A far infrared spectral irradiance standard radiator has been developed. It consists of a 20-mm diameter, 40mm-long silicon carbide tubular heater and an aperture consisting of a double structure of aluminum plates. The surface temperature of the radiator is about 920K peak radiation wavelength is about 3.1μm and consumption power is 400W. The relative spectral irradiance was calibrated against a silicon carbide cavity (black body) radiator of the same type. The absolute irradiance value was determined by measuring the total irradiance using a broad bandpass filter and a thermal detector (thermopile) at a wavelength of 1. 5-4μm and by measuring the spectral irradiance of an ETL halogen lamp standard at 1. 5 2.5μm. These two methods gave results that agreed within 3%. The irradiance at a distance of 400mm were 0.2mW·cm-2· nm-1 at 1.5μm, 1.3mW·cm-2·nm-1 at 3μ, and 0.04mW·cm-2· nm-1 at 12μm. The change in spectral irradiance was less than 1.5% after 100 hours of operation.
