Get 48-2018 State Primary Standard of the Unit of Infrared Radiance

The paper considers stages in the development and improvement of high-level measurement standards that provide metrological support to radiance measuring instruments while outlining principles that underlie the realization and transfer of the radiance unit. Increased requirements for the metrological support of radiance measuring instruments led to the creation of GET 48-2018 State Primary Standard of the Unit of Infrared Radiance. The authors describe GET 48-2018 and its constituent emitters, i.e., blackbodies (BB), employing the phase transitions of pure substances (mercury, water, gallium, indium, tin, zinc, aluminum, and copper), as well as radiometer-comparators used to transfer the radiance unit to working standards and measuring instruments. The design of BB emitters and equipment needed to create the required temperature conditions are considered. The conducted studies revealed the long-term stability and high reproducibility of BB emitters developed on the basis of the fixed points of pure substances. In order to increase sensitivity and reduce noise in the radiometer-comparators, the optical design was improved, modern opticalacoustic detectors (Golay cells) were installed, and lock-in amplifiers were used to process the measured output signal of radiation detectors. This factor allowed the error in transferring the radiance unit to be reduced.

The conducted studies aimed at maintaining the current scientific and technical level of metrological characteristics of GET 48-2018 and its constituent parts confirm that the reproduced radiance values are as follows: 54.36; 100.39; 151.80; 614.96; 1173.4; 4151.0; 13691; 61282 W/(sr∙m²) with an expanded uncertainty of no greater than 1.5·10⁻³ relative units. GET 48-2018 is currently at the top of the metrological support system for radiance measuring instruments widely used in the defense industrial sector, life support, space exploration, and environmental protection.