Calibration Infrastructure for the GLAST LAT

Abstract

The GLAST LAT calibration infrastructure is designed to accommodate a wide range of time-varying data types, including at a minimum hardware status bits, conversion constants, and alignment for the GLAST LAT instrument and its prototypes. The system will support persistent XML and ROOT data to begin with; other physical formats will be added if necessary. In addition to the "bulk data", each data set will have associated with it a row in a rdbms table containing metadata, such as timestamps, data format, pointer to the location of the bulk data, etc., which will be used to identify and locate the appropriate data set for a particular application. As GLAST uses the Gaudi framework for event processing, the Calibration Infrastructure makes use of several Gaudi elements and concepts, such as conversion services, converters and data objects and implements the prescribed Gaudi interfaces (IDetDataSvc, IValidity, ..). This insures that calibration data will always be valid and appropriate for the event being processed. The persistent representation of a calibration dataset as two physical pieces in different formats complicates the conversion process somewhat: two cooperating conversion services are involved in the conversion of any single dataset.