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Paper: NOAO/IRAF's ``Save The Bits'' - A Pragmatic Data Archive
Volume: 61, Astronomical Data Analysis Software and Systems III
Page: 119
Authors: Seaman, Rob
Abstract: Archival data has been pivotal to astronomy throughout history. Without Tycho's carefully recorded observations, Kepler's insight into the elliptical nature of the orbits of the planets would not have been possible. In our lifetime, the Palomar Sky Survey has been scrutinized daily for four decades by thousands of pairs of eyes. However, for a variety of reasons ground-based optical observatories have been late-comers, by and large, to the archiving of digital images. The era of the CCD has been one of data diaspora. Many of the impediments to creating an archive are peripheral to any archive's principal mission of saving the information for future generations. There is a moral imperative to do at least this much. Modern computer networks now provide the tools to build an image archive that is pragmatic both in terms of programming effort and cost. The NOAO ``Save The Bits'' archive described is now nightly (and daily) automatically archiving the raw data from a half dozen Kitt Peak telescopes via the ICE (IRAF Control Environment) data acquisition software. As images are acquired at each telescope using IRAF/ICE, a unique identifying string constructed from the telescope name, the date, and the UT of the observation is edited into each image header. The IRAF wfits task translates the images to FITS from within the ICE postprocessing script. A print spooler ( e.g. , Unix lpr / lpd ) provides a secure mechanism for transferring the FITS files across the network to a central archive server where they are queued for processing. The data from several telescopes are multiplexed onto a single archive medium ( e.g. , exabyte). As the FITS files are processed by the queue software, each is now stamped with a running sequence number and the resulting FITS header is appended to a catalog file, cross-referenced to the archive tape index. To promote efficient I/O, the individual images are concatenated into FITS Image Extension tape files several tens of Megabytes in size. A minilanguage tape monitor program (similar to lpc ) provides a screen oriented status display that may be run from any of the domes, or from a privileged account when swapping full archive tapes. The Save The Bits design would be straightforward to adapt to other projects.
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