Measurements of Precipitable Water Vapour for the Africa Millimetre Telescope

Abstract

Precipitable Water Vapour (PWV) is the main source of opacity in millimetre and sub-millimetre observations. Thus, before establishing a millimetre or sub-millimetre observatory, evaluating the PWV above the location is crucial. This paper presents the results of ongoing measurements of PWV in two potential locations for the Africa Millimetre Telescope (AMT), using ground-based instruments available on site namely, AErosol RObotic NETwork (AERONET) and Autonomous Tool for Measuring Observatory site COnditions PrEcisely (ATMOSCOPE) and the H.E.S.S. weather stations. All measurements were taken at the High Energy Stereoscopic System (H.E.S.S.) observatory and for Mt. Gamsberg, PWV was estimated using the scaling method. The preliminary findings of this study show that the H.E.S.S. site has a slightly higher yearly median PWV than the former site of the SEST telescope at La Silla, with Mt. Gamsberg reaching even lower values by scaling to its elevation. However, in-situ measurements are recommended to validate the scaled results.