Absolute and Multiwavelength calibration of the Pierre Auger Observatory fluorescence detectors

The methods and results of the calibration of the Pierre Auger Observatory fluorescence detectors will be presented. Two methods are shown, an absolute calibration at a single UV wavelength and a relative calibration at several UV wavelengths. Both techniques use a uniform 2.5m diameter light source and are an end-to-end measurement of all the detector components. This technique calibrates the combined effect of each component in a single measurement. Recent improvements in technique and equipment have increased calibration reliability and improved uncertainties. We discuss these improvements here, including digital control and monitoring of LED pulses, a technique using the $1/r^2$ attenuation of light in the calibration of this low intensity light source, and the use of a monochromator to pick out single wavelengths in a broad UV range to perform the multiwavelength calibration.