The earth background radiation is an important factor in the detection of space to earth, since it is necessary to study the influence of different surface on infrared detection. In this research, the daytime atmospheric meteorological data of 2021 summer solstice in typical areas of China are measured by multichannel infrared radiometer SABER(Sounding of the Atmosphere using Broadband Emission Radiometry). Calculated the infrared background radiation with a wavelength of 1-6 μm, at a same time, compared the results of the measured data in the South China Sea with the results of the Standard data. The calculation results show that the difference in the earth background radiation calculated by the standard in different regions is not obvious. The atmospheric data can more accurately reflect the earth background radiation of different surface types. At the time, in different regions the earth background radiation is mainly concentrated in the 1-2.5 μm band, the infrared background radiation in desert and forest region is stronger than that in snow mountain region, and the radiation intensity in ocean region is weakest.
The flow field around the hypersonic vehicle is in a thermodynamic and chemical non-equilibrium state when it reenters the atmosphere. The excited state level number density of the molecular atoms no longer satisfies the Boltzmann distribution in the thermochemical non-equilibrium state. In order to accurately calculate the spectral radiation characteristics of NO (A2Σ+), a collision-radiation (C-R) model coupled with N2 is used to consider the excited state population from the microscopic process of its level transition in this paper. HITRAN 2020 database and line-by-line (LBL) method are used to calculate the high-resolution spectral absorption coefficient. And then combined with the line of sight (LOS) method, the ultraviolet (UV) spectral radiation produced by the NO (A2Σ+ ) is calculated. The translational temperature, vibration temperature and two-temperature model are used to characterize the reaction rate retrospectively so as to obtain the NO excited state number density and UV spectral radiation under thermodynamic and chemical non-equilibrium states. The shock layer experiment of BSUV with a flight altitude of 38km and speed of 3.5km/s is taken as an example, the effect of different characterization temperatures on spectral radiance is analyzed and the optimum characterization temperature of NO (A2Σ+ ) non-equilibrium UV radiation is obtained. The results show that characterizing the NO(A) number density with the translational temperature, rather than the vibrational temperature and two-temperature model, yields a better comparison to the flight experimental data.
The ultraviolet radiation generated by NO transition in the shock layer of hypersonic vehicle provides an important basis for target detection and recognition. In this paper, direct simulation Monte Carlo (DSMC) method is used to simulate the high temperature flow field of the Apollo aircraft. Based on the temperature, pressure, and mass fraction, SPECAIR software is used to calculate the NO(γ) spectral absorption coefficient, and combined with the line of sight (LOS) method, the ultraviolet radiation produced by the NO(γ) transition along the stagnation line at different heights is calculated. Based on the wall heat flux, the wall energy conservation equation is used to calculate the wall temperature, combined with the Planck's law to calculate the wall radiation, and the influence of the wall catalytic effect on the ultraviolet radiation is studied. The results show that with the increase of the height, the gas pressure and temperature decrease obviously, and the ultraviolet radiation from NO(γ) transition decreases. The wall heat flux calculated by the wall catalytic model is very different. The choice of the wall catalytic model is particularly important when studying the influence of the wall radiation on the ultraviolet radiation.
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