NASA Land Surface Temperature and Emissivity (PDF link)
The MOD21 product was developed at JPL and is produced by the ASTER Temperature Emissivity Separation (TES) algorithm that was adapted to work with MODIS bands 29, 31 and 32. The MOD21 product addresses the problem of algorithm inconsistency between sensors, which makes intercomparisons difficult to interpret, introduces uncertainties when resampling data, and limits their usefulness in models and as Earth system data records which require consistent and accurate emissivities over all land cover types at a range of spatial, spectral and temporal scales.
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