  We have developed a framework for the Monte-Carlo simulation of the X-Ray
Telescopes (XRT) and the X-ray Imaging Spectrometers (XIS) onboard Suzaku,
mainly for the scientific analysis of spatially and spectroscopically complex
celestial sources. A photon-by-photon instrumental simulator is built on the
ANL platform, which has been successfully used in ASCA data analysis. The
simulator has a modular structure, in which the XRT simulation is based on a
ray-tracing library, while the XIS simulation utilizes a spectral
"Redistribution Matrix File" (RMF), generated separately by other tools.
Instrumental characteristics and calibration results, e.g., XRT geometry,
reflectivity, mutual alignments, thermal shield transmission, build-up of the
contamination on the XIS optical blocking filters (OBF), are incorporated as
completely as possible. Most of this information is available in the form of
the FITS (Flexible Image Transport System) files in the standard calibration
database (CALDB). This simulator can also be utilized to generate an "Ancillary
Response File" (ARF), which describes the XRT response and the amount of OBF
contamination. The ARF is dependent on the spatial distribution of the
celestial target and the photon accumulation region on the detector, as well as
observing conditions such as the observation date and satellite attitude. We
describe principles of the simulator and the ARF generator, and demonstrate
their performance in comparison with in-flight data.
