Landsat Collection 2 Surface Temperature products are generated from several input data sources and atmospheric profiles. This includes NASA's Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Emissivity Dataset (GED).
The ASTER GED dataset is created from all clear-sky pixels of ASTER scenes acquired from 2000 through 2008. While this dataset has a global spatial extent, there are areas that are missing the mean emissivity information due to persistent cloud contamination in the ASTER measurements. When mean emissivity information is missing, the Surface Temperature product will contain areas of missing data.