Night sky background measurements by the Pierre Auger fluorescence detectors and comparison with simultaneous data from the UVscope

THE PIERRE AUGER COLLABORATION (AUTOR 434 DE 474); M. TUEROS (COAUTOR)

Beijing

Conferencia; 32nd International Cosmic Ray Conference 2011; 2011

Institute of High Energy Physics, Chinese Academy of Sciences

Due to the AC coupling of PMTs in the Pierre Auger Fluorescence Detectors, the slowly varying current induced by the Night Sky Background cannot be directly measured. Estimate of the Night Sky Background is however indirectly obtained by the statistical analysis of the current fluctuations, whose variance is recorded every 30 s for each pixel. We present the procedure used to convert the raw background data of the Fluorescence Detector to an absolute calibrated Night Sky Background flux and compare the results with data taken simultaneously with the UVscope instrument (a single photon counting UV detector) placed on the roof of one of the Fluorescence Detector buildings. We also show how the measurements of Night Sky Background flux can effectively be used as a general non-invasive tool to verify the end-to-end calibration of a large aperture telescope with multi-pixel cameras.