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 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 2 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) and uncertainty is calculated within each 0.5 degree grid cell in the EMITL3ASA product for each of the EMIT-10 minerals. Grainsize was determined to be the strongest contributor to abundance variation, and as such layers calculated using the 2.5 and 97.5 percentile confidence interval of the grainsize are provided for use in uncertainty quantification.

The EMITL3ASA data product contains 30 Science Dataset (SDS) layers. There are three layers for each of the EMIT-10 minerals: one layer containing mineral spectral abundance and two layers for uncertainty quantification containing mineral spectral abundance at 2.5 and 97.5 percentile confidence intervals of grainsize. The latitude and longitude layers contain the coordinates for the upper left corner of each pixel.

Known Issues

• Minor Abundance Estimate Discrepancy. A transcription error in the grain-size median prediction caused a minor discrepancy in the EMITL3ASA Version 2 mineral spectral abundance estimates. The issue caused deviations well within the uncertainty estimates, typically far below 1%. The most affected estimate is calcite, with maximum deviations reaching 2% for a very small number of pixels. Iron oxides are virtually unaffected.

Improvements/Changes from Previous Versions

• Version 2 data produced using a fundamentally new model to obtain spectral abundance from L2BMIN data.
• Added grainsize dependency into the new model.