Streamlined calibration of the ATLAS Muon Spectrometer precision chambers

The ATLAS Muon Spectrometer is comprised of 1150 optically Monitored Drifttube Chambers (MDTs) containing 354,000 aluminum drift tubes. The chambers are configured in barrel and endcap regions. The momentum resolution required for the LHC physics reach (dp/p = 3% and 10% at 100 GeV and at 1 TeV respectively) demands rigorous MDT drift tube calibration with frequent updates. These calibrations (RT functions) convert the measured drift times to drift radii and are a critical component to the spectrometer performance. They are sensitive to the MDT gas composition: Ar 93%, CO₂ 7% at 3 bar, flowing through the detector at a rate of 100,000 l hr^-1. We report on the generation and application of Universal RT calibrations derived from an inline gas system monitor chamber. Results from ATLAS cosmic ray commissioning data are included. These Universal RTs are intended for muon track reconstuction in the LHC startup phase.