A One-Solar-Constant Irradiance Standard

A new high-intensity standard of total and spectral irradiance has been developed recently at the National Bureau of Standards. The standard consists of a 1000-W tungsten-halogen lamp mounted in a ceramic reflector, the reflecting surface of which is coated with flame-sprayed Al(2)O(3). The lamp-reflector combination results in a source having a relatively small (3 cm x 5 cm) radiating area yielding a total irradiance, at a distance of 40 cm, of about 136 mW cm(-2). The total irradiance calibrations are based on the radiance of a 1400-K blackbody and have an estimated maximum systematic error of 0.9% and a maximum estimated standard error of 0.19%. The spectral measurements were made over the wavelength range of 0.3 microm to 2.5 microm relative to the NBS 1000-W tungsten-halogen irradiance standards. The estimated uncertainty in these measurements ranges from 4% in the visible and near ir to 8% in the uv.