ar X iv : a st ro - p h / 01 07 58 7 v 1 3 1 Ju l 2 00 1 1 THE INTEGRAL / IBIS TELESCOPE MODELING

The main objective of the IBIS modeling activities is the generation of the IBIS spectral response matrix. This generation will be done step by step by firstly constructing " calibrated model " of each IBIS subsystems. A " calibrated model " is defined as a GEANT Monte-Carlo model, further checked by intensive corresponding calibration. These calibrated models will be in a second step integrated in the whole IBIS Mass Model. This Mass Model will be checked and refined using the data obtained during the IBIS Telescope calibration, the PLGC during the ETET period, and the In-flight calibration data acquired during the whole INTEGRAL mission. The IBIS Mass Model will be used also for computations of efficiencies and transparencies. Some imaging studies (such as the study of the diffuse emission) may be also done with the help of the IBIS Mass Model. The IBIS Mass Model may be used for the simulation of IBIS data in order to check the different IBIS software. 1. THE INTEGRAL SATELLITE AND ITS INSTRUMENTS INTEGRAL is a 15 keV-10 MeV γ-ray mission with concurrent source monitoring at X-rays (3-35 keV) and in the optical range (V, 500-600 nm). All instruments are coaligned and have a large FOV, covering simultaneously a very broad range of sources. The INTEGRAL payload consists of two main γ-ray instruments, the spectrometer SPI and the im-ager IBIS, and of two monitor instruments, the X-ray monitor JEM-X and the Optical Monitoring Camera OMC. The Imager on Board Integral Satellite (IBIS) provides diagnostic capabilities of fine imaging (12' FWHM), source identification and spectral sensitivity to both continuum and broad lines over a broad (15 keV–10 MeV) energy range. It has a continuum sensitivity of 2 10 −7 ph cm −2 s −1 at 1 MeV for a 10 6 seconds observation and a spectral resolution better than 7 % @ 100 keV and of 6 % @ 1 MeV. The imaging capabilities of the IBIS are characterized by the coupling of its source discrimination capability (angular resolution 12' FWHM) with a field of view (FOV) of 9 • × 9 • fully coded, 29 • × 29 • partially coded FOV. The spectrometer SPI will perform spectral analysis of γ ray point sources and extended regions with an unprecedented energy resolution of ∼ 2 keV (FWHM) at 1.3 MeV. Its large field of view (16 • circular) and limited angular resolution (2 • …