Precision black body model at a temperature range of 200–450 K: metrological assurance for optical-electronic equipment for remote sensing of the Earth in the infrared range of the spectrum

We discuss challenges in radiometric calibration of optical-electronic equipment for Earth remote sensing (ERS) over a wide range of spectral radiances. An alternative method is presented to transmit a spectral radiance unit from a reference source (black body model, BBM) at the phase transition temperature of pure metals to optical-electronic equipment for ERS in the infrared range above 2.5 pm. The method is based on the stepwise transfer of a spectral radiance unit from a reference source through a precision model of a black body with a high emissivity level and wide temperature range identical to the temperature range of a wide-aperture BBM with a range of spectral radiance required for calibrating optical-electronic equipment for ERS. A precision BBM PMBB-60m with an output aperture with a diameter of 30 mm is developed, investigated, and calibrated in the temperature range of 200–450 K. The calculated value of the effective emissivity of PMBB-60m with the cavity coated with Aeroglaze Z306 paint is 0.9997. The composition and design of PMBB-60m are described. Such a precision BBM can operate both in vacuum and under conditions of inert gas or atmospheric pressure. The metrological characteristics of PMBB-60m, obtained by transferring a temperature unit from the State Standard of the zero bit of a temperature unit in the range of 0 °C–3000 °C 3.1.ZZA.0020.2015 using a comparator based on a TRT II precision pyrometer (Heitronics Infrarot Messtechnik GmbH, Germany) are presented. The correction to the PMBB-60m temperature readings in the temperature range of 223.15–450.15 K did not exceed 39 mK based on the results of calibration in the temperature range of 220–450 K. The results of calculating the expanded uncertainty in the temperature range of 223.15–450.15 K did not exceed 1 K. The instability values of the temperature maintenance of PMBB-60m, measured in steps of 10 s for 15 min, did not exceed 15 mK in the considered temperature range. The calculation results of the spectral effective emissivity of PMBB-60m using the STEEP3 program are presented.