  The Pierre Auger Observatory in Malargue, Argentina, is designed to study the
origin of ultrahigh energy cosmic rays with energies above 10^18 eV. The energy
calibration of the detector is based on a system of four air fluorescence
detectors. To obtain reliable calorimetric information from the fluorescence
stations, the atmospheric conditions at the experiment's site need to be
monitored continuously during operation. One of the components of the
observatory's atmospheric monitoring system is a set of four elastic
backscatter lidar stations, one station at each of the fluorescence detector
sites. This paper describes the design, current status, standard operation
procedure, and performance of the lidar system of the Pierre Auger Observatory.
