  Large-scale computing in ATLAS is based on a grid-linked system of tiered
computing centers. The ATLAS Great Lakes Tier-2 came online in September 2006
and now is commissioning with full capacity to provide significant computing
power and services to the USATLAS community. Our Tier-2 Center also host the
Michigan Muon Calibration Center which is responsible for daily calibrations of
the ATLAS Monitored Drift Tubes for ATLAS endcap muon system. During the first
LHC beam period in 2008 and following ATLAS global cosmic ray data taking
period, the Calibration Center received a large data stream from the muon
detector to derive the drift tube timing offsets and time-to-space functions
with a turn-around time of 24 hours. We will present the Calibration Center
commissioning status and our plan for the first LHC beam collisions in 2009.
