AST_09T v003

ASTER Surface Radiance TIR


PI: U.S./Japan ASTER Science Team

Description

The 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.

Characteristics

Collection and Granule

Collection

Characteristic Description
CollectionTerra ASTER
DOI10.5067/ASTER/AST_09T.003
File Size~14 MB
Temporal ResolutionOther
Temporal Extent2000-03-04 to Present
Spatial ExtentGlobal
Coordinate SystemUniversal Transverse Mercator (UTM)
DatumWorld Geodetic System (WGS84)
File FormatHDF-EOS or GeoTIFF
Geographic Dimensions~60 km x 60 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers5
Columns/Rows700 x 830
Pixel Size90 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Additional Offset
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 N/A
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 N/A
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 N/A
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 N/A
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 N/A

There are 3 groups of ancillary data inputs used in the atmospheric correction of ASTER radiance and reflectance:

  1. Ozone data input: The NCEP/TOVS (National Centers for Environmental Prediction/TIROS (Television & Infrared Observation Satellite) Operational Vertical Sounder) data are acquired from a NOAA satellite, and provides the ancillary column ozone data twice daily. This was the default option with the alternative Naval Research Laboratory's (NRL) Ozone Climatology dataset. Starting on April 18, 2005, NOAAs TOVS developed an irreversible instrument problem, and therefore, the use of the NCEP/TOVS ancillary data was discontinued for ASTER Level-1 data acquired from April 18, 2005 onward. This ancillary data source is available for ASTER data acquired prior to April 18, 2005. Currently, the only alternative in use for column ozone is NRLs Ozone Climatology dataset.
  2. Aerosol data input: Presently, NRLs Aerosol Climatology ancillary data are the only available input.
  3. Temperature, Atmospheric pressure, and Moisture Profile data inputs: The source of these data are the NCEP-GDAS (Global Data Assimilation System) available at every 6 hours temporal frequency. The alternative is the NRL Climatology dataset. These datasets are based on modeling, simulation, and prediction, and therefore, they are static, monthly, averaged datasets used only as a last resort.

Documentation

Using the Data

E-Learning

View from NASA Terra's Zoom Lens: All About the ASTER Sensor

Tools

Citation

DOI: 10.5067/ASTER/AST_09T.003

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