Developments for a new spectral irradiance scale at the National Institute of Standards and Technology

Recent developments for a new spectral irradiance scale realization at the National Institute of Standards and Technology have been targeted to reduce the present relative expanded uncertainties of 0.67 % to 4.34 % (coverage factor of k = 2 and thus a 2 standard deviation estimate) in the spectral irradiance scale to 0.17 % for the range from 350 nm to 1100 nm. To accomplish this goal, a suite of filter radiometers calibrated using NIST's high accuracy cryogenic radiometer have been used to measure the temperature of a high-temperature blackbody. A comparison of the filter radiometer calibrations with the spectral irradiance scale along with an evaluation of the blackbody calibration technique have been performed. With the aid of a monochromator, the calibrated filter radiometers will then be utilized to calibrate primary and secondary spectral irradiance standard lamps at NIST.