The Earth Surface Mineral Dust Source Investigation (EMIT) instrument measures surface mineralogy, targeting the Earth’s arid dust source regions. EMIT is installed on the International Space Station (ISS) and uses imaging spectroscopy to take mineralogical measurements of the sunlit regions of interest between 52° N latitude and 52° S latitude. An interactive map showing the regions being investigated, current and forecasted data coverage, and additional data resources can be found on the VSWIR Imaging Spectroscopy Interface for Open Science (VISIONS) EMIT Open Data Portal.

The EMIT Level 3 Aggregated Mineral Spectral Abundance and Uncertainty (EMITL3ASA) Version 1 data product provides an aggregated mineral spectral abundance of the 10 minerals that are the focus of the EMIT mission. These minerals, referred to as the EMIT-10 minerals, are calcite, chlorite, dolomite, goethite, gypsum, hematite, illite+muscovite, kaolinite, montmorillonite, and vermiculite. The EMITL3ASA granule consists of one network Common Data Format 4 (netCDF-4) file at a spatial resolution of 0.5 degrees. The data in EMITL3ASA relies heavily on the EMIT L2B Estimated Mineral Identification and Band Depth and Uncertainty (EMITL2BMIN) data. Using the EMITL2BMIN data, aggregated spectral abundance (ASA) is calculated for each of the EMIT-10 minerals as the simple average of relevant 60 m pixels within each 0.5 degree grid cell in the EMITL3ASA product, after controlling for the estimated fractional cover of bare soil within the pixel.

The EMITL3ASA data product contains 22 Science Dataset (SDS) layers. There are two layers for each of the EMIT-10 minerals: mineral spectral abundance and mineral spectral abundance uncertainty. The latitude and longitude layers contain the coordinates for the upper left corner of each pixel.

Known Issues

• The current version of the spectral unmixing algorithm may retrieve spuriously high non-photosynthetic vegetation values over bare playas. Algorithmic fixes are underway and will be integrated during the first data reprocessing cycle. As such, some bare playas are excluded from the current L3 aggregation.
• Spectral abundance is a measure of optical abundance, not of mass fraction. Conversion to mass or volume fraction requires leverage on particle grain size, which is not incorporated into the current model. Given this limitation, this product should not be used directly as a measure of mass fraction.