if you just go to file -> edit ENVI header a dialog box will open up. In that dialog box, go to the Edit Attributes pull down menu and choose Wavelengths.... You can add them manually or import a text file. Thats how to assign the values, for where to get the values in the first place, consult your Landsat documentation, or you might be able to find it on the web, or you might even be able to use the bandpass functions in the filt_func directory if you're clever enough - as in, take a high resolution spectral library, convolve it to Landsat bandpasses, and note the resulting wavelength positions. Note, however, that I suppose it's possible (though probably unlikely) that the calibration/georectifications changed wavelength position values slightly. Jeff