Validation and quality assessment of the ECOSTRESS level-2 land surface temperature and emissivity product

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) was launched to the International Space Station (ISS) on June 29, 2018, and currently provides the highest spatial resolution thermal infrared (TIR) data (38m × 69m) available from space. In this study, we validated the ECOSTRESS level-2 Land Surface Temperature and Emissivity (LST&E) product at fourteen sites located in North America, Europe, and Africa to the Committee on Earth Observation Satellites (CEOS) Land Product Validation (LPV) Stage-1 status. Two primary methods are recommended for the validation of LST data: a Temperature-based (T-based) and a Radiance-based (R-based) method. The T-based method requires calibrated measurements of the ground leaving radiance concurrent with the satellite overpass. In contrast, the R-based method uses a radiative closure simulation with external atmospheric profiles and an a priori knowledge of surface emissivity. Using these methods, we validated 1,139 ECOSTRESS clear-sky observations between August 1, 2018, and March 31, 2020. In general, there was good agreement with ground-based measurements with an average root mean square error (RMSE) of 1.07 K in LST and r² values ranging from 0.988-0.997 for all sites. A cold bias of ~0.75 K was identified for temperatures below 295 K linked to calibration issues that will be addressed in future reprocessing of the data. Retrieved emissivity comparisons with laboratory spectra had an RMSE of 0.023 (2.3%) for all bands on average. With the decommissioning of ASTER on Terra in 2023, the multispectral and high spatial resolution characteristics of ECOSTRESS data serves as a bridge to NASA’s Surface Biology and Geology (SBG) designated observable. SBG will launch as early as 2026 and will join other international TIR missions such as the Thermal infraRed Imaging Satellite for High-resolution Natural resource Assessment (TRISHNA) and the Land Surface Temperature Monitoring (LSTM) mission, which have launch dates of 2025 and 2028, respectively.