Measurement of atmospheric transparency in Telescope Array using Central Laser Facility

Abstract

The Telescope Array (TA) experiment has three fluorescence detector(FD) stations to de-tect fluorescence emission by extensive air showers induced by Ultra High Energy Cosmic Rays(UHECRs). These fluorescence light is attenuated and lost by aerosols in the atmosphere through the path of propagation to the FD. Calibration of atmospheric attenuation is necessary to estimate the energy of cosmic ray. The Central Laser Facility (CLF) consists of a laser that fires a 355 nm burst vertically with 10 Hz, every half-hour. The Vertical Aerosol Optical Depth(VAOD) which is atmospheric transparency can be measured every 30 minutes by the CLF. Therefore, we can monitor the change of the atmosphere every 30 minutes within the FD observation time. The CLF is located at the center of three FD stations and observes the atmospheric transparency of the TA site. We report the results of atmospheric transparency at the TA site.