As with the previous BIRD satellite, the primary payload of the FireBIRD mission on the TET-1 and BIROS satellites was developed at the DLR Institute of Optical Sensor Systems. It consists of a bi-spectral infrared sensor, which records signals in the mid- and thermal-infrared spectral ranges (3.4-4.2 microns and 8.5–9.3 microns). An additional camera records three channels in the range of visible light through near-infrared. The first FireBIRD satellite, TET-1, was launched on 22 July 2012 as part of the On Orbit Verification (OOV-TET) mission of DLR’s Space Administration Division. The second satellite, BIROS, was launched on 22 June 2016 and is a copy of the TET-1 bus with construction financed by a grant from the Federal Ministry of Education and Research. At an altitude of approximately 570 km in sun-synchronous orbits the two satellites operate in a constellation which can be influenced to a certain extent by so-called “phasing” of BIROS. The purpose of FireBIRD is to explore and demonstrate the expanded possibilities offered by a satellite constellation for remotely sensing fires.