CALIBRATION OF THE SENSITIVITY OF IMAGING ATMOSPHERIC CHERENKOV TELESCOPES USING A REFERENCE LIGHT-SOURCE

The sensitivity of an Imaging Atmospheric Cherenkov telescope is calib rated by shining, from a distant pulsed monochromatic light source, a defined photon flux onto the mirror. The light pulse is captured and r econstructed by the telescope in an identical fashion as real Cherenko v light. The intensity of the calibration Light pulse is monitored via a calibrated sensor at the telescope; in order to account for the low er sensitivity of this sensor compared to the Cherenkov telescope, an attenuator is inserted in the light source between the measurements wi th the calibrated sensor, and with the telescope. The resulting telesc ope sensitivities have errors of 10%, and compare well with other esti mates of the sensitivity. (C) 1997 Elsevier Science B.V.