VERITAS is an array of four identical telescopes designed for detecting and measuring astrophysical gamma rays with energies in excess of 100 GeV. Each telescope uses a 12 m diameter mirror to collect Cherenkov light from air showers initiated by the incident gamma rays and direct it onto a `camera' comprising 499 photomultiplier tubes (PMTs) read out by flash ADCs. We describe here calibration methods used for determining the values of the parameters which are necessary for converting the digitized PMT pulses to gamma-ray energies and directions. Use of laser pulses and FADC baseline fluctuations to determine and monitor PMT gains are discussed, as are measurements of the absolute throughput of the telescopes using muon rings.

VERITAS

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 3 (OG part 2), pages 1417-1420