Calibration of the thermal band of the Landsat Multispectral Scanner

Landsat-3 carries the first Multispectral Scanner (MSS) to include sensing of a fifth spectral band for the thermal emission of the earth scene in addition to the first four bands, which sense reflected solar irradiance. Unique design features of this band are described: a thermal reference level provided by the detector viewing its cold surroundings in a mirror, and an incremental gain adjustment used to maintain dynamic range without penalizing the signal-to-noise ratio. Ground calibration of the thermal band was performed using a large-area blackbody source. During that testing the detector and instrument temperatures were varied. The body of data thus generated was analyzed using calibration algorithms which were derived by a weighted least-squares technique. The resulting values were then applied to the remainder of the thermal vacuum test data as verification of the adequacy of the calibration. The data obtained from space would be used to identify the appropriate function to find signal radiance from scanner signal in a manner shown.