  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 sub-systems. 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.
