Hubble Space Telescope Primer for Cycle 11

7.2 The HST Data Archive

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All science and calibration data, along with a large fraction of the engineering data, are placed in the HST Data Archive. Science data become immediately available to a program's investigators, but do not become publicly available to other researchers until after the expiration of the proprietary period (see Section 5.1 of the Call for Proposals for information on data rights).

As of March 1, 2001, the Archive contained over 382,000 individual HST observations. These observations, along with engineering data and other supporting information, comprise approximately 7.0 Terabytes of data. About 160 new observations (and 5 Gbytes of data) are archived every day. The heart of the Archive is the Data Archive and Distribution Service (DADS)-a collection of magneto-optical disks on which the data are stored, the databases that comprise the Archive catalog, and the hardware and software that support the ingest and distribution of HST data.

7.2.1 StarView and Web Access to the HST Data Archive

Most of the data in the HST Archive are public and may be retrieved by any user. The Archive can be accessed either through the HST Data Archive Web Page or by using a special user interface, StarView. The Web page provides a fast means for doing simple searches for data in the Archive. Through the Archive Web interface, the user can retrieve data as well as the corresponding calibration and observatory monitoring files. StarView, available for most popular operating systems, is a JAVA-based interface suitable for more sophisticated searches of the Archive. It provides a wide variety of search options, including screens to review the calibration of observations and to search the text of HST observing proposal abstracts. Also, Starview allows the user to create custom queries and cross-correlate lists of targets with HST pointings. Search results may be examined in single-record or in table formats, and can be saved to a file.

The HST Archive and StarView allow you to preview most of the publicly available images and spectra. Both interfaces also offer integrated access to the Digitized Sky Survey (DSS) and allow the user to access the Set of Identifications, Measurements and Bibliography for Astronomical Data (SIMBAD) or NASA/IPAC Extragalactic Database (NED) to look up the coordinates of an object by name.

Archive users may use either StarView or the Web interface to request HST data. By the time Cycle 11 observations begin, all data requested from WFPC2, ACS, STIS, and NICMOS will be reprocessed in the pipeline at the time of the request. This On-The-Fly Reprocessing (OTFR) takes the science data in spacecraft packet format and generates calibrated files. On-The-Fly Reprocessing replaces On-The-Fly Calibration (OTFC). OTFR differs from OTFC by starting at an earlier stage in the data pipeline, and allows a clean integration of new headers with updated keywords which are fully compatible with the latest version of the pipeline and calibration software. As of the summer of 2000, the Archive ceased to save the initial versions of the calibrated data for STIS and WFPC2. The first version of the OTFR system will provide both raw and calibrated data files for all requests for science data.

Check the HST Data Archive Web Page for a complete listing of user services, and for detailed information on accessing data in the Archive, either through the Web interface or through StarView. The Starview Web Page provides access to the Starview software.

STScI maintains an "Archive Hotseat" to which all Archive-related questions, problems, or comments should be referred. The Archive Hotseat can be reached by email at archive@stsci.edu or by phone at 410-338-4547.