FIRMOS-B results from the HEMERA3 stratospheric campaign

The Far-Infrared Radiation Mobile Observation System Balloon version (FIRMOS-B) is a spectroradiometer developed to provide FORUM-like measurements from a stratospheric platform. FIRMOS-B aims to collect FIR stratospheric nadir-looking data to test cloud parameters databases (e.g., single scattering databases) and spectroscopic databases, as well as to test FORUM retrievals. As part of the HEMERA project, FIRMOS-B flew aboard a stratospheric balloon launched by CNES from the CSA Timmins Stratospheric Balloon Base (Ontario, Canada), on 23 August 2022. Although the flight was troubled by instabilities and the measurements were disturbed by interferences, some valuable data were nevertheless obtained. FIRMOS-B was also tested on ground, before and after the HEMERA campaign, to check its performance in terms of NESR and spectral accuracy.This paper describes the instrument design, the campaign activities, and the acquired results. We will outline the specific design choices and the instrument characterization. We will also focus on the spectral data measured during the flight and on the higher-level geophysical products obtained by three independent analysis codes (KLIMA, FARM and SACR).