Advancing the geosciences with thermal infrared orbital data: Future possibilities or a looming data gap?

The use of high spatial resolution orbital thermal infrared (TIR) data for certain geoscience applications has been possible for the past four decades. Satellites having one or two TIR spectral bands were able to detect the spatial patterns and temporal baselines of surface temperature; however, they do not provide any information on emissivity variation (essential for mapping critical minerals), and less accurate temperatures than multispectral TIR systems. In 2000, ASTER (the first multispectral TIR sensor with sub 100 m spatial resolution) was launched and has acquired data for over 25 years but will be decommissioned in 2026. A similar instrument (ECOSTRESS) was launched to the International Space Station (ISS) in 2018 and is still functioning, but it will be retired in 2030 with the ISS leaving a gap in US multispectral TIR capability. Multispectral TIR data expanded what was possible in the geosciences, providing compositional information such as surface mineralogy, thermal inertia, and particulate mapping, together with more accurate and refined uses of surface temperatures. Several countries/space agencies are planning high spatial, high temporal resolution multispectral TIR missions in the near future that will provide continuity and greatly expand possible applications with much higher repeat times. One of these, the Surface Biology and Geology (SBG-TIR) mission would provide MIR (3–5 μm) and TIR (8–12 μm) image data at ~ 60 m spatial resolution every 1-3 days. SBG-TIR is a joint-endeavor between NASA and ASI in Italy with planned geoscience data products such as surface mineralogy and volcanic activity, whereas the other planned missions do not have this geological focus. The TIR spectral resolution was increased to six bands for SBG-TIR, which vastly improves the capability of discriminating feldspar and clay mineralogy mapping as well as aerosol detection in sulfur dioxide rich plumes. The global mapping of the major rock-forming minerals and their weight percent silica together with the detection of subtle thermal and compositional changes at volcanoes will be possible for the first time with SBG-TIR. As part of the mission development, our work examined prior ASTER and airborne MASTER TIR data to test both the mineral mapping and precursory thermal volcanic eruption signal detection possible with SBG-TIR. ASTER provides the long time series to quantify low-level anomalies and small eruption plumes over long periods, whereas the airborne MASTER provides the spectral resolution necessary to identify minerals. The findings of the surface mineralogy and volcanic activity algorithm development will be presented and compared to those from the other planned TIR missions with lower spectral resolutions. Critically however, the SBG-TIR mission’s future is now uncertain due to recent budgetary reductions by the United States federal government. While the other European multispectral TIR mission move ahead, NASA is in danger of permanently losing its advantage in this technology space. This looming high resolution, multispectral TIR gap will reduce science outcomes and render others such as mineral mapping impossible.