The Earth Surface Mineral Dust Source Investigation (EMIT) instrument measures surface mineralogy, targeting the Earth’s arid dust source regions. The measurements will then be used as input data for the composition of dust sources in Earth System Models (ESM). EMIT is installed on the International Space Station (ISS) and uses imaging spectroscopy to take mineralogical measurements of sunlit regions of interest between 52° N latitude and 52° S latitude. Up to five visits (three on average) of each arid target region are scheduled, only downlinking acquisitions that are not dominated by cloud cover. The EMIT instrument is an imaging spectrometer that uses contiguous spectroscopic measurements in the visible to shortwave infrared region of the spectrum to resolve absorption features of dust-forming minerals. EMIT has a viewing swath width of 75 km, measuring 285 bands at a spatial resolution of 60 m. Maps of the relative abundance of source minerals that are generated from EMIT data will advance our understanding of the current and future impacts of mineral dust in the Earth system. Learn more on the EMIT website.
EMIT filenames (i.e., the local granule ID) follow a naming convention which gives useful information regarding the specific product.
Level 1 and 2 data product filenames will adhere to the following naming convention: EMIT_L1B_RAD_001_20220101T083015_2200105_007
Level 2B Estimated Methane Plume Complexes cloud optimized GeoTIFF filenames adhere to the following naming convention: EMIT_L2B_CH4PLM_001_20220101T083015_000120
For level 3 and 4 data products, filenames will follow the naming convention: EMIT_L3_ASA_001
Each EMIT product may contain multiple NetCDF files and one quick look PNG file. The PNG file name will match the main product of the collection but will have PNG as the data format. For example, the EMITL1BRAD data product contains two separate NetCDF files: radiance (EMIT_L1B_RAD_001_20220101T083015_2200105_007.nc) and observation (EMIT_L1B_OBS_001_20220101T083015_2200105_007.nc). The browse file will be EMIT_L1B_RAD_001_20220101T083015_2200105_007.png.
The EMIT Product Long Name (i.e., Collection-Level) naming convention provides useful information regarding all EMIT swath products.
Below is an example for an EMIT Level 1B product, although all EMIT Product Long Names follow the same structure.
The EMIT L1B At-Sensor Calibrated Radiance and Geolocation Data 60 m V001 collection has the following characteristics:
All EMIT products distributed from the LP DAAC are produced at nominally daily temporal resolution. The true revisit period for a given location is variable based on the instrument’s orbital cycle aboard the ISS.
L1 and L2 EMIT products are produced at 60 m spatial resolution.
L3 EMIT products are produced at 0.5° x 0.5° resolution.
L4 EMIT products are produced using a 2° latitude by 2.5° longitude horizontal model grid.
EMIT data products contain location information in spatially raw format (non-orthocorrected). The location data provided are latitude, longitude, and elevation. The latitude and longitude coordinates are given in ESPG:4326 (World Geodetic System-84) and the longitude values are Easting (increasing eastward from Greenwich). The elevation dataset is estimated at pixel center and sourced from the Shuttle Radar Topography Mission (SRTM v3), which is then resampled to EMIT’s native 60 m spatial resolution.
EMIT data products will follow NASA's Earth Observing System Data and Information System (EOSDIS) data processing levels.
The LP DAAC distributes EMIT data processed to Level-1 or higher:
The EMIT mission generates five distributable data products that represent four levels of data processing. EMIT starts and stops data recording based on a surface coverage mask. This period of data recording within an orbit is referred to as a scene and can cover thousands of kilometers down-track. The area covered depends on the acquisition mask map. For the sake of convenience, each scene is broken into granules of 1280 down-track lines which can be reassembled seamlessly into scenes. The last granule can be extended up to 2559 lines to prevent having a granule with very few lines. As a scene is collected, the raw data are stored on a high-speed Solid-State Data Recorder (SSDR). From there the avionics software reads the uncompressed data, packages it into frames of 32 instrument lines, screens the frames for cloudy pixels, and then performs a lossless 4:1 compression of the processed science data before storing it back onto the SSDR. The data is then downlinked to the EMIT Instrument Operation System (IOS) and delivered to the Science Data System (SDS) where Level 0 processing occurs. The Level 0 data is then further processed into Level 1B, Level 2A, Level 2B, and Level 3 data. Level 4 data products will be generated late in the EMIT mission lifecycle.
|Spectral Range||381 to 2493 nanometers (nm)|
|Number of Bands||285|
|Spectral Resolution||~7.5 nm|
EMIT products have two sources of metadata: embedded NetCDF metadata and the external ECS (generated by the EOSDIS Core System) metadata. The NetCDF metadata contains valuable information including global attributes and dataset specific attributes pertaining to the granule. The ECS .met file is the external metadata file in XML format, which is delivered along with the EMIT product and contains a subset of the NetCDF metadata. The metadata details for each product are provided within their respective user guide located on the DOI landing page.
Data can be discovered and accessed through NASA Earthdata Search.
All EMIT standard products are stored in the Network Common Data Form version 4 (NetCDF4), excluding the quick browse image, which is in PNG format. NetCDF4 is a community standard for sharing scientific data.
Certain freely available and proprietary software are available for use with EMIT NetCDF4 products:
Freely Available Software