I think the first thing to check is to make sure that you have spectral information in your field/reference spectra for whateve wavelength range is contained in ASTER band 9. If your "known" spectrum doesn't contain spectral information at the wavelength of your band 9, I wouldn't be surprised to see the effect you're getting b/c you'd be multiplying the input data (ASTER) by zero for that particular wavelength I think. I'm pretty sure ENVI's empirical line routine will interpolate between wavelengths if it needs to, but i don't know about extrapolating to one. I could be completely wrong about this, however, b/c I would think that the routine would issue a warning or an error message if you didn't have matching wavelengths. Jeff