the help file on this seems to contradict itself. This is the description for the input wavelength keyword: I_Spec A one-dimensional array of input spectra to be resampled. "One-dimensional array" seems to imply a single spectrum, but the word "spectra" being plural clearly implies more than one spectrum. Three other keywords (I_wl, O_wl, and O_spec) all say the same thing as this. Also, if the routine only operates on one spectrum at a time, and returns one spectrum at a time, why is there an interleave keyword? Jeff