The status of the simulation project for the ATLAS experiment in view of the LHC startup

The Simulation suite for ATLAS is in a mature phase, ready to cope with the challenge of the 2009 data. The simulation framework, which is integrated to the ATLAS framework (Athena) offers a set of pre-configured applications for the full simulation of ATLAS, combined test beam setups, cosmic ray setups and old standalone test-beams. Each detector component has been carefully described in detail and monitored for performance. The few pieces of the apparatus (forward and very forward detectors), inert material and services (toroid supports, support rails, detector feet) that are still missing are about to be integrated in the current simulation suite. Detailed descriptions of the ideal and real geometries for each ATLAS subcomponent allow optimization studies and validation. Small scale productions are monitored daily through a set of tests for different samples of physics events, and large scale productions on the Grid verify the robustness of the implementation as well as possible errors only visible on large statistics. The conditions used in the simulation process are now stored in the output file as metadata, and can be utilized to process the data properly. A fast shower simulation suite has also been developed in ATLAS and performance comparisons are part of the overall evaluation.