Calibration of the LIGO detectors for the First LIGO Science Run

We describe the calibration procedures applied to the data taken by the three LIGO interferometric gravitational wave detectors in the LIGO Science Collaborations First Science Run, from 23 August to 9 September 2002. The calibration depends on corrections to feedback servos used in the instrument, and on changing optical gains. We describe the stability of the calibration and detector sensitivity during the 17-day run.