Using a new, high-temperature black-body radiator developed by the All-Russ
ian Institute for Optophysical Measurements (VNIIOFI), Moscow, and applying
newly developed methods and equipment, the black-body-based spectral irrad
iance scale of the Physikalisch-Technische Bundesanstalt (PTB), Braunschwei
g, has been extended and its uncertainties have been reduced compared with
previous results. The pyrolytic-graphite Planckian radiator BB3200pg, which
can be operated at temperatures up to over 3300 K, is presented and charac
terized along with modifications to optimize uniformity and stability. The
determination of the radiometric black-body temperatures is already well es
tablished by measuring the weighted irradiance using filter detectors witho
ut imaging systems. This method is compared and verified with results based
on self-consistent spectral irradiance measurements using fast-scanning sp
ectroradiometers. In addition, a laser-based method for the determination o
f the radiometric temperature is presented and compared with conventional p
rocedures of radiation-temperature measurement. The implementation of this
additional method into the radiometric chain of the PTB is illustrated. Imp
rovements in the uncertainty budget of the spectral irradiance scale are di
scussed.