Quantification of CH4 Emissions from the EMIT and AVIRIS-3 Imaging Spectrometers

Spaceborne and airborne imaging spectrometers can identify methane (CH₄) plumes and enable emission quantification and direct sectoral attribution necessary to better constrain methane emissions and inform mitigation strategies. We will show CH₄ emission quantification results and accompanying uncertainty products for CH₄ plume observations from NASA’s Earth surface Mineral dust source InvesTigation (EMIT) imaging spectrometer onboard the International Space Station, as well as the recently developed Airborne Visible/Infrared Imaging Spectrometer 3 (AVIRIS-3). The differing spatial resolution and instrument sensitivity of the EMIT and AVIRIS-3 sensors are highly complementary for tiered CH₄ plume detection and quantification. The large spatial coverage from EMIT allows us to identify and quantify previously unknown emissions from CH₄ point sources across large regions of the Earth’s surface, while AVIRIS-3 has higher sensitivity and increased spatial resolution for characterizing CH₄ emissions below EMIT’s detection limit.

Building on a legacy of greenhouse gas retrievals first developed for airborne imaging spectrometers (e.g., AVIRIS, AVIRIS-NG), we use a matched filter approach to retrieve CH₄ enhancements and the per-plume integrated mass enhancement (IME) method with windspeed data to estimate hourly CH₄ emission rates. We take a two-pronged approach to validating our CH₄ emission detection and quantification method: (1) an AVIRIS-3 CH₄ controlled release experiment with multiple flow rates, and (2) evaluation of a simultaneous collection of AVIRIS-3 and EMIT in West Texas’ Permian Basin oil-and-gas producing region. This validation work will help provide confidence in EMIT’s plume quantification approach, which is important as imaging spectrometers are necessary for more comprehensive understanding of global CH₄ point source emissions and greenhouse gas budgets, particularly in areas with limited reporting requirements. Lastly, the EMIT greenhouse gas portal (https://earth.jpl.nasa.gov/emit/data/data-portal/Greenhouse-Gases/) is actively distributing methane data products in support of NASA’s Open Source Science Initiative and AVIRIS-3 data will soon be publicly available for interested decision-makers and users (e.g., U.S. Greenhouse Gas Center).