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Miniature fixed-point blackbody (MFPB) can realize the on-orbit calibration of temperatures by tracing the miniature fixed-point. This ability can effectively improve the precision and life span of earth observation systems. Researchers have verified the feasibility of the MFPB in engineering through experiments. However, the temperature relationship between the miniature fixed-point and the blackbody is unclear at present, which means that the transfer relationship between radiation temperature of space infrared radiation standard source and international temperature scale cannot be established accurately. In this article, a temperature transfer relationship between miniature fixed-point and blackbody in MFPB is established, and the temperature transfer equation (TTE) is proposed to obtain the run-off point temperature of blackbody (RPTB). The effects of heating power and ambient temperature on the temperature transfer relationship between miniature fixed-point and blackbody are investigated numerically. Retrieval results show that a linear relationship exists between the RPTB and the heating power and ambient temperature in a single fixed-point temperature range. The TTE is obtained and explained theoretically. All experimental results of the gallium fixed-point are in good agreement with this equation. Furthermore, the RPTBs are accurately predicted at gallium-stannum and H2O fixed-points by TTE. The average and maximum errors are 0.0044 and 0.0063 K, respectively. The current study is of considerable importance to the development of MFPB technology and improvement of the on-orbit infrared remote sensor calibration.

Low size-of-source effect (SSE) infrared optical system design and experimental validation are critically involved. SSE is commonly explored in infrared radiation measurements. The main causes of SSE are the diffraction of the field aperture, the reflection of optical components and objective aberrations. The optical path design and the internal components scattering have an important influence on SSE. Reflective optical system is commonly used in infrared radiation measurements with high temperature region and wide wavelength range, which can eliminate chromatic aberration and reduce coma. A reflective infrared optical system is designed and built based on the high-temperature Fourier transform infrared (FTIR) spectrometer infrared radiation measurement facility at NIM. The ambient scattered radiation and the thermal effect of optical components are controlled via the water-cooled scattered radiation shielding bin and limitation apertures. Experimental validation of the SSE characteristics of the FTIR infrared optical system is carried out via the uniform blackbody radiation source at 500 °C and various sized apertures using the direct measurement method. The corresponding calculation model will be described in the paper. SSE on 3.9 μm is measured via the direct measurement method by using a standard reference blackbody with good temperature uniformity as the radiation source. The effect of reflection is reduced via the high emissivity coating on the apertures. The results show that the effect of the SSE on the FTIR measurement facility at the wavelength of 3.9 μm is less than 2×10-4. Details and results of the infrared optical system SSE measurement will be reported in the paper. All measurements can be traceable to the National Standards of P. R. China.

Integrated blackbody is a blackbody radiation source with the emissivity approximate to 1, which is coupled of materials with different infrared emissivity as the cavity wall and the cavity bottom. The integrated blackbody theory is the theoretical basis of materials infrared spectral emissivity measurement device at ultra-high temperature developed by National Institute of Metrology, China (NIM). Infrared emissivity is the most important factor for evaluating the infrared radiation characteristics of integrated blackbody. Based on Monte Carlo simulation, infrared emissivity of the integrated blackbody coupled of different high emissivity materials and infrared emissivity of the integrated blackbody coupled of low emissivity material and high emissivity material are calculated theoretically in the near infrared wavelength band at room temperature and high temperature environment. The simulation results show that, the infrared emissivity of the integrated blackbody coupled of different high emissivity materials can reach 0.998 and the infrared emissivity of the integrated blackbody coupled of low emissivity material and high emissivity material can reach 0.988. The above simulation results of integrated blackbody infrared emissivity have reached the requirements of industrial blackbody radiation source. The simulation results are verified based on the method of blackbody infrared emissivity measurement by integrating sphere reflectometer at room temperature environment at wavelength of 0.633 μm. Measurement results on multiple wavelengths show that the deviation between the integrated blackbody infrared emissivity simulation results and the measurement results is less than 0.3 %.

Miniature fixed-point blackbodies (MFPBs) can realize the on-orbit multipoint temperature calibration through the known characteristic temperature. This ability is important for improving the precision and life span of earth observation systems. For acquisition of characteristic temperature, numerical simulation has lower cost and test condition requirements. However, ordinary numerical models can’t meet the accuracy requirements of MFPB. The purpose of this paper is established an accurate numerical model for characteristic temperature acquisition of miniature fixed-point blackbodies. A novel thermal resistance equivalent corrected method (TRECM) is proposed in accordance with the difference between the numerical model and actual experiment. The equivalent correction of the total thermal resistance between two temperature points is achieved by correcting a certain term of thermal resistance in the heat flow transfer path. The TRECM can effectively replace the detailed structure, complex surface radiation and unknown parameters. Characteristic temperatures of blackbody are obtained during Ga, Ga-In, and H2O phase transitions at different heating powers by using proposed model. Meanwhile, an experimental system is established to validate the model. The results showed that the average model error of characteristic temperature between the calculated results and the experimental results decreased from 77.2 m K to 6.2 m K by the TRECM.

