A case study in adaptable and reusable infrastructure at the Keck Observatory Archive: VO interfaces, moving targets, and more

摘要

This paper describes how the Keck Observatory Archive (KOA) is extending opensource software components to develop new services. In August 2015, KOAdeployed a program interface to discover public data from all instrumentsequipped with an imaging mode. The interface complies with version 2 of theSimple Imaging Access Protocol (SIAP), under development by the InternationalVirtual Observatory Alliance (IVOA), which defines a standard mechanism fordiscovering images through spatial queries. The heart of the KOA service is anR-tree-based, database-indexing mechanism prototyped by the VirtualAstronomical Observatory (VAO) and further developed by the Montage ImageMosaic project, designed to provide fast access to large imaging data sets as afirst step in creating wide-area image mosaics. The KOA service uses theresults of the spatial R-tree search to create an SQLite data database forfurther relational filtering. The service uses a JSON configuration file todescribe the association between instrument parameters and the service queryparameters, and to make it applicable beyond the Keck instruments. The R-tree program was itself extended to support temporal (in addition tospatial) indexing, in response to requests from the planetary science communityfor a search engine to discover observations of Solar System objects. With this3D-indexing scheme, the service performs very fast time and spatial matchesbetween the target ephemerides, obtained from the JPL SPICE service. Ourexperiments indicate these matches can be more than 100 times faster than whenseparating temporal and spatial searches. Images of the tracks of the movingtargets, overlaid with the image footprints, are computed with a newcommand-line visualization tool, mViewer, released with the Montagedistribution. The service is currently in test and will be released in Fall2016.