Terra ASTER surface radiance TIR band 10 data from the AST_09T product over Canada on August 2, 2018.
View full-size imageThe Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Surface Radiance TIR (AST_09T) is generated using the five Thermal Infrared (TIR) bands (acquired either during the day or night time) between 8 and 12 µm spectral range. It provides surface-leaving radiance for the TIR bands at a spatial resolution of 90 meters, which includes both surface-emitted and surface-reflected components. It also provides the downwelling sky irradiance values (in W/m2/µm) for each of the TIR bands. This product is atmospherically corrected, and the surface-leaving radiance is of known accuracy and valid only for clear-sky scenes (cloud-free pixels). This atmospherically corrected product provides the input for generating two other higher-level products: surface spectral emissivity and surface kinetic temperature.
The algorithm to correct atmospheric effects involves two elements: 1) it uses a radiative transfer model which is capable of estimating the magnitude of atmospheric emission, absorption, and scattering. It uses the Moderate Resolution Transmittance Code (MODTRAN) radiative transfer model, which calculates atmospheric transmittance and radiance for frequencies from 0 to 50,000 cmˉ¹ at moderate spectral resolution. 2) It identifies and incorporates all the necessary atmospheric parameters applicable to the location and time for which the measurements require correction. These include temperature, water vapor, elevation, ozone, and aerosols.
The ASTER L2 Surface Radiance TIR data product is only available through NASA’s Earthdata Search. The ASTER Order Instructions provide step-by-step directions for ordering this product.
The Science Scalable Scripts-based Science Processor for Missions (S4PM) Version 3.4 algorithm, which is used to generate L2 Product Generation Executables (PGEs), is relying on a new ancillary input for atmospheric parameters. Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) is global atmospheric reanalysis that combines remote sensing observations and interactions with the climate system. It will be one of the primary ozone and water vapor, pressure, and temperature inputs for L2 PGEs. MERRA-2 will provide a finer geographic resolution grid since it is a 3-dimensional, 3-hourly data collection with 50-km (latitudinal direction) spatial resolution.
The fallback options for L2 PGEs are as follows:
Ozone: [TOVS Ozone (OZ_DLY ) > AURA Ozone Monitoring Instrument (AURAOMI) > Total Ozone Analysis from Stratospheric and Tropospheric (TOAST) > Earth Probe-Total Ozone Mapping Spectrometer (EPTOMS)] or [MERRA-2] > National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS) > Climatology
Water Vapor, Pressure, and Temperature: [MOD07_L2] or [MERRA-2] > NCEP/GDAS > Climatology
Caveat: The temporal range for MERRA-2 covers 1980 to present; however, there is latency of ~3 weeks after the end of a month. Hence, NCEP/GDAS > Climatology fallback sequence will be applied for on-demand requests that fall outside of MERRA-2’s temporal range or if the data is not science grade.
Starting June 23, 2021, radiometric calibration coefficient Version 5 (RCC V5) will be applied to newly observed ASTER data and archived ASTER data products. Details regarding RCC V5 are described in the following journal article.
Tsuchida, S., Yamamoto, H., Kouyama, T., Obata, K., Sakuma, F., Tachikawa, T., Kamei, A., Arai, K., Czapla-Myers, J.S., Biggar, S.F., and Thome, K.J., 2020, Radiometric Degradation Curves for the ASTER VNIR Processing Using Vicarious and Lunar Calibrations: Remote Sensing, v. 12, no. 3, at https://doi.org/10.3390/rs12030427.
As of December 15, 2021, the LP DAAC has implemented changes to ASTER PGE Version 3.4, which will affect all ASTER Level 2 on-demand products. Changes include:
Additionally, Climatology, which is one of the inputs for Ozone and Moisture, Temperature and Pressures (MTP) will be removed from the Earthdata Order Form. It has been observed that PGEs generated with Climatology as an input yield noticeable differences statistically during image and spectral analysis. Climatology will continue to be used as the final default if neither of the first two selectable options are available for Ozone and MTP. Users can check the OPERATIONALQUALITYFLAGEXPLANATION field in the metadata or the output file for atmospheric parameters that were applied.
| Characteristic | Description |
|---|---|
| Collection | Terra ASTER |
| DOI | 10.5067/ASTER/AST_09T.003 |
| File Size | ~14 MB |
| Temporal Resolution | Varies |
| Temporal Extent | 2000-03-04 to Present |
| Spatial Extent | Global |
| Coordinate System | Universal Transverse Mercator (UTM) |
| Datum | World Geodetic System (WGS84) |
| File Format | HDF-EOS or GeoTIFF |
| Geographic Dimensions | ~60 km x 60 km |
| Characteristic | Description |
|---|---|
| Number of Science Dataset (SDS) Layers | 5 |
| Columns/Rows | 700 x 830 |
| Pixel Size | 90 m |
| SDS Name | Description | Units | Data Type | Fill Value | No Data Value | Valid Range | Scale Factor |
|---|---|---|---|---|---|---|---|
| TIR_Band10 | 90 meter resolution TIR Band 10 (8.125 to 8.475 µm) | W/m²/sr/μm | 16-bit signed integer | N/A | N/A | 0 to 3000 | 0.006882 |
| TIR_Band11 | 90 meter resolution TIR Band 11 (8.475 to 8.825 µm) | W/m²/sr/μm | 16-bit signed integer | N/A | N/A | 0 to 3000 | 0.006780 |
| TIR_Band12 | 90 meter resolution TIR Band 12 (8.925 to 9.275 µm) | W/m²/sr/μm | 16-bit signed integer | N/A | N/A | 0 to 3000 | 0.006590 |
| TIR_Band13 | 90 meter resolution TIR Band 13 (10.25 to 10.95 µm) | W/m²/sr/μm | 16-bit signed integer | N/A | N/A | 0 to 3000 | 0.005693 |
| TIR_Band14 | 90 meter resolution TIR Band 14 (10.95 to 11.65 µm) | W/m²/sr/μm | 16-bit signed integer | N/A | N/A | 0 to 3000 | 0.005225 |
The Science Scalable Scripts-based Science Processor for Missions (S4PM) Version 3.4 algorithm, which is used to generate L2 Product Generation Executables (PGEs), is relying on a new ancillary input for atmospheric parameters. Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) is global atmospheric reanalysis that combines remote sensing observations and interactions with the climate system. It will be one of the primary ozone and water vapor, pressure, and temperature inputs for L2 PGEs. MERRA-2 will provide a finer geographic resolution grid since it is a 3-dimensional, 3-hourly data collection with 50-km (latitudinal direction) spatial resolution.
The fallback options for L2 PGEs are as follows:
Ozone: [TOVS Ozone (OZ_DLY ) > AURA Ozone Monitoring Instrument (AURAOMI) > Total Ozone Analysis from Stratospheric and Tropospheric (TOAST) > Earth Probe-Total Ozone Mapping Spectrometer (EPTOMS)] or [MERRA-2] > National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS) > Climatology
Water Vapor, Pressure, and Temperature: [MOD07_L2] or [MERRA-2] > NCEP/GDAS > Climatology
Caveat: The temporal range for MERRA-2 covers 1980 to present; however, there is latency of ~3 weeks after the end of a month. Hence, NCEP/GDAS > Climatology fallback sequence will be applied for on-demand requests that fall outside of MERRA-2’s temporal range or if the data is not science grade.