fall 2007, we tested the current DESDM system on both simulated and real survey data. We used Teragrid to process 10 simulated DES nights (3TB of raw data), ingesting and calibrating approximately 250 million objects into the DES Archive database. We also used DESDM to process and calibrate over 50 nights of survey data acquired with the Mosaic2 camera. Comparison to truth tables in the case of the simulated data and internal crosschecks in the case of the real data indicate that astrometric and photometric data quality is excellent.Comment: To be published in the proceedings of the SPIE conference on Astronomical Instrumentation (held in Marseille in June 2008). This preprint is made available with the permission of SPIE. Further information together with preprint containing full quality images is available at http://desweb.cosmology.uiuc.edu/wik

LSST: from Science Drivers to Reference Design and Anticipated Data Products

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

Piezo-Electric And Viscoelastic Control Of Lifting Surface Aerodynamic Derivatives And Aileron Reversal

The present study is part of a series of systematic fundamental investigations into the e#ects of damping arising from piezo-thermo-viscoelasticity to control and minimize undesirable flexible structural contributions in flight vehicles. Previous research (Beldica et al. 1998a, b; Hilton &amp; Yi 1998) has demonstrated through computer simulations the attractive performance of piezoelectric viscoelastic devices to control aerodynamic noise, divergence and flutter. The present study evaluates time dependent aileron e#ectiveness and reversal and aerodynamic derivatives and their control through piezoelectric viscoelastic devices in viscoelastic lifting surfaces. The ultimate aim of these research e#orts is formulate and evaluate piezo-electro-viscoelastic control of actual high temperature metal and/or composite flight structures through massively parallel computations. The theory of aeroelasticity is well established and may be found described in detail in such classical texts as Bisplingho..

Piezoelectric Control Of Linear Viscoelastic Composite Columns -- Creep Buckling And Delamination

An analysis and computational simulations are carried out for the creep buckling and stochastic delamination onset failures of viscoelastic columns under piezoelectric control. Creep buckling times and probabilities of failure are determined and design criteria based on divergence times and/or times to reach preassigned levels of failure probabilities are examined. It is shown that piezoelectric control can be e#ectively used to delay, but not eliminate, creep buckling and delamination onset. Since the failure theories consider the combined effects of bending, shear, compression and normal interlaminar stresses, delamination onset is predicted at smaller axial loads than the critical buckling loads in the elastic case and at shorter viscoelastic lifetimes. KEY WORDS: computational solid mechanics, creep buckling, damping, piezo-viscoelasticity, probability of failure, structural control. 1 INTRODUCTION Column creep buckling received early attention by Hilton (1952) and Libove (1952) ..

Analytical Simulations Of Optimum Anisotropic Linear Viscoelastic Damping Properties

Analytical formulations based on material responses of &quot;anisotropic viscoelastic designer materials&quot; developed in the present paper prescribe what type of optimal anisotropic viscoelastic materials are to be manufactured to meet specific service requirements of loading, moisture and temperatures for quasi-static and time dependent environments. Keywords : anisotropic viscoelasticity, composites, damping, designer materials, optimal material characterization, structural control, volume fractions. INTRODUCTION In a previous paper (Hilton &amp; Yi 1992), a systematic study was undertaken to determine how shapes of relaxation--time functions a#ect damping characteristics of isotropic viscoelastic materials. The significant parameters were the instantaneous and fully relaxed moduli (Regions A and E on Fig. 1), the two &quot;knees&quot; (B and D), the central slope (C) and anisotropic shift functions. The sensitivity of these parameters is not of equal strength in their e#ect on material damping cha..

Piezoelectric And Viscoelastic Control Of Lifting Surface Aerodynamic Derivatives And Aileron Reversal

The e#ects of viscoelastic piezoelectric damping on the control of aerodynamic derivatives and of aileron reversal time retardation is formulated and evaluated. It is shown that significant control can be achieved with devices which add insignificant weight to flight vehicles, i. e. creep divergence and aileron reversal can be delayed in time. Keywords : aerodynamic derivatives, aeroviscoelasticity, aileron and elevator reversal, control, damping, divergence, piezo-electro-viscoelasticity, viscoelasticity. INTRODUCTION The present study is part of a series of systematic fundamental investigations into the e#ects of damping arising from piezo-thermo-viscoelasticity to control and minimize undesirable flexible structural contributions in flight vehicles. Previous research (Beldica et al. 1998a, b; Hilton &amp; Yi 1998) has demonstrated through computer simulations the attractive performance of piezoelectric viscoelastic devices to control # Copyright c # 1999 by the authors. Published ..