ABSTRACT
Radiometry is the measurement of radiation. The conversion of photons of light to some sort of measurable signal is the purpose of radiometric detectors. Thermal processes include calorimetry and thermoelectric effects. Resistance temperature detector (RTD) relies on the change in resistance of certain materials as a function of temperature. Direct measurements of the relative intensity or magnitude of the circumsolar radiation show that within a few arc seconds of the edge of the solar disk, the number of photons falls off more than two or three orders of magnitude below the disk intensity. Photoelectric, or photodiode, pyranometer detectors suffer from Fresnel losses at the flat surface of the detectors themselves, as well as the surface of any flat window in the optical path to the detector. This chapter gives brief descriptions of the solar radiometer reference standard and one of the most important instrument characteristics that established during calibration.
