SWAMM: Sounding of Water vapour by Attenuation Microwave Measurements

A critical problem in atmospheric remote sensing is to perform systematic water vapor (WV) measurements in the lowest part of the troposphere (~5-6 km) on a global scale, which helps to improve both climate modeling and numerical weather prediction capabilities at short time scale. An innovative approach (the Normalized Differential Spectral Attenuation-NDSA) has been proposed capable to estimate the integrated water vapour (IWV) along microwave links crossing the troposphere based on attenuation measurements made in the Ku/K bands. Two ESA studies provided an exhaustive insight into all theoretical aspects of the NDSA technique applied to the case of two counter-rotating LEO satellites. The 2-years long SWAMM project, started in 2016 and funded by Tuscany Region, aims at implementing an instrument able to perform NDSA measurements at 19 GHz between a transmitter at ground and a receiver onboard a stratospheric platform. The features of the NDSA instrumentation (low cost, small weight and size) and the advantages brought by NDSA measurements in the configuration illustrated below make this approach particularly attractive for being exploited in Earth-HAPS links.