PT Journal AU Pierre Auger Collaboration (Abraham, Jea Pastor, S TI The fluorescence detector of the Pierre Auger Observatory SO Nuclear Instruments & Methods in Physics Research A JI Nucl. Instrum. Methods Phys. Res. A PY 2010 BP 227 EP 251 VL 620 IS 2-3 DI 10.1016/j.nima.2010.04.023 LA English DE Cosmic rays; Fluorescence detector AB The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions. ER