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Дата изменения: Fri Oct 13 00:29:10 2000 Дата индексирования: Tue Oct 2 06:41:37 2012 Кодировка: Поисковые слова: ultraviolet |
The Space Telescope Science Institute (STScI) holds the Hubble Data Archive (HDA), which includes all Hubble Space Telescope (HST) observations. The HDA, as of November 1999, contains over 7 TB of science and engineering data, for a total of science exposures. In the past year the volume of archived data has reached average rates of about 4 GB/day, with GB/day retrieved by archive users.
Based on the success of the HDA, and taking advantage of its existing archive infrastructure, the STScI archive has taken on responsibilities as NASA's UV/optical/near-IR archive center and has recently expanded by providing access to non-HST data. The Multimission Archive at the Space Telescope Science Institute (MAST) includes extreme ultraviolet, ultraviolet, and selected radio archives, all of which may be accessed at the MAST homepage.
The MAST holdings are available via simple World Wide Web (WWW) interfaces. A sample search page for IUE data is shown in Figure 1. Similar interfaces are available for all MAST data.
Archival data may be searched by name (resolved by SIMBAD or NED), position, object category, and observation specifics (date, instrument, filters, exposure time, etc.). Previews are available for most MAST missions, to allow the user to have a ``quick look'' at the data before retrieving them.
The potential use of the MAST archive is greatly increased by allowing users to search more than one mission at a time and cross-correlate the archive holdings with astronomical catalogs. Cross-correlations can be performed using the Hipparcos stellar catalog, an active galactic nuclei catalog, the Abell Galaxy Cluster catalog, and any user-supplied list of positions. MAST users can select a sample of astronomical sources based on a range of properties (e.g., redshift, magnitude, radio flux for active nuclei) and then look for the relevant entries in MAST. Work is in progress to expand this facility by using NASA's Astronomical Data Center (ADC) interface. This will allow cross-correlations to be made between MAST and any of the ADC catalogs and tables, opening up new possibilities for the exploitation of MAST data.
Most MAST data are now stored at STScI. (See Abney & Richon (2000) for a discussion of the HDA migration to magneto-optical media.) The MAST data network consists of a SUN Enterprise 450 server, a large staging disk area, and two Plasmon 480 platter CD-ROM jukeboxes. The migration of IUE data to STScI is now completed and only EUVE data are not stored on-site (they currently reside at HEASARC but are easily accessible through MAST).
Having most MAST data stored on-site allows direct data retrievals: selected data are retrieved simply by clicking on the data set name. No username or password is required. Data sets may be downloaded as .tar, .tar.gz, .tar.Z, or .zip files. MAST has made every attempt to include sufficient documentation and background information to make its data products as useful as possible. Each mission generally includes a project description, details of the data processing, data description (documentation, known problems, etc.), and information on available software for data reduction. MAST also is the prime software provider for many missions.
MAST will incorporate additional ultraviolet and optical archives in the future, particularly those connected with NASA's missions. MAST will further enhance the scientific value of its data holdings by seeking to archive data from ground-based CCD mosaic imagers. Work is in progress to link HST datasets with the publications which resulted from them. This will allow archival researchers to have easy access to all HST-based papers from the HST WWW interface. To fully exploit the multiwavelength parameter space which is being made available also by the many large surveys completed and under way, MAST will establish closer ties and coordination with other archive centers. Within this framework, MAST will work towards providing the community with ``science-ready'' products. For example, data characterization and catalogs of selected HST data would enable the identification of faint optical counterparts of deep surveys at various wavelengths.
STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NAG5-7584 and by other grants and contracts.
Abney, F. & Richon, J. 2000, this volume, 161