The ASTER On-Demand L2 Surface Radiance TIR is an on-demand product generated using the five thermal infra-red (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 90 meters spatial resolution, which includes both surface-emitted and surface-reflected components. It also provides the down-welling ... 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 2 elements: 1) It uses a radiative transfer model which is capable of estimating the magnitude of atmospheric emission, absorption, and scattering. It uses Modtran (Moderate Resolution Transmittance Code) radiative transfer model, which calculates atmospheric transmittance and radiance for frequencies from 0 to 50,000 cm-1 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.
V002 data set release date: 2001-03-28
V003 data set release date: 2002-05-03
The key determinants between these versions are the use of a newer algorithm with an improved set of radiometric calibration and geometric correction coefficients databases in version 003.
Data Set Characteristics:
Area: ~60 km x 60 km
Image Dimensions: 700 rows x 830 columns
File Size: ~14 Megabytes
Units: w/m2/sr/µm surface radiance, w/m2/µm sky irradiance
Projection: Universal Transverse Mercator (UTM)
Data Format: HDF-EOS or GeoTIFF
Vgroup Data Fields: 5 surface radiance, 5 sky irradiance