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C.R. Shrader, S.J. Sturner, B.J. Teegarden (NASA/GSFC)
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is an ESA managed mission scheduled for a 2001 launch. One of its primary experiment packages, the INTEGRAL Spectrometer or "SPI", is a high-resolution cooled-germanium instrument. It covers the approximate 20 keV to 10 MeV energy range with an energy resolution of about 500. This presentation offers a brief overview of SPI and its anticipated capabilities, with an emphasis Monte Carlo simulations and exploration of data analysis techniques being carried out at the NASA Goddard Space Flight Center (GSFC). GSFC is one of the SPI consortium institutions; primary responsibilities for the building and testing of the instrument reside with CESR and CNES in France and MPE in Germany. We describe our current model of the instrument and present some results of our simulations. Methods of data analysis being explored by our group are discussed. The unique nature of the instrument, 19 separate detector elements viewing the sky through a coded mask aperture, poses a number of difficulties. For example, a typical observation consists of multiple pointings (following a predefined dithering pattern) with an instrument response that is highly directionally dependent. Multiple sources are often likely to be contained within the nominal 15-degree FoV, and most high-energy point sources are variable over observable timescales. Each of the detectors may have individual characteristics as well, thus a typical deconvolution of the detector count-rate data involves a complex global minimization problem over large data and parameter spaces. Strategies for dealing with these difficulties, which are under exploration by our group in collaboration with other SPI consortium institutions, are discussed and some preliminary results based on simulated data are presented. From these results, some insight into the anticipated capabilities of SPI, and speculation on its scientific impact is offered.
The author(s) of this abstract have provided an email address for comments about the abstract: shrader@grossc.gsfc.nasa.gov