Ron Rechenmacher

The Sloan Digital Sky Survey Photometric Camera

We have constructed a large-format mosaic CCD camera for the Sloan Digital Sky Survey. The camera consists of two arrays, a photometric array that uses 30 2048 × 2048 SITe/Tektronix CCDs (24 μm pixels) with an effective imaging area of 720 cm2 and an astrometric array that uses 24 400 × 2048 CCDs with the same pixel size, which will allow us to tie bright astrometric standard stars to the objects imaged in the photometric camera. The instrument will be used to carry out photometry essentially simultaneously in five color bands spanning the range accessible to silicon detectors on the ground in the time-delay–and–integrate (TDI) scanning mode. The photometric detectors are arrayed in the focal plane in six columns of five chips each such that two scans cover a filled stripe 25 wide. This paper presents engineering and technical details of the camera.

The Discovery of a Field Methane Dwarf from Sloan Digital Sky Survey Commissioning Data

We report the discovery of the coolest field dwarf yet known, selected as an unresolved object with extremely red colors from commissioning imaging data of the Sloan Digital Sky Survey. Its spectrum from 0.8 to 2.5 μm is dominated by strong bands of H2O and CH4. Its spectrum and colors over this range are very similar to those of Gl 229B, the only other known example of a methane dwarf. It is roughly 1.2 mag fainter than Gl 229B, suggesting that it lies at a distance of ~10 pc. Such a cool object must have a mass well below the hydrogen-burning limit of 0.08 M☉ and therefore is a genuine brown dwarf, with a probable mass in the range 0.015-0.06 M☉ for an age range of 0.3-5 Gyr.

The Discovery of a Second Field Methane Brown Dwarf from Sloan Digital Sky Survey Commissioning Data

We report the discovery of a second field methane brown dwarf from the commissioning data of the Sloan Digital Sky Survey (SDSS). The object, SDSS J134646.45-003150.4 (hereafter SDSS 1346-00), was selected because of its very red color and stellar appearance. Its spectrum between 0.8 and 2.5 µm is dominated by strong absorption bands of H2O and CH4 and closely mimics those of Gliese 229B and SDSS 162414.37+002915.6 (hereafter SDSS 1624+00), two other known methane brown dwarfs. SDSS 1346-00 is approximately 1.5 mag fainter than Gliese 229B, suggesting that it lies about 11 pc from the Sun. The ratio of flux at 2.1 µm to that at 1.27 µm is larger for SDSS 1346-00 than for Gliese 229B and SDSS 1624+00, which suggests that SDSS 1346-00 has a slightly higher effective temperature than the others. Based on a search area of 130 deg2 and a detection limit of z*=19.8, we estimate a space density of 0.05 pc-3 for methane brown dwarfs with Teff approximately 1000 K in the 40 pc3 volume of our search. This estimate is based on small-sample statistics and should be treated with appropriate caution.

Pan-da And Beyond Data Acquisition For the Next Generation Experiments

We report on the status of the PAN-DA data acquisition system presented at the last Real Time Conference. Since that time, PAN-DA has been successfully used in the fixed target program at Fermilab. We also report on the plans and strategies for development of a new data acquisition system for the next generation of fixed target experiments at Fermilab. 10 refs., 3 figs.

The Low-Resolution Spectrograph of the Hobby-Eberly Telescope. II. Observations of quasar candidates from the Sloan Digital Sky Survey

ABSTRACT This paper describes spectra of quasar candidates acquired during the commissioning phase of the Low‐Resolution Spectrograph of the Hobby‐Eberly Telescope. The objects were identified as possible quasars from multicolor image data from the Sloan Digital Sky Survey. The 10 sources had typical r \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Lambda Station: On-Demand Flow Based Routing for Data Intensive Grid Applications Over Multitopology Networks

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The DZERO level 3 data acquisition system

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Data acquisition systems for the Sloan Digital Sky Survey

Lambda Station is an ongoing project of Fermi National Accelerator Laboratory and the California Institute of Technology. The goal of this project is to design, develop and deploy network services for path selection, admission control and flow based forwarding of traffic among data- intensive Grid applications such as are used in High Energy Physics and other communities. Lambda Station deals with the last-mile problem in local area networks, connecting production clusters through a rich array of wide area networks. Selective forwarding of traffic is controlled dynamically at the demand of applications. This paper introduces the motivation of this project, design principles and current status. Integration of Lambda Station client API with the essential Grid middleware such as the dCache/SRM Storage Resource Manager is also described. Finally, the results of applying Lambda Station services to development and production clusters at Fermilab and Caltech over, advanced networks such as DOEs UltraScience Net and NSFs UltraLight is covered.

artdaq: An event filtering framework for fermilab experiments

The DZERO experiment began RunII datataking operation at Fermilab in spring 2001. The physics program of the experiment requires the Level 3 data acquisition (DAQ) system system to handle average event sizes of 250 kilobytes at a rate of 1 kHz. The system routes and transfers event fragments of approximately 1-20 kilobytes from 63 VME crate sources to any of approximately 100 processing nodes. It is built upon a Cisco 6509 Ethernet switch, standard PCs, and commodity VME single board computers (SBCs). The system has been in full operation since spring 2002.

The Sloan Digital Sky Survey's use of the Web

The Sloan Digital Sky Survey will image (Pi) steradians about the north galactic cap in five filters, and acquire one million spectra using a dedicated 2.5 m telescope at the Apache Point Observatory in New Mexico. We describe the data acquisition system for the surveys three main detectors: an imaging camera, mounting 54 Tektronix charge-coupled devices (CCD); a pair of spectrographs, each mounting a pair of CCDs; and a smaller monitor telescope camera. We describe the systems hardware and software architecture, and relate it to the surveys special requirements for high reliability and need to understand its instrumentation in order to produce a consistent survey over a five year period.