Development And Application Of Vacuum Mercury Fixed Point Blackbody Source

As China continues to make new breakthroughs in the field of aerospace infrared remote sensing,the earth observation technology is developing in the direction of quantification,globalization,and multi-parameter collaborative observation.The requirements for quantification levels are stricter,especially in the fields of climate change,disaster prevention and mitigation,and numerical weather forecasting.For example,climate change monitoring requires that infrared remote sensing loads must meet a measurement uncertainty of better than 0.1 K(k = 3)and a stability of 0.04 K per decade.Such a high level of quantification poses new challenges to the development of infrared loads,and at the same time requires higher accuracy for the calibration of infrared loads.Therefore,it is particularly important to establish a measurement standard device that can be traced back to the International Unit(SI),achieve highprecision calibration of the calibration blackbody,and establish an effective value transfer system.The Chinese Academy of Metrology(China Institute of Metrology)has developed and established China's first vacuum low background infrared hyperspectral brightness temperature measurement standard device(VRTSF).By simulating the working environment of vacuum and low temperature in space,the device realizes the value traceability system from fixed point blackbody radiation source to variable temperature blackbody radiation source to user blackbody radiation source,which basically meets the calibration requirements of most infrared remote sensing loads in China.This article mainly introduces the development process of vacuum mercury fixed point black body radiation source(mercury black body)in VRTSF system and the application of mercury black body in VRTSF system.The structure design,working principle,thermal simulation analysis,performance test and test result analysis of the mercury black body are expounded,and the uncertainty of the mercury black body is analyzed.Finally,the brightness temperature of the mercury blackbody on the phase change platform was measured in the VRTSF system.The working temperature of the vacuum mercury fixed point black body radiation source is 234.316 K,and the high purity mercury with a purity of 99.9999% is poured.The black body cavity opening diameter is 25 mm,the cavity inner diameter is 28 mm,the depth is 260 mm,and the surface is sprayed with NEXTEL 811-21 high emissivity coating,using the method based on Monte Carlo black body emissivity simulation calculation,calculated the emissivity of the black body cavity at a wavelength of 8 ? 14 ?m,the result is better than 0.9999.The three-dimensional software was used for three-dimensional modeling of mercury fixed-point blackbody radiation sources,and the simulation software was used to simulate the heat transfer performance of mercury fixed-point black body radiation sources.The results show that the temperature uniformity of the black body cavity of the fixed point black body radiation source at steady state is better than 20 m K,and the transient temperature uniformity is better than 1 m K.In a vacuum environment,the main technical indicators such as the temperature plateau and repeatability of the black mercury radiation source at a fixed point of vacuum mercury were tested.The results show that the stability of the temperature plateau of vacuum mercury fixed point blackbody radiation source is better than 2 m K,and its repeatability is better than 1 m K.The sources of uncertainty of vacuum mercury fixed point black body radiation sources are analyzed,and the synthesis standard uncertainty is calculated to be 16 m K.Finally,the brightness temperature of the mercury blackbody on the phase change platform was measured in the VRTSF system,and the experimental results were analyzed.The successful development and application of the mercury fixed-point blackbody radiation source has perfected China's vacuum low-background infrared brightness temperature measurement standard device,and realized the value transfer system from the fixed-point blackbody radiation source to the variable-temperature blackbody radiation source to the user's blackbody radiation source.The improvement of the level of infrared remote sensing in China provides a strong technical support.