Far-infrared field instruments, observations, and data analysis at CNR-INO

This paper presents the research activities carried out by the SPHERES team (Spectroscopy and PHotonics for Environmental Research and Earth Studies) at CNR-INO (in Florence, Italy) to measure the Earth's longwave spectrum, from the far- to the mid- infrared. These measurements are fundamental for understanding the role of atmospheric constituents (such as water vapour, ozone, etc.), clouds and surface type, in the determination of the planet's radiation balance. We illustrate the experimental facilities designed and built at our institute. More specifically, we describe the REFIR-PAD spectroradiometer, which, after acquiring measurements in several ground-based and balloon-borne campaigns, since 2011, has been continuously measuring the downwelling longwave spectrum from the Concordia station in Antarctica. We also focus on the recently developed FIRMOS instrument that, since 2018, has been supporting the FORUM mission preparatory activities by acquiring measurements in dedicated ground-based and balloon-borne campaigns. Additionally, we introduce new instruments currently under development with thesupport of national projects. We finally illustrate the key features of the tools developed at our premises for the retrieval of atmospheric, cloud and surface properties from the measured spectral radiances, with a focus on the datasets produced and on their possible exploitation to further support the FORUM mission.