Realization of relative responsivity scale with the electrically calibrated pyroelectric radiometer

In UME, the relative spectral responsivity scale extending from 250 to 2500 nm was realized using electrically calibrated pyroelectric radiometer (ECPR). Its absolute spectral responsivity was determined against the electrical substitution cryogenic radiometer (ESCR) facility at 488.1, 514.6, 532.0, and 632.8 nm with an uncertainty of 1 part in 10⁴ (k=2). The relative spectral responsivity scale of ECPR was derived from the surface reflectance data and absolute spectral responsivity data for the mentioned spectral range. Optical characterization of its spatial non-uniformity (at 632.8 nm) and surface reflectance (over 250–2500 nm wavelength region) indicated that the gold-black absorber is spectrally flat within 0.1%. The total expanded uncertainty in the realization of the mentioned radiometric scale along with ECPR was estimated as 1.74%.