This organization will contain the algorithms for the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission collection 3 data products.

Please refer to the ECOSTRESS tutorials for information on accessing and utilizing the ECOSTRESS data products.

ECOSTRESS collection 3 is the precursor to the Surface Biology and Geology Thermal Infrared (SBG-TIR) Orbiting Terrestrial Thermal Emission Radiometer (OTTER) data products.

This document will provide background information relevant to the ECOSTRESS mission and data products.

The ECOSTRESS data product algorithms include:

• Level 1 Radiance
• Level 2 Surface Temperature
• Level 2 Vegetation Index & Albedo
• Level 3 Evapotranspiration
  • Level 4 Evaporative Stress Index
  • Level 4 Water Use Efficiency

The evapotranspiration models for the level 3 and 4 ecosystem products are being developed in the JPL-Evapotranspiration-Algorithms organization. These models include:

• Surface Temperature Initiated Closure (STIC)
• Breathing Earth System Simulator (BESS)
• Priestley Taylor Jet Propulsion Laboratory (PT-JPL)
• Priestley Taylor Jet Propulsion Laboratory Soil Moisture (PT-JPL-SM)

The STARS data fusion system supporting the auxiliary inputs for the ecosystem products is being developed in the STARS-Data-Fusion organization.

The Julia implementation for the STARS data fusion algorithm is in STARS.jl.

There are several supporting sub-components in generalized Julia packages, including:

• SentinelTiles.jl for geo-referencing Sentinel UTM tiles
• MODLAND.jl for geo-referencing MODIS/VIIRS sinusoidal tiles
• CMR.jl for searching the Common Metadata Repository (CMR)
• HLS.jl for searching and downloading the Harmonized Landsat Sentinel (HLS) dataset
• VNP43NRT.jl for Bidirectional Reflectance Distribution Function (BRDF)

All ECOSTRESS tiled products are stored in the Geographic Tagged Image File Format (GeoTIFF). GeoTIFF is a general purpose file format and programming library for storing scientific data. The GeoTIFF format was originally created by Dr. Niles Ritter with the Open Geospatial Consortium publishing the OGC GeoTIFF standard, which defines the GeoTIFF by specifying requirements and encoding rules for using the Tagged Image File Format (TIFF) for the exchange of georeferenced or geocoded image data. The following sections provide some key elements of GeoTIFF that will be employed in ECOSTRESS data products.

The tiled products include the letter T in their level identifiers: L1CT, L2T, L3T, and L4T. The tiling system used for ECOSTRESS is borrowed from the modified Military Grid Reference System (MGRS) tiling scheme used by Sentinel 2. These tiles divide the Universal Transverse Mercator (UTM) zones into square tiles 109800 m across. SBG uses a 60 m cell size with 1830 rows by 1830 columns in each tile, totaling 3.35 million pixels per tile. This allows the end user to assume that each 60 m SBG pixel will remain in the same location at each timestep observed in analysis. The COG format also facilitates end-user analysis as a universally recognized and supported format, compatible with open-source software, including QGIS, ArcGIS, GDAL, the Raster package in R, rioxarray in Python,and Rasters.jl in Julia.

Each float32 data layer occupies 4 bytes of storage per pixel, which amounts to an uncompressed size of 13.4 mb for each tiled data layer. The uint8 quality flag layers occupy a single byte per pixel, which amounts to an uncompressed size of 3.35 mb per tiled data quality layer.

Each .tif COG data layer in each L2T/L3T/L4T product additionally contains a rendered browse image in GeoJPEG format with a .jpeg extension. This image format is universally recognized and supported, and these files are compatible with Google Earth. Each L2T/L3T/L4T tile granule includes a .json file containing the Product Metadata and Standard Metadata in JSON format.

Each ECOSTRESS tiled product in COG format will contain a standard metadata group that specifies the same type of contents for all products, and a product specific metadata group that specifies those metadata elements that are useful for defining attributes of the product data.

Complete documentation of the GeoTIFF structure and application software can be found at https://www.ogc.org/standard/geotiff/.

Two high-level quality flags are provided in all gridded and tiled products as thematic/binary masks encoded to zero and one in unsigned 8-bit integer layers. The cloud layer represents the final cloud test from L2 CLOUD. The water layer represents the surface water body in the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model. For both layers, zero means absence, and one means presence. Pixels with the value 1 in the cloud layer represent detection of cloud in that pixel. Pixels with the value 1 in the water layer represent open water surface in that pixel. All tiled product data layers written in float32 contain a standard not-a-number (NaN) value at each pixel that could not be retrieved. The cloud and water layers are provided to explain these missing values.

Table 3. Standard metadata included in SBG-TIR product files

Table 4. Abbreviations and acronyms used in SBG-TIR documentation and products