EMIT L1B At-Sensor Calibrated Radiance and Geolocation Data 60 m

PI: Robert Green

The Algorithm Theoretical Basis Document (ATBD) is being updated and a new version will be posted as soon as reviews are complete.


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 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 1B At-Sensor Calibrated Radiance and Geolocation (EMITL1BRAD) Version 1 data product provides at-sensor calibrated radiance values along with observation data in a spatially raw, non-orthocorrected format. Each EMITL1BRAD granule consists of two Network Common Data Format 4 (NetCDF4) files at a spatial resolution of 60 meters (m): Radiance (EMIT_L1B_RAD) and Observation (EMIT_L1B_OBS). The Radiance file contains the at-sensor radiance measurements of 285 bands with a spectral range of 381-2493 nanometers (nm) and with a spectral resolution of ~7.5 nm, which are held within a single science dataset layer (SDS). The Observation file contains viewing and solar geometries, timing, topographic, and other information related to the observation.

Each NetCDF4 file holds a location group containing geometric lookup tables (GLT), which are orthorectified images that provide relative x and y reference locations from the raw scene to allow for projection of the data. Along with the GLT layers, the files also contain latitude, longitude, and elevation layers. The latitude and longitude coordinates are presented using the World Geodetic System (WGS84) ellipsoid. The elevation data was obtained from Shuttle Radar Topography Mission v3 (SRTM v3) data and resampled to EMIT’s spatial resolution.

Each granule is approximately 75 kilometer (km) by 75 km, nominal at the equator, and some granules near the end of an orbit segment reaching 150 km in length.

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Collection and Granule


Characteristic Description
File Size~1.8 GB
Temporal ResolutionVaries
Temporal Extent2022-08-09 to Present
Spatial ExtentGlobal (52 °N to 52 °S Latitude)
Coordinate SystemGeographic Latitude and Longitude
DatumWorld Geodetic System (WGS84)
File FormatnetCDF-4
Geographic Dimensions74.5 km x 76.8 km


Characteristic Description
Number of Science Dataset (SDS) Layers10
Columns/Rows1242 x 1280
Pixel Size60 m

Layers / Variables

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
radiance1 Radiance Data, (12804x1242x285) μW/cm²/sr/nm 32-bit floating point -9999.00 N/A N/A N/A
obs2 3D array with band parameters specified, (12804x1242x11) N/A 32-bit floating point -9999.00 N/A N/A N/A
glt_x3 Geometric lookup table – x values N/A 32-bit signed integer -9999 0 1 to 1242 N/A
glt_y3 Geometric lookup table – y values N/A 32-bit signed integer -9999 0 1 to 2559 N/A
lat3 Latitude Degree 64-bit floating point -9999.0000 N/A -90 to 90 N/A
lon3 Longitude Degree 64-bit floating point -9999.0000 N/A -180 to 180 N/A
elev3 Elevation Meters 64-bit floating point -9999.0000 N/A N/A N/A
wavelengths1 Wavelength centers Nanometers 32-bit floating point -9999.00 N/A N/A N/A
fwhm1 Full width at half maximum Nanometers 32-bit floating point -9999.00 N/A N/A N/A
observation_bands2 Array of strings indicating the name of each observation band N/A N/A N/A N/A N/A N/A

4 Scenes have at least 1280 rows. To prevent small scenes, scenes at the end of an orbit segment will have up to 2559 rows.

Observation SDS Bands

Band Name Units Comments
Path length meters Distance between sensor and ground
To-sensor azimuth Degree 0 to 360 degrees clockwise from N
To-sensor zenith Degree 0 to 90 degrees from zenith
To-sun azimuth Degree 0 to 360 degrees clockwise from N
To-sun zenith Degree 0 to 90 degrees from zenith
Solar phase Degree Degrees between to-sensor and to-sun vectors in principal plane
Slope Degree Local surface slope as derived from Digital Elevation Model (DEM) in degrees
Aspect Degree Local surface aspect 0 to 360 degrees clockwise from N
Cosine(i) N/A Apparent local illumination factor based on DEM slope and aspect and to sun vector, 0 to 1
UTC Time Hours Fractional hours since UTC midnight
Earth-sun distance (AU) Astronomical Units Distance between the Earth and the Sun.

** All geometry products in the observation dataset are calculated using SRTM as a surface.

Product Quality

Quality information for the EMITL1BRAD Version 1 data product is not provided.

Known Issues

  • Data acquisition gap: From September 13, 2022, through January 6, 2023, a power issue outside of EMIT caused a pause in operations. Due to this shut down, no data were acquired during that timeframe.

About the image

An At-Sensor Calibrated Radiance RGB image (bands 36, 22, 10) and data cube showcasing spectral signatures of the data from the EMITL1BRAD product over Libya, Africa on August 17, 2022.

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User Guide
Algorithm Theoretical Basis Document (ATBD)

Using the Data

Access Data


DOI: 10.5067/EMIT/EMITL1BRAD.001