Abstract Details

Name: Mani Khurana
Affiliation: Bhabha Atomic Research centre
Conference ID: ASI2021_227
Title : Feasibility study of Duty cycle for MACE gamma-ray Telescope under partial Moonlit.
Authors and Co-Authors : M. Khurana, S. Godiyal, K. K. Singh, K. K. Yadav (Astrophysical Sciences Division, Bhabha Atomic Research Centre, Mumbai-400085)
Abstract Type : Oral
Abstract Category : Instrumentation and Techniques
Abstract : Major Atmospheric Cherenkov Experiment (MACE) is a ground-based gamma-ray telescope recently installed 4.3 km above sea level, Hanle, Ladakh. The MACE telescope equipped with a 21 meter diameter light reflector and an imaging camera with 1088 pixels (photo-multiplier tubes) at the focal plane, is expected to explore the gamma-ray Universe in the energy range 20 GeV to 5 TeV. The imaging Cherenkov telescopes like MACE are generally operated during clear and moonless dark nights to avoid the damage of photo-multiplier tubes due to excessive light. As, astronomical observational site, Hanle provides about 260 spectroscopic clear nights per year for gamma-ray observations. Therefore, the duty cycle of telescope is limited to about 18%. In this work, we present the results from a feasibility study of operating the MACE telescope under partial moon-light conditions which lead to a very significant enhancement in the effective duty cycle up to about 30% per year. We use a model for moon brightness to estimate the total light of night sky flux in the wavelength range 300-700 nm. The light of night sky flux is convoluted with the wavelength dependent mirror reflectivity and quantum efficiency of photo-multiplier tubes to estimate the anode current as function of moon-phase for a given angular separation between a gamma-ray source and the moon. Details of the effect of increase in the anode current on the operating parameters of MACE telescope under relaxed partial moonlit conditions will be presented.