-Started development in the late 1960s -Line-by-line compilation of over 1,080,000 spectral line parameters for 36 different molecules -Parameters:line position, strength, half-width, lower energy level, etc. -Incorporated into LOWTRAN, MODTRAN, and FASCODE -Allow complex atmospheric transmittance and radience calculations -Based on absorption and scattering phenomena for a variety of pathgeometrics