15 years of Level-2 analysis of FORUM-like observations

In the last 15 years, we performed scientific feasibility studies for the FORUM mission and Level-2 data analysis of observations made by some FORUM-like instruments. A review of all the results of the Level-2 analysis are here briefly presented. For these activities, we have employed the KLIMA (Kyoto protocoL Informed Management of the Adaptation) code. The code KLIMA is a tool able both to compute the atmospheric spectrum in the infrared spectral region and to analyse the observations to obtain information on the minor atmospheric constituents and surface characteristics. The first results were obtained from the analysis of the RERIR-PAD measurements acquired during the measurement campaign where the instrument was launched onboard of a stratospheric balloon near Teresina (Brazil 2005). From these measurements, the ability to obtain information on the vertical profiles of water vapour and temperature was demonstrated, furthermore the improvements in the far infrared obtained in the HITRAN spectroscopic database (from 2000 to 2004) were compared and evaluated. Subsequently, the Zugspitze ground measurement campaign (Zugspitze Observatory 2019) was analysed carrying out the validation of Level-2 products and the characterization of the instrumental errors. Finally, the measurements acquired by the FIRMOS-B instrument during the ground-based test campaigns (Florence 2022 and 2023) and during the HEMERA stratospheric balloon campaign (Timmins, Canada 2022) were used to perform the instrumental characterization in terms of instrumental spectral response function, channels position, noise equivalent spectral response and calibration error. KLIMA code is shown to be adequate to perform the analysis of FORUM-like measurements from different platforms, which in turn demonstrated the high performance of FORUM mission.