Hello Enrique, The main difference with ASTER L1B and L1T is that the scale factors are *not* automatically applied to ASTER L1T so the data are still in byte values. You can use the Radiometric Calibration tool to convert the SWIR and TIR bands to TOA radiance (and for SWIR you can also calculate TOA reflectance). Once the TIR bands are in the expected radiance units of W/m^2*sr*um then you can input this data to the Emissivity tools that are available. What do you want to do with the SWIR bands? With the Radiometric Calibration tool, you can calculate radiance or TOA reflectance. If you plan on applying an Atmospheric correction with FLAASH/Quac, you would want to calibrate to radiance and then use FLAASH/Quac to calculate surface reflectance. I typically would stack the VNIR-SWIR radiance bands into a single cube (resampling to the VNIR pixel size) prior to applying the atmospheric correction. - mari

Hello Mari, many thanks for your kind and prompt reply, best regards Enrique

Hello Mary, I use Radiometric Calibration to calibrate into radiance TIR Bands in ASTER L1T, you mention that then you can use Emissivity tools in ENVI, is not necesary to use previous a "Thermal Atmospheric Correction"?

best regards
Jose Manuel Lattus

You are correct. It is suggested that for best results you first perform an atmospheric correction before conversion to emissivity.