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

Metadata Enrichment for Digital Preservation

Description of structural and semantic relationships and properties of, within, and between resources is seen as a key issue in digital preservation. But the markup languages used to encode descriptions for migration between and storage within digital repositories are subject to the same interpretive problems that complicate other uses of markup. This paper reports on a project that aims to address these problems by explicating facts that otherwise would not support automated inferencing. These facts are expressed as RDF [Resource Description Framework] triples, stored in and retrieved from a scalable RDF-based repository.Library of Congress, award number A6075published or submitted for publicationis peer reviewe

Preserving Meaning, Not Just Objects: Semantics and Digital Preservation

The ECHO DEPository project is a digital preservation research and development project funded by the National Digital Information Infrastructure and Preservation Program (NDIIPP) and administered by the Library of Congress. A key goal of this project is to investigate both practical solutions for supporting digital preservation activities today, and the more fundamental research questions underlying the development of the next generation of digital preservation systems. To support on-the-ground preservation efforts in existing technical and organizational environments, we have developed tools to help curators collect and manage Web-based digital resources, such as the Web Archives Workbench (Kaczmarek et al., 2008), and to enhance existing repositories??? support for interoperability and emerging preservation standards, such as the Hub and Spoke Tool Suite (Habing et al., 2008). In the longer term, however, we recognize that successful digital preservation activities will require a more precise and complete account of the meaning of relationships within and among digital objects. This article describes project efforts to identify the core underlying semantic issues affecting long-term digital preservation, and to model how semantic inference may help next-generation archives head off long-term preservation risks.published or submitted for publicatio

6.14 1. BACKGROUND

Most of the best known and most extensive of the WWW servers that offer weather information products started as a single page listing and expanded from there to the detailed multi-page collections that they are today. Such was the case with the sections of the University of Illinois at Urbana-Champaign Department of Atmospheric Sciences ’ servers. Excluding the sections that offered educational material and the widely successful interactive weather map tools, the rest of the sections offering the bulk of the weather products however, unfortunately fell into disarray...victims of uncoordinated growth and the ultimately unmanageable underlying structures that supported them. So armed with experiences, successes, failures, and lots of wishlist items, we started out with a clean slate and undertook the design of a completely new weather server in order to “do it right this time.” The following details the design process and goals of the Weather World 2010 ™ server project. (Because much of the implementation of this design was still in progress (and flux) at the time of this writing, details of the actual implementation will be presented at a later date.