Alignment of the ATLAS Inner Detector Tracking System

The ATLAS experiment is equipped with a tracking system for c harged particles built on two technologies: silicon and drift tube base detectors. These kind of detectors compose the ATLAS Inner Detector (ID). The Alignment of the ATLAS ID tracking s ystem requires the determination of almost 36000 degrees of freedom. From the tracking point o f view, the alignment parameters should be know to a few microns precision. This permits to att ain optimal measurements of the parameters of the charged particles trajectories, thus ena bling ATLAS to achieve its physics goals. The implementation of the alignment software, its framewor k and the data flow will be discussed. Special attention will be paid to the recent challenges wher e large scale computing simulation of the ATLAS detector has been performed, mimicking the ATLAS o peration, which is going to be very important for the LHC startup scenario. The alignment r esult for several challenges (real cosmic ray data taking and computing system commissioning) will be also reported.