Polar Radiant Energy in the Far InfraRed Experiment (PREFIRE) Spectral Flux from PREFIRE Satellite 1 (PREFIRE_SAT1_2B-FLX) contains surface emissivity derived from data collected by the PREFIRE Thermal Infrared Spectrometer (TIRS-PREFIRE) aboard PREFIRE-SAT1. Dual CubeSats each carry a PREFIRE Thermal Infrared Spectrometer (TIRS-PREFIRE), a push broom spectrometer with 63 channels measuring mid- and far-infrared (FIR) radiation from approximately 5 to 53 µm. Most polar emissions are in the FIR but have not been measured on a large scale. PREFIRE aims to fill knowledge gaps in the global energy budget by more accurately characterizing polar emissions. This information will then be assimilated into global circulation and other models to predict future conditions more accurately.PREFIRE_SAT1_2B-FLX contains spectral flux at the top of atmosphere for all available TIRS-PREFIRE channels as derived from PREFIRE Spectral Radiance (PREFIRE_SAT1_1B-RAD) data using an Optimal Estimation retrieval with inputs from the PREFIRE_SAT1_2B-MSK (cloud mask), PREFIRE_SAT1_AUX-MET (Auxiliary Meteorology), and PREFIRE_SAT1_AUX-SAT collections. PREFIRE_SAT1_2B-FLX also contains the top-of-atmosphere Outgoing Longwave Radiation (OLR) broadband flux. The primary purpose of this collection is to assess the radiative activities over the polar regions to better quantify the energy budget there.Science data retrieval started July 24, 2024 and is ongoing. Geographic coverage is global, with the greatest concentration of data in the polar regions. Within the orbital swath there are eight distinct tracks of data associated with the eight separate spatial scenes for each PREFIRE-TIRS. At the beginning of the mission, the approximate scene footprint sizes were 11.8 km x 34.8 km (cross-track x along-track), with gaps between each scene of approximately 24.2 km. The entire swath was ~264 km across. Note that the scene footprint and swath sizes quoted here are for the orbit altitude soon after launch. However, the footprint size will slowly become smaller as the orbit altitude decreases with time. This data has a temporal resolution of 0.707 seconds and is available in netCDF-4.The spectral flux data for the sister instrument aboard PREFIRE-SAT2 can be found in the PREFIRE_SAT2_2B-FLX collection.