Commissioning of the ATLAS Experiment

The ATLAS experiment based at the CERN Laboratory in Switzerland is expected to be one of the key experiments of its generation. Its results will help elucidate such fundamental questions of physics as the origin of mass and the existence of dark matter in the universe. After 15 years of design, fabrication, and installation, ATLAS is ready to collect first data from the high-energy proton collisions of the Large Hadron Collider (LHC). The commissioning of the ATLAS detector is a critical step in attaining these physics goals. Details are provided here on the status of the ATLAS experiment in September of 2008, just after having observed first beams in the LHC.