Determining atmospheric aerosol content with an infra-red radiometer

TL;DR

This paper explores using an infra-red radiometer to measure atmospheric aerosol content by analyzing sky brightness temperature, providing a systematic, telescope-independent method for assessing sky clarity relevant for Cherenkov astronomy.

Contribution

It introduces a novel approach to quantify aerosol contribution to sky brightness temperature using an infra-red radiometer, independent of telescope systematics.

Findings

Aerosol contribution can reach up to 30 W/m² in emission profile.

Sky brightness temperature correlates with aerosol content and telescope trigger rates.

Method offers a systematic way to assess sky clarity for atmospheric monitoring.

Abstract

The attenuation of atmospheric Cherenkov photons is dominated by two processes: Rayleigh scattering from the molecular component and Mie scattering from the aerosol component. Aerosols are expected to contribute up to 30 Wm$^{-2}$ to the emission profile of the atmosphere, equivalent to a difference of $\sim20^\circ$C to the clear sky brightness temperature under normal conditions. Here we investigate the aerosol contribution of the measured sky brightness temperature at the H.E.S.S. site; compare it to effective changes in the telescope trigger rates; and discuss how it can be used to provide an assessment of sky clarity that is unambiguously free of telescope systematics.