In 2000, the American Society for Testing and Materials developed an AM0 reference spectrum (ASTM E-490) for use by the aerospace community [RD.33]. That ASTM E490 Air Mass Zero solar spectral irradiance is based on data from satellites, space shuttle missions, high-altitude aircraft, rocket soundings, ground-based solar telescopes, and modelled spectral irradiance. The integrated spectral irradiance has been made to conform to the value of the solar constant accepted by the space community; which is 1 366,1 W m-2. Figure F-1 shows the solar irradiation spectrum at AM0 and AM1.5.