High-resolution temperature and emissivity mapping (HiTeSEM): A satellite sensor concept for hyperspectral thermal remote sensing

Abstract

HiTeSEM (High-resolution Temperature and Spectral Emissivity Mapping) is a preparatory study, funded by the German Aerospace Center (DLR) that aims at preparing the floor for a future spaceborne hyperspectral thermal mission. Up to now this spectral region in Earth observation is mainly used to measure surface temperature. Nevertheless, the spectrally dispersed signal between 8μm and 12 μm can provide information about abundances of key rock and soil forming minerals as well as the status of vegetation. HiTeSEM aims at closing the research gap still hampering utilization of the thermal infrared data at reasonable spectral and spatial resolution and focusses on surface-solid Earth interactions to assess natural and human-induced changes. Land surface temperature (LST) and spectral emissivity (LSE) of the Earth are the basis for the extraction of sensitive variables in geology, pedology, vegetation monitoring, and biosphere-pedosphere interaction. Towards this end, HiTeSEM will enable the research community to evaluate the potential of emissive spectroscopy methodologies in Earth observation to answer a series of key science questions related to global change, human health, and food security. Relevant target variables include soil mineral composition, soil organic matter (SOM), surface moisture availability, evapotranspiration and stomatal/surface conductance. These are key indicators for soil productivity and plant stress in sensitive regions and can be used to govern and adapt land use practices under challenging ecological and climatic conditions. In urban remote sensing HiTeSEM is expected to furnish important information to define thermal models, which implies knowledge of the surface material composition by means of spectral emissivity retrieval. The methodological challenge of HiTeSEM lies in the development of a robust high performance temperature emissivity separation (TES) technique to allow optimum pre-processing of the measured thermal radiance signal at the sensor level. The above science goals define the technical baseline for the proposed mission, namely a system composed of a thermal infrared spectrometer covering the spectral region of 8 – 12.5 µm with ~75 spectral channels, a swath width of 50 km - 100 km, and a ground IFOV of 60 x 60 m2 (TIR, hyperspectral) and 20 x20 m2 (TIR, broadband). The retrieval of emissivity spectra requires low noise equivalent temperatures, in the order of 0.05 K @ 300 K