Study of the 30 THz atmospheric optical depth at El Leoncito

FERNANDO MARCELO LÓPEZ; GUILLERMO GIMENEZ DE CASTRO; RAULIN, JEAN-PIERRE

Congreso; Conferencia Latinoamericana de Geofísica Espacial; 2022

Mid-infrared solar observations were recently started with the ARgentine 30 THZ Telescope (AR30T) which has a spectral window centered at 30 THz (10 μm), between 7.5 μm and 14 μm. The knowledge of the atmospheric extinction is key to understanding how the solar radiation is absorbed by the terrestrial atmosphere, a fundamental aspect to interpret data obtained by ground-based telescopes. In this work we present the first results of the atmospheric absorption in the mid-infrared using data taken with AR30T. The instrument is located at an altitude of 2500 meters at the Estación de Altura Carlos U. Cesco (OAFA-UNSJ) in the National Park "El Leoncito" (San Juan, Argentina). The atmospheric optical depth (τ30) at 30 THz is determined by the solar extinction observed at different elevation angles, and a Levenberg-Marquardt least-squares technique is used to fit the atmospheric radiative transfer equation to the observations. Our findings indicate that "El Leoncito" would present low opacity at 30 THz, with values of τ30 of 0.04, 0.06 and 0.16 for the 50th, 75th and 90th percentiles respectively. Our analysis indicates very favorable conditions for mid-infrared observations from the observatory.