I think you must mean that your ASTER data are in HDF (not HDR).  That would be typical for ASTER. To create a temperature map from the ASTER data you could use these steps: 1. Open the ASTER image in ENVI using File > Open External File > EOS > ASTER. 2. Choose Basic Tools > Preprocessing > Calibration Utilities > Thermal Atmospheric Correction.  In the file selection dialog, choose the ASTER TIR bands (the fourth "image" opened by the ASTER reader).  Set the Wavelength Units to micrometers, and leave everything else at default values.  Enter an output filename, then click OK. 3. Choose Basic Tools > Preprocessing > Calibration Utilities > Calculate Emissivity > Reference Channel Emissivity or Emissivity Normalization.  Both of these tools can calculate emissivity and temperature values from your ASTER TIR radiance data. Peg