Temperature / Emissivity Separation Algorithm Theoretical Basis Document
نویسندگان
چکیده
The ASTER scanner on NASA's Terra (EOS-AM1) satellite will collect five channels of TIR data with an NE∆T of ≤0.3K to estimate surface kinetic temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER's TES algorithm hybridizes two established algorithms, first estimating the temperature and band emissivities by the Normalized Emissivity Method, and then normalizing the emissivities by their average value. Next, an empirical relationship adapted from the Alpha Residual method is used to predict the minimum emissivity from the spectral contrast (min-max difference or MMD) of the normalized values, permitting recovery of the emissivity spectrum with improved accuracy. TES uses an iterative approach to remove reflected sky irradiance. Input to TES consists of land-leaving radiances (compensated for atmospheric absorption and path radiance) and downwelling sky irradiance. Based on numerical simulation, TES can recover temperatures within about ±1.5 K, and emissivities within about ±0.015. Limitations arise from the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTER's precision, calibration, and atmospheric correction.
منابع مشابه
HyspIRI Level-2 Thermal Infrared (TIR) Land Surface Temperature and Emissivity Algorithm Theoretical Basis Document
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