Blackbody cavity reflectivity is normally measured using an integrating sphere to collect hemispherical reflected radiation from a blackbody opening when illuminated by a directional light source. The challenge of taking this method without an integrating sphere arises for blackbody cavity emissivity measurement in satellites due to space constraints. The ratio of hemispherical–given solid angle reflections is proposed to calculate the total reflected power from a blackbody cavity by multiplying a measurable reflected power in a given solid angle. The ratio is obtained by simulating the distribution relationship between the total hemispherical reflected light power and the reflected light power in the given solid angle under different coating emissivity. The emissivity measurement results are consistent with radiometric method measurements and simulation results, with an uncertainty of 0.0005.

Spectral emissivity is one of the most critical thermophysical properties of a material for heat design and analysis. Especially in the traditional radiation thermometry, normal spectral emissivity is very important. We developed a prototype instrument based upon an integral blackbody method to measure material’s spectral emissivity at elevated temperatures. An optimized commercial variable-high-temperature blackbody, a high speed linear actuator, a linear pyrometer, and an in-house designed synchronization circuit was used to implemented the system. A sample was placed in a crucible at the bottom of the blackbody furnace, by which the sample and the tube formed a simulated reference blackbody which had an effective total emissivity greater than 0.985. During the measurement, a pneumatic cylinder pushed a graphite rode and then the sample crucible to the cold opening within hundreds of microseconds. The linear pyrometer was used to monitor the brightness temperature of the sample surface, and the corresponding opto-converted voltage was fed and recorded by a digital multimeter. To evaluate the temperature drop of the sample along the pushing process, a physical model was proposed. The tube was discretized into several isothermal cylindrical rings, and the temperature of each ring was measurement. View factors between sample and rings were utilized. Then, the actual surface temperature of the sample at the end opening was obtained. Taking advantages of the above measured voltage signal and the calculated actual temperature, normal spectral emissivity under the that temperature point was obtained. Graphite sample at 1300°C was measured to prove the validity of the method.

Spectral emissivity is a critical material’s thermos-physical property for heat design and radiation thermometry. A prototype instrument based upon an integral blackbody method was developed to measure material’s spectral emissivity above 1000 ℃. The system was implemented with an optimized commercial variable-high-temperature blackbody, a high speed linear actuator, a linear pyrometer, and an in-house designed synchronization circuit. A sample was placed in a crucible at the bottom of the blackbody furnace, by which the sample and the tube formed a simulated blackbody which had an effective total emissivity greater than 0.985. During the measurement, the sample was pushed to the end opening of the tube by a graphite rod which was actuated through a pneumatic cylinder. A linear pyrometer was used to monitor the brightness temperature of the sample surface through the measurement. The corresponding opto-converted voltage signal was fed and recorded by a digital multi-meter. A physical model was proposed to numerically evaluate the temperature drop along the process. Tube was discretized as several isothermal cylindrical rings, and the temperature profile of the tube was measurement. View factors between sample and rings were calculated and updated along the whole pushing process. The actual surface temperature of the sample at the end opening was obtained. Taking advantages of the above measured voltage profile and the calculated true temperature, spectral emissivity under this temperature point was calculated.

Recent international comparisons [1,2] and key comparisons have shown that the realization of the International Temperature Scale of 1990 (ITS‐90) above the freezing point of silver and its dissemination is more difficult than expected. In many cases, the deviations of the local scale realizations were larger than the combined estimated uncertainties could reasonably justify. On the other hand, it must be considered that the realization of the ITS‐90 by radiation thermometry is a complex exercise involving a large number of operations with many influencing parameters. Furthermore, the key comparisons need a unified approach to the treatment of uncertainties. Consequently, a rigorous standard approach for the calculation of uncertainties is necessary. In this paper three different operational schemes have been identified for realizing the ITS‐90 by radiation thermometry. For all three schemes an analysis is presented of the baseline parameters underlying the scale realization above the freezing point of silver with respect to their contribution to the uncertainty budget. The paper is a joint effort of the working group on radiation thermometry of the Consultative Committee for Thermometry (CCT) summarizing the knowledge and experience of all experts in this field.

This paper presents the design and construction of a new type of precise photoelectric pyrometer, a transfer standard in the range of 800 °C to 3200 °C. The modified calibration methods have been applied at NIM to improve the dissemination of the ITS‐90 with the new pyrometers. A resolution at the copper point of approximately 1 mK and an estimated standard uncertainty of 0.22 °C to 0.8 °C from 800 °C to 2200 °C were obtained. Comparison measurements performed between the pyrometers and primary standard lamps from 800 °C up to 1700 °C show agreement within 0.3 °C.