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

Abstract

The issues of radiometric calibration of optical-electronic equipment for remote sensing of the Earth in a wide range of spectral radiance have been studied. An alternative method for transmitting a spectral radiance unit from a reference source at the phase transition temperature of pure metals to optical-electronic equipment for remote sensing of the Earth in the infrared wavelength range above 2.5 μm is presented. 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 level of emissivity and a wide temperature range identical to the temperature range of a wide-aperture black body model with a range of spectral radiance required for calibrating optical-electronic equipment for remote sensing of the Earth. A precision black body model PMBB-60m with an output aperture with a diameter of 30 mm was developed, studied and calibrated in the temperature range of 200–450 K. The calculated value of the effective emissivity of PMBB-60m with coating of the cavity by Aeroglaze Z306 paint is 0.9997. The composition and design of PMBB-60m are described. PMBB-60m can operate both in vacuum conditions and in 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 digit of a temperature unit in the range from 0 to 3000 °C using a comparator, based on a precision pyrometer TRT II (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 according to the results of calibration in the temperature range of 223.15–450.15 K. The results of calculating the expanded uncertainty in the temperature range of 223.15–450.15 K did not exceed 1 K. The values of instability of temperature maintenance PMBB-60m, measured in steps of 10 s for 15 minutes, did not exceed 15 mK in the considered temperature range. The results of calculation of the spectral effective emissivity of PMBB-60m, carried out using the STEEP3 program, are presented.