ENVI does not contain the spectral response function for the ALI sensor.  It looks like the tables for it can be found here: http://www.eoc.csiro.au/h...w/oz_pi/specresp.htm You will need to create a spectral library from the information in the spreadsheet in order to use it in FLAASH. Alternately, you can use QUac to perform the atmospheric correction which does not require this information.