The Earth's surface temperature is a key parameter for the understanding of the energetic and hydrological balance of the Earth. Continuous measurements of the global temperature distribution provide information on its changes and impact on theglobal climate.With the BIRD small satellite mission (size: 158 cm×64 cm×52 cm, mass: 85 kg) a new generation of imaging infrared sensors to be used in space will be tested [1]. The main scientific tasks include the developing of temperature retrieval methods forhigh-temperature-events like fires, vulcanos etc. as well as for "normal" Earth's surface temperature like the temperature of vegetation, etc. - the fire surrounding temperature. BJRD, a multi-spectral sensor system, is slated to be launched in 2000. Itconstists of two IR cameras (3.4 - 4.2μm (MIR -Mid InfraRed) and 8.5 - 9.3μm (TIR -Thermal InfraRed)) as well as a stereo camera WAOSS (Wide-Angle Optoelectronic Stereo Scanner) where the spectral ranges lie within the visible (VIS) and the nearinfrared (NIR).Two temperature retrieval methods customized for the BIRD channel constellation are established. One method is based on a multi-spectral regression (refered to as "regression"-approach) using brightness temperatures of both channels at the top of theatmosphere. The other approach recovers land surface emissivity and temperature from ground radiances utilizing a "Temperature Independent Spectral Index for Emissivity" (refered to as "TISIE"-approach) [2]. Both methods lead to equivalent temperatureretrieval errors, but the "TISIE"-approach does not need an a priori knowledge of the emissivity.
